Improvised oscilloscope probe for Automotive ignition analysis. - Page 1
Forum section: electronics / projects

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 03, 2019, 08:31:47 pm
content: A stock car racing buddy has a miss firing engine in his race car. We would like to put an oscilloscope on the high tension leads. At present, the ignition system is the standard, pre-EFI, contact points and capacity, Kettering System.It did have (and will have again) electronic ignition, but this has been replaced with the above in the fault elimination sequence that has been done to try and locate the fault. A lot of stuff on the engine has been swapped and replaced in the search for the miss.The car miss fires most under load; classic HT breakdown behavior.In the attached document from "Electronics Today" 1977, an improvised high ratio probe is described using a common peg and some aluminium foil. This then, allegedly, enables a more common low max voltage oscilloscope to be used with safety.My questions:Is this a safe way to protect the oscilloscope?If so, should it be tested somehow before plugging it into a high tension lead?Or is the probe simply wrapped around the outside of the HT ignition lead?It is hard to tell how this probe is made. If someone reading knows, please advise?I do hope this is the best section of the forum to post this. If not, please advise and re-direct me.Jim.

author: soldar
author_rank: Super Contributor
timestamp: January 03, 2019, 10:33:13 pm
content: The sensing is done capacitively by wrapping a bit of metal around the HV cable.Those ignition systems are fairly straightforward. Things to check are that points and capacitor are good, coil is good (they do fail), coli polarity is connected correctly, HT cables are good and spark plugs are good. All are easy to test and with all things being as they should I can't think of anything else which could go wrong. I guess the distributor but that is less likely or it would be obvious.All cylinders have the same problem?I do not understand something. The electronic ignition has been replaced by the older Delco? How are you going to diagnose the electronic with the Delco? And both are misfiring in the same way?You are not using the same coil are you? Again, try replacing the coil and make sure of the polarity.

author: Microcheap
author_rank: Frequent Contributor
timestamp: January 03, 2019, 10:49:05 pm
content: On Aliexpress you can find this capacitive probe used to test the secondary of the ignition as is described in the article you linked:https://www.aliexpress.com/item/Hantek-HT25-Automotive-Oscilloscope-Probe-HT25-2-5-meters-Ignition-Capacitive-decay-of-up-to-10000/32822817192.htmlthere is another type of probe but I've never tested onehttp://www.hantek.com/en/ProductDetail_15_11165.html

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 04, 2019, 01:05:34 am
content: Quote from: soldar on January 03, 2019, 10:33:13 pmIs the normal probe just connected to the metal film?QuoteThe two brothers who are working on it are both career mechanics. They have changed all the above parts more than once, and some, like the spark plugs more times than they can count. They have fabricated a new inlet manifold and fitted a different carburettor. They even changed the camshaft. For a while, the cylinders were behaving differently, with #6 cylinder missing more than others. Then they turned the carb around 180 degrees and the cylinders now (appear) to behave similarly. Coils changed, new capacitor and points fitted to the present Kettering ignition system. etc. etc.This might give you a bit of an idea into the recent history of this Holden Grey motor. Much modified I should say.The engine missfires with both ignition systems in the same way.I have suggested the ignition analysis. And, also, running the engine in the dark of night. Observe for sparks etc. However, it is possible to hold all ignition leads while the engine is running, suggesting all insulation is sound.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 04, 2019, 01:06:57 am
content: Quote from: Microcheap on January 03, 2019, 10:49:05 pmThanks for that link. I will follow it up.

author: Johnny10
author_rank: Frequent Contributor
timestamp: January 04, 2019, 01:24:57 am
content: The best way to test for problems in firing is with an oscilloscope.A HT probe on the sparkplug wire and a pressure transducer in the cylinder hooked to oscilloscope.This will show where in the cycle spark happens and the position of valves in the cycle.It will show advanced or retarded firing.This was my first oscilloscope project.The pressure transducer signal identifies all the engines internal pressures during the combustion cycle. The HV spark signal shows where the spark ignites fuel as a second channel.https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1004&context=auto_presThese should get you started.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 04, 2019, 01:31:14 am
content: Quote from: Johnny10 on January 04, 2019, 01:24:57 amPressure transducer? That is new to me, can you please explain Johnny.QuoteI will download them and watch them.Thanks,Jim.

author: David Hess
author_rank: Super Contributor
timestamp: January 04, 2019, 02:24:57 am
content: Quote from: Jim-0000 on January 03, 2019, 08:31:47 pmAt high compression the breakdown voltage across the spark plug is greater so if the voltage is low, it is more likely to miss.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 04, 2019, 02:53:35 am
content: A home made probe for looking at the ignition waveform.Hunting a problem that only happens under load is always fun. Keep in mind it may have nothing to do with the electrical or electronics at all.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 04, 2019, 03:17:58 am
content: Quote from: joeqsmith on January 04, 2019, 02:53:35 amThat is interesting. Can you provide some more details please Joe?What cable you use, where to get it etc.Is the attenuation sufficient enough to plug it into a small oscilloscope with a 200 volt input max limit?QuoteOf course, that has been the awareness all along. Evidenced by the many changes and mods done, some of which I listed above.Thanks for the picture and the comment.

author: floobydust
author_rank: Super Contributor
timestamp: January 04, 2019, 03:42:59 am
content: I've had similar weak spark problems on my old musclecar and none were in the textbook.You can look at the HT waveforms but you've replaced everything there, so the problem is likely elsewhere.Some things to check:1. It was a defective manufacturing batch of Champion spark plugs, the internal resistors were pooched/missing and the arc was inside the porcelain making up for that.2. Problem was the tachometer, its input circuit was loading the coil primary.3. The ballast resistor - it was nichrome wire in the harness, partially broken so a high ohms value.4. A set of points with a weak spring, the contacts bounced at anything much above idle RPM's.5. I would look at dwell and see if the distributor is stable - one had loose bearings and the shaft wobble changed dwell at speed and it was very hard to track down.I would check the 12V feed to the ignition system is not sagging, and you are (now) using a ballast resistor/condenser with points?... so as to not damage the coil. Transistorized ignition does not need the ballast resistor, and move the condenser to the 12V power input.Most digital scopes can't handle automotive ignition systems. The EMI will make the scope add false signal spikes and noise to the displayed waveform. So be prepared to go on a goose chase looking for a "blip" on the waveform that actually isn't there.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 04, 2019, 04:19:00 am
content: Quote from: floobydust on January 04, 2019, 03:42:59 amPoint #4 is not likely, as they are new points.But............Point #5 might be the problem! They are using an old Holden grey motor distributor. (however, come to think of it, they did have a Falcon distributor in it with the electronic hall sensor type ignition.........same problem exhibited).QuoteThat is what one of the mechanic (brothers) is going to check first opportunity on Sunday. He will power the ignition system only with a separate battery and cables. The car battery is in the back of this Stock car, so there is a long wiring loom. Potential there for voltage drop as you mention and/or one or two poor connections. Also, there is a "kill" safety switch on the dashboard!QuoteNo ballast resistor during the last iteration of the ignition system. In other words, the last time we worked on it. Might have had one previously.Thanks for the detailed reply.Jim.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 04, 2019, 04:38:21 am
content: Coax is RG400/U. I have a trimmer cap up near the clamp to trim the voltage level. The large braid goes to the block, the clamp goes around the plug wire. As mentioned, this forms a capacitive divider. I feed this into a 50 ohm termination (built into the scope). I test the ignition parts off the engine.

author: tautech
author_rank: Super Contributor
timestamp: January 04, 2019, 07:09:32 am
content: Things to double check:Battery to chassis and engine block grounds.Coil ground.Points plate ground.Broken cable conductors, typically old cabling where bending forces have broken the internal strands.Cracked dizzy cap or rotor.Dicky carbon and/or spring in the dizzy cap.

author: vk6zgo
author_rank: Super Contributor
timestamp: January 04, 2019, 07:49:32 am
content: Quote from: tautech on January 04, 2019, 07:09:32 amAll of the above!Plus, if you are using suppressor leads, check that they are around 15 to 20 k resistance.Back in the day, when the carbon core looked pretty much like burnt string, it was not unusual to find one' or more leads had drifted up to 5 megohms or so.Sparkplugs are not all equal, even when they have the same part number & brand.I fitted a set of German made Bosch spark plugs to my HQ Holden 6 back in the day----should have been good, eh?Nope, the insulators cooked up, went brown, & started leaking badly.The same number but made by Bosch in Australia were noticeably different, in that the insulation was thicker where it went into the metal body of the plug.It turned out that there were two plugs using that part number, one which was designed for aluminium heads, & the other for cast iron ones, with their worse heat dissipation.The "aluminium head" ones were never meant to be sold in Oz.Holdens fitted AC Delco Spark Plugs as standard, & crappy things they were, too!My HQ had just run over the time for the last warranty service, so I fitted (Oz made) Bosch plugs, thinking that as I would have to pay for spark plugs anyway, they might as well be the ones I like.I ran into an acquaintance who worked at the Holden dealer, who said "You are only a "bee's whisker" over, bring it in!"Well, I thought I had a win, till the next week I was travelling down to a country town about 200km away from home, when suddenly, there was an almighty "bang" followed by "chuffing" noises.The entire insulator & "guts" of one spark plug had been blown out, never to be seen againOn investigation, I found the dealer had removed all my beaut new Bosch plugs , fitting AC "crappo" ones instead!

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 04, 2019, 08:18:25 am
content: Quote from: tautech on January 04, 2019, 07:09:32 amAll good points and all will be checked again this Sunday. I hope to be assisting.I suspect point #1 the most. Battery is in the back, as I have explained.The distributor earthing is another one we will check, (I hope).

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 04, 2019, 08:22:24 am
content: Quote from: joeqsmith on January 04, 2019, 04:57:59 amI have already linked it in the first post. Very good paper from 1977.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 04, 2019, 08:23:20 am
content: Quote from: joeqsmith on January 04, 2019, 04:38:21 amWhere did you buy the clamp please Joe?

author: tautech
author_rank: Super Contributor
timestamp: January 04, 2019, 08:27:04 am
content: Quote from: Jim-0000 on January 04, 2019, 08:18:25 amSome points plates used a slipper contact while others used a very fine and soft braid or wire. If intact they give no problems but a slipper contact can if the wiper hasn’t enough tension.Good hunting.

author: soldar
author_rank: Super Contributor
timestamp: January 04, 2019, 08:30:20 am
content: If the spark has enough voltage, and it should, and it only fails under load, that means is is not high enough to spark through the compressed mixture or it is sparking somewhere else. Some spark plugs can be defective and the spark jump internally. Or if the plug's cap are not good the spark can be jumping totally outside the plug directly to the block. Or it can be inside the coil. But you say all these items have been replaced....Yeah, it's no fun troubleshooting something which happens only under heavy load.

author: tautech
author_rank: Super Contributor
timestamp: January 04, 2019, 08:36:14 am
content: Quote from: soldar on January 04, 2019, 08:30:20 amDepends on how hardcore your setup is.Add some logging to a race car and examine a pass and the issues generally stand out like a sore toe !

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 04, 2019, 08:54:22 am
content: QuoteCan you explain what this means to a "non racecar" experienced, but otherwise generalist mechanical person please?(I have maintained my own road vehicles for over 60 years. The very few times I went to a mechanic in remote locations etc., the job was not done properly!)So I sympathise with vk6zgo in reply #13.

author: tautech
author_rank: Super Contributor
timestamp: January 04, 2019, 09:20:24 am
content: Quote from: Jim-0000 on January 04, 2019, 08:54:22 amFull logging of all systems can get pretty complex with sensors all over the vehicle and they can help fine tune most of a cars performance. All I’ve had experience with are on door slammer drag cars but one of the most telling are EGTs that not only give feedback on tune vs load but when they might drop unexpectedly against another cylinder indicating what’s generally an ignition problem.They are great when doing dyno runs to optimise tune at all points over the rev range.So what might you log ?RPMBoostFuel pressureTPSDriveshaft RPM (slider clutch slippage)Suspension (launch squat and bumps in the pass)Battery voltage etc etcFor the guys right into it, logging is of paramount importance to squeezing what’s possible out of any setup.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 04, 2019, 01:03:10 pm
content: Quote from: Jim-0000 on January 04, 2019, 08:23:20 amA friend of mine had given me a couple of those. As the paper mentions, a clothespin would work fine.Quote from: tautech on January 04, 2019, 09:20:24 amA few others I look at are: EGT, exhaust pressure, oil pressure, AFR.I have had similar problems under load where the motor would stumble with nothing to do with the electonics. Just thinking about pressure for example...The exhaust pressure is roughly equal to the intake, if things are matched. Once the pressure was high enough, conditions were just right and the motor would stumble. The exhaust valves were sticking open. Bigger springs....As pressure goes up, it puts a strain on the ignition parts. No surprise. You can see how it arched under the boot and etched the side of the plug. To combat this, the gap had to be closed down.Fuel type and amount of fuel ... is another fun one. As the pressures go up, this adds to the fun...Shown is another test jig to evaluate wideband sensors.

author: floobydust
author_rank: Super Contributor
timestamp: January 04, 2019, 05:35:00 pm
content: The coil primary waveform is also very useful, it's how modern ECU's do real-time misfire and ignition fault detection.Electronic ignition clamps the primary voltage to just under 400V, so max. output voltage is limited compared to points.There's two grounds in a car. One high-current ground is from engine block to battery, and the second smaller ground is from the engine block or battery to the car body/chassis. This is for the in-car loads like fuel pump, ignition, lights etc. A common mistake is forgetting the car body ground which the ignition module may not have been grounded to the block. The firewall is no good unless you have the ground strap from block to body. You can't rely on current flow through motor mounts and U-joints etc.Flipping the carb around, it would mean poor mixing in the intake manifold? I don't see a single carb used on the Holden hi-perf mods.If possible you can fit an O2 sensor and see each cylinder firing lean/rich to check balance. Maybe joe has tried this.Otherwise you'll blame the ignition system when nothing is wrong with it.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 04, 2019, 07:28:55 pm
content: Quote from: floobydust on January 04, 2019, 05:35:00 pmYes, I understand that. When we do receive the portable scope I have coming, we can check the primary.QuoteI insisted that they fit another ground wire from the back of the block to the firewall. Unfortunately, that made no difference to the fault.QuoteYes, that is what we conclude. This engine was first fitted with triple SU carburettors.They were removed and changed in one of the many attempts at eliminating this fault.QuoteThat would be good. I will see if they can oganise one.I should add that when they (the owner and his brother) tested the car on the track last weekend, they reported that it was cross firing. That is, it was backfiring out the exhaust every now and then. That suggests to me a major distributor problem.This engine is running on Methanol currently. Several fuels have been run in it previously.

author: Johnny10
author_rank: Frequent Contributor
timestamp: January 04, 2019, 07:58:47 pm
content: https://www.ebay.com/itm/US-POST-HANTEK-HT25-High-Voltage-OscilloScope-Secondary-Ignition-Automotiv-Probe/302674748580?epid=1061469482&hash=item4678d224a4:g:aHwAAOSwLg5bWELG:rk:1:pf:0Why improvise?

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 04, 2019, 08:54:28 pm
content: Quote from: Johnny10 on January 04, 2019, 07:58:47 pmThat is just what I was thinking while looking for Coax cable. Good point!Thanks.

author: Johnny10
author_rank: Frequent Contributor
timestamp: January 04, 2019, 09:40:27 pm
content: Which scope did you buy?I started with the Rigol 1054ZWorked well because I could roll back the display while learning to find the signals.A Picoscope or a Fluke 199 oscilloscope would work.The picoscope will come with automotive software for free.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 04, 2019, 10:31:02 pm
content: Quote from: Johnny10 on January 04, 2019, 09:40:27 pmI ordered this little one for my low voltage radio control model aircraft application - before I got involved in assisting the owner of the problem stock car and his brother who is also assisting. This has been highly recommended for my uses:https://www.banggood.com/Original-JYE-Tech-Assembled-DSO-SHELL-DSO150-Digital-Oscilloscope-Module-9V-p-1211151.html?rmmds=myorder&cur_warehouse=CNI am beginning to realise it will be useless for automotive high tension application. Also, could damage it first time used as such.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 05, 2019, 12:09:27 am
content: Quote from: floobydust on January 04, 2019, 05:35:00 pmAssuming narrow band, I have not used. The Bosch wideband sensor is slow. 100ms or so.Graphs below show about 1.3 seconds of data. You can see the wideband in the purple trace. The transmission is an auto for 1-2 but requires kill for the other shifts. There is a lot of air and unburned fuel pumping through the motor for that 30ms or so. You can see the wideband does pick it up but its no where near fast enough to see cylinder by cylinder.Second graph shows about a minute of data with the engine sitting without a load. The engine can build a fair bit of pressure on the 2-step. Once off the 2-step, it will tag the upper limiter. Both events can be seen with the wideband.

author: tautech
author_rank: Super Contributor
timestamp: January 05, 2019, 12:46:27 am
content: Ah, the two step.Boom, bang, boom.All hell breaks loose.Buddies 20B on Meth with 40lb of boost is something that is heard for miles !Oh yes Joe, I left EGT off the list.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 05, 2019, 09:27:34 pm
content: I will be driving up to where the car is (two hours away from here) today to assist one of the brothers work on it further.My suggestion to throw away the silicone plug leads and replace with copper was met with some ambivalence. (I am puzzled by this!)I don't want to get too insistent; I am only an onlooker/assistant and not a mechanic.I might have more to report tonight.Jim.

author: mikerj
author_rank: Super Contributor
timestamp: January 05, 2019, 10:05:59 pm
content: Quote from: Jim-0000 on January 05, 2019, 09:27:34 pmSilicone only refers to the insulation, it's possible to have copper cored HT leads with silicone insulation. It's the carbon string based cores leads that can break down over time.

author: Gregg
author_rank: Super Contributor
timestamp: January 06, 2019, 05:23:48 am
content: Don’t underestimate possible mechanical problems causing what seems to be an ignition problem. Things like weak valve springs, worn cam lobes, worn rocker shafts, worn or sticking lifters, worn valve guides, sticking valves, timing chain or belt tension / harmonics, worn distributor drive or partially blocked cooling passages to the cylinder head(s).Under load problems are often problems that simply are not noticed under light or no load. For instance the crankcase pressure is much higher under load because of increased blow by and if an intake valve is loose in its guide the mixture to that cylinder can be leaner. Under load exhaust valves get very hot and can grow considerably longer and if the clearance isn’t adequate, the exhaust valve can be held open too long.You stated that it is carbureted; it may be that the power valve isn’t functioning properly making it lean under load; a lean mixture can seem like an ignition problem partly because a lean mix is harder to ignite. A vacuum gauge may help here, a lot of old timers (like myself) swear by them for carbureted engine diagnosis in certain cases.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: January 06, 2019, 06:04:47 pm
content: Sight unseen is not a good position to do troubleshooting for an engine, however, there are a multitude of causes of an intermittent miss on a cylinder. Theses problems could be of either electrical or mechanical issues. Here are only a few that could be checked fairly easily.1. Check the plug or plugs in question for arc tracks, especially if they have a boot type spark plug wire.2. If this is a carburated engine, is that cylinder starved at higher RPMs due to a vortex in the air flow, i.e. in the intake?3. As mentioned earlier, valve float at high RPMs due to weak springs.4. Is the cam new or is the cam lobe worn on that cylinder more than on others? Is that lobe higher than others, was this checked out before installing?5. The distributor parts turn and this can cause runout at higher RPMs if the rotor bearing is worn, which can cause misfires.6. The rotor itself can move up or down if rotor is worn, causing collisions on distributor cap.7. The distributor cap can have cracks or problems seating on the rotor, yes, even if they are new, which can cause problems with firing.8. The plug wires could be the wrong type for the distro/plugs causing unmatched firing characteristics.9. If a condensor is used on the distro, it could be causing this behavior.10. The spark plug itself could be the problem, try a different brand or type.As far as checking the firing for this cylinder, a current probe around the primary of the coil would work at low voltages and when a misfire occurs, the shape of the pulse can tell you a lot about what the problem might be. The voltage on that pulse will rise if there was no spark due to an open and will fall if there was a short. You can use a portable scope or one of the modern automotive computers with a scope on it to do this, such as the Autel or OTC, or a portable o'scope such as the µScope, using a current probe.There are many more reasons that this could happen, hope this helps...

author: joeqsmith
author_rank: Super Contributor
timestamp: January 06, 2019, 07:35:24 pm
content: Quote from: tautech on January 05, 2019, 12:46:27 amMine are pretty tame. My street bike is injected and the low speed limiter on it is so smooth you hardly notice it.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 06, 2019, 09:14:39 pm
content: Quote from: tpowell1830 on January 06, 2019, 06:04:47 pmThanks for the reply.I would like some more details of these scopes. Can you provide full names and any links please?We are considering purchasing one specially for working on the two cars owned by the brothers. I will order one of the auto probes from Aliexpress linked to somewhere in a post above.Jim.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: January 06, 2019, 09:49:45 pm
content: Quote from: Jim-0000 on January 06, 2019, 09:14:39 pmI will do you one better and give you a link to an awesome mechanic who uses these tools and the µScope for troubleshooting, link in comments for scope.Hope this helps...

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 08, 2019, 12:18:39 pm
content: After another long day working on the problematic Holden grey motor (circa 1950,s), the two brothers, one of whom owns the vehicle have reluctantly agreed to change the plug leads over to solid cored ones. I first mentioned this many weeks ago. Their first response was: "we don't like copper cored leads"!New spiral wound, stainless cored leads have been ordered on ebay and we will await delivery. (It appears that copper cored leads are no longer available) Local suppliers could not get them, which seems astonishing to me! The also ordered some Platinum spark plugs.Meanwhile, I found out that a fellow member of the local Mens Sheddoeshave an oscilloscope along with two suitable probes for ignition analysis.If the new plugs and leads does not fix the miss fire, we will be borrowing that and using it on the engine. I will ask the owner of the scope to come out and assist, as he is an electronics engineer.So, we will have to find the problem some day soon, I figure.

author: Edison
author_rank: Frequent Contributor
timestamp: January 08, 2019, 02:19:07 pm
content: Quote from: Jim-0000 on January 08, 2019, 12:18:39 pmIs the fault really in the electricity?Our racing car was a faulty fuel pump - idling OK, irregular running under load, random performance drop - replacing the fuel filter = improvements, replacement of pump = fault has been rectified

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 08, 2019, 10:15:05 pm
content: Quote from: Edison on January 08, 2019, 02:19:07 pmI am not at all sure and will not be until and if we put an oscilloscope on the engine plug leads etc.However, we think it is the electrical system. The observed behavior that supports this is:1. The miss - fire is worst at idle and mid range steady RPM2. When revved up hard, it disappears, or almost does so.My assumption is if the problem was lack of fuel, the above would be opposite.The two mechanics assure me that there is plenty of fuel pressure. I have asked that question enough times to exhaust their patience.Thanks for the tip though.There is a fuel pressure gauge somewhere on the car I think? I will look next time we are working on the car. Will not be doing so for a week or so. It is here next door to me, but all covered up with tarps etc.

author: Edison
author_rank: Frequent Contributor
timestamp: January 08, 2019, 10:52:28 pm
content: Checking the ignition is the first!Minus control - battery / chassis - chassis / engineIs the injection system fully electronic?Do you have? speed sensor, engine vibration sensor, air weight, lambda .....Is the carburettor or ecotronic system?Hall probe in distributor, burned distributor cap, reading in chambers (diaphragms, hoses, pressure sensors) jets, float, leaky chambers ........there's a lot of it

author: Edison
author_rank: Frequent Contributor
timestamp: January 08, 2019, 10:59:32 pm
content: little out of far awayI would have stopped

author: tautech
author_rank: Super Contributor
timestamp: January 08, 2019, 11:16:53 pm
content: Quote from: Jim-0000 on January 08, 2019, 10:15:05 pmCheck all the A/R system.....hoses, fittings, points plate free, flyweights and springs OK and sometimes old dizzy shafts need rebushing so that points gaps and dwell angles remain consistent throughout the rev range.

author: maginnovision
author_rank: Super Contributor
timestamp: January 08, 2019, 11:25:09 pm
content: Two 'career mechanics' should not need so long to figure something like this out. Especially when you consider the symptoms stayed when the ignition components were swapped. I'd recommend taking it elsewhere no matter what the actual issue ends up being.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 09, 2019, 03:18:33 am
content: Quote from: maginnovision on January 08, 2019, 11:25:09 pmI could not agree more!QuoteAlso, the missfire was there with the first (or original) engine in the car when it was first acquired. So, much more than ignition components have been swapped. I might have already mentioned this, but the triple 11/2 SU carbs were swapped for a single (forgot the brand) carb and a new manifold fabricated out of two, all in an attempt to fix this miss fire.The engine was swapped as this one was being modified extensively for performance and the original one was being used meanwhile.QuoteYou have lost me here. If the "actual issue" is found, there will be no need to take it "elsewhere"?

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 09, 2019, 03:35:02 am
content: Quote from: Edison on January 08, 2019, 10:52:28 pmThe ignition system has been jumpered wtih a separate battery and jumper leads, all independent from the cars wiring. Same result.QuoteNo injection system. Please read other posts - naturally aspirated. Two carb systems tried. Same result.Quote

author: maginnovision
author_rank: Super Contributor
timestamp: January 09, 2019, 05:08:53 am
content: Quote from: Jim-0000 on January 09, 2019, 03:18:33 amWhat I mean by the last bit is that even if the actual issue(misfire is a symptom) has/had anything to do with the ignition system it still would be/would've been the right thing to take it elsewhere. Unless of course you don't mind the time lost and the work is very cheap.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 09, 2019, 09:43:49 am
content: QuoteI would not have a clue where "elsewhere" would be to take it, even it if was mine!

author: Johnny10
author_rank: Frequent Contributor
timestamp: January 09, 2019, 01:43:19 pm
content: If you are helping to solve the engine mystery than you should have something to bring to the table.An engine misfire is a symptom of a problem with Fuel, Spark or Compression.You seem to have fixed your sites on Spark, yet after completely changing the ignition system you still have misfire.This is a distributor type ignition, besides the electricity flowing to the spark plugs there are also mechanical issues to be addressed.I hadn't realized that this Grey Motor has cult status in the Australian Racing world.You should be able to find lots of information about every aspect of this engine.Actually in the short time I researched the engine I found tons of information.This engine was tuned for performance over quite a number of years.I enjoyed acquiring the knowledge and collecting and building all the tools to know what was really happening in my engine.I was never much for parts changing as a repair technique.You are on an adventure, good luck, get in there get your hands dirty.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 09, 2019, 06:00:38 pm
content: Quote from: Jim-0000 on January 09, 2019, 03:18:33 amWould be funny if the fuel pump or the cell was the problem. Maybe all their high load testing is at the track instead of on the dyno and there's no baffles in the cell. Maybe they are pumping air... Maybe the pickup in the cell doesn't stay where the fuel is...I had similar problems with oil. It tough to keep fluids where you want them. After several baffle and pickup designs I sorted it out.... With data logging... (Add fuel pressure to that list as well)

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 09, 2019, 08:39:43 pm
content: Quote from: joeqsmith on January 09, 2019, 06:00:38 pmWhat is the "cell"? Is that what we would call the tank? I assume it is. This car is fitted with a tank designed specially for racing.The car has been on the dyno twice. The same symptoms occur there as on the track.I don't know how fuel flow is, or could be, data logged.Thanks for the post.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 09, 2019, 08:47:34 pm
content: Quote from: Johnny10 on January 09, 2019, 01:43:19 pmI mentioned in an earlier post that I have been suggesting that solid core plug wires should be fitted to replace the common type suppression leads on the car (core type unknown), for some weeks now. There has been resistance and all of it is not in the car! (pun intended).Somewhat reluctantly, the owners have ordered a set of solid cored ones as described above.Also, I now have arranged the loan of an oscilloscope and suitable probes with which to do an ignition analysis should the new leads not solve the problem.I don't have anything else to "bring to the table".Meanwhile, the owners brother is talking about the problem still being induction related. Even though two very different carburettors and manifolds have been fitted and tried.But for all I know, he may be on the right track as I am out of my experience and skill range here.QuoteNot quite. See above.Thanks for your encouragement.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 09, 2019, 11:39:41 pm
content: Quote from: Jim-0000 on January 09, 2019, 08:39:43 pmYes, the tank that holds the fuel.https://www.onallcylinders.com/2013/03/25/monday-mailbag-fuel-cells-vs-fuel-tanks/To record the pressure I just put a sensor right in the fuel distribution block.

author: dardosordi
author_rank: Regular Contributor
timestamp: January 11, 2019, 09:51:52 am
content: Hi, I had a similar issue in my Ford EcoSport. The mechanic replaced sparkplugs, leads, carburetor an the failure persisted. I scoped it, used OBD scanner and could not figure it out.The mechanic suggested changing the oil the manufacturer recommended for a thicker one. All fixed.

author: Edison
author_rank: Frequent Contributor
timestamp: January 11, 2019, 09:48:12 pm
content: Quote from: dardosordi on January 11, 2019, 09:51:52 amFord ekosport had so-called hydroshells to control the clearance of the valves - there was an absolute need for oil with a specific viscous number. Other oil = other dynamic pressure = malfunction hydra = changing valve clearance = irregular operation.

author: Gregg
author_rank: Super Contributor
timestamp: January 12, 2019, 04:45:18 am
content: Now that we know more about the engine being a vintage Holden Grey, we may be able to narrow things down a bit. As far as “taking it elsewhere” is concerned, that is hardly in the spirit of the EEV blog forum even if it turns out not electrically related.An intake manifold modified from the horrors of triple SU carbs to an unknown single carb is certainly suspect for vacuum leaks; which would fit the description of symptoms. Not that triple side draft carbs don’t have their advantages; multiple SUs need a lot of fiddling to tune properly and to keep in tune. Jaguar certainly liked multiple SUs and they ran quite well when in tune. Single carburetors on inline sixes have always had issues with cylinders 1 and 6 getting a proper fuel mixture at all RPM and engine load conditions due to the longer runner length; generally this is overcome by running a richer mixture to the other cylinders to compensate.Next on my list of possibilities would be valve train problems. Rocker arm wear and misalignment are particularly hard to diagnose without taking it all apart. Are the lifters solid or hydraulic and matched to the cam profile? The oil pump and distributor are driven off of the back portion of the camshaft and wear, misalignment or loose timing chain are possibilities.Another possibility, although remote, is head gasket sealing; the head stud layout in the Holden isn’t optimal for keeping a good head gasket seal in performance engines.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 12, 2019, 09:41:06 pm
content: Quote from: Gregg on January 12, 2019, 04:45:18 amI am glad you agree!QuoteThe carburettor is a Holley. The intake manifold was fabricated from two manifolds to suit the carb and the head. It was professionally welded and machined flat etc. New gasket fitted. Zero chance of leak, all who have looked at it agree.QuoteBrand new roller rocker gear is fitted (at great expense!). Problem here? Most unlikely I suspect.QuoteI don't know. I would assume the lifter are solid, but not at all sure. I will find out later this week.QuoteCooling system pressure test has been done a couple of times. The head stud layout tip is one worth some consideration.Current prospects and plan:1. Fit solid core ignition leads (plug leads) when they arrive in the mail.2. If problem persists, do a full oscilloscope investigation of the ignition system. Now we have the equipment available.Thanks for the posting.

author: vk6zgo
author_rank: Super Contributor
timestamp: January 13, 2019, 12:59:58 am
content: Quote from: Jim-0000 on January 12, 2019, 09:41:06 pmIf it is a grey motor it will almost certainly have solid lifters.The modifications necessary to fit hydraulic lifters would be so profound that most people would just ditch the "grey" & go for a "red" motor.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 13, 2019, 02:31:24 am
content: If it is a grey motor it will almost certainly have solid lifters.The modifications necessary to fit hydraulic lifters would be so profound that most people would just ditch the "grey" & go for a "red" motor.Yes.Thanks for the post.

author: floobydust
author_rank: Super Contributor
timestamp: January 13, 2019, 04:54:42 am
content: If there is a vacuum port right at the carburetor, you can connect a MAP sensor + scope and observe the vacuum dips for each cylinder, what the carb sees. Or add a port to the intake manifold.I'm thinking about the intake manifold volume and uneven pulsating flow because the runners are different lengths - some carbs freak out if the vacuum-ripple is great.

author: Circlotron
author_rank: Super Contributor
timestamp: January 13, 2019, 06:32:48 am
content: Posting so I get updates.

author: Edison
author_rank: Frequent Contributor
timestamp: January 13, 2019, 11:43:44 am
content: Quote from: floobydust on January 13, 2019, 04:54:42 amThis is the principle management Ecotronic, in my case, the sensors were four - the vacuum was compared in different chambers (the Weber double carburetor).Your carburettor is not equipped with an electric needle choke?

author: Gregg
author_rank: Super Contributor
timestamp: January 14, 2019, 03:17:02 am
content: 1948 Chev pickupQuote from: floobydust on January 13, 2019, 04:54:42 amFloobydust: that is an interesting electronic troubleshooting method for a mechanical problemAnother troubleshooting method, more old school, is to pull or short the plug wires one at a time when the engine is running rough to see which cylinder(s) are least affected by no firing. This may narrow down the search.Knowing the model of Holley carb may help us; each carb has its own quirks. Is this the Holley 32/36 copy of the Weber design?The vacuum leak test is still a good idea. At low idle, lean out the carburetor as much as you can and still have it running and spray some flammable carb cleaner at all gasketed intake areas and at all welded areas to see if the RPM rises. You can test your setup by squirting a tiny amount into the carb intake and noting the result.Two weeks ago I was helping a friend with a with a 1948 Chev pickup with a single throat Carter “rebuilt” carb and it was having similar symptoms. Installing the idle jet and emulsion tube assembly from the original carb solved the problem.

author: vk6zgo
author_rank: Super Contributor
timestamp: January 14, 2019, 03:38:49 am
content: My Holden EH's Stromberg carby back in the day, was inadvertently fitted with the main jet from the grey motor.All worked OK, except that every now & then, the thing would hesitate, & sometimes stall.I got a carby overhaul kit from the Auto section of my old work, & they asked :- "Do you want the full kit?"The difference was that kit had a correct replacement jet---- sneaky way of avoiding a recall!Fitted it, & no more problems.Holden had a bit of a "glitch" around that time--- someone decided the "grey motor" clutch was adequate for an engine with 30% more power.Sometimes it was, but mine kept killing clutch plates.(granny-v-revhead?)I ended up fitting the clutch assembly for the higher power "179cu in" option.

author: floobydust
author_rank: Super Contributor
timestamp: January 14, 2019, 05:43:26 am
content: To find vacuum leaks, I use propane. Take a blow torch or BBQ tank (after low pressure regulator) and a long hose, 1/4" tubing with a metal wand and move that around the seams. Enough propane to supply say a candelabra, just a little flow.You can easily find leaks, the RPM's jump right up. Test it by holding the wand at the carb inlet, letting propane in and see the tach jump up.

author: maginnovision
author_rank: Super Contributor
timestamp: January 14, 2019, 05:48:34 am
content: Quote from: floobydust on January 14, 2019, 05:43:26 amI've always used carb cleaner, like Gregg. It's usually much more handy for me than propane.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 14, 2019, 09:31:05 pm
content: Thanks for the good replies.The carburettor cleaner tip for chasing vacuum leaks is a good one. However, it is not applicable in this case.We are still waiting for the new plug leads. I expect them one day this week.There will be no work on the Holden until they arrive and we try them.

author: Jim-0000
author_rank: Regular Contributor
timestamp: January 15, 2019, 10:20:20 pm
content: Just to clarify; the owner and brother are sticking to just changing one thing at a time and then testing it before trying something else. For obvious reasons; they dearly want to know what is the reason for this problem.Seems logical to me, so I am not arguing.

author: Jim0000
author_rank: Contributor
timestamp: March 11, 2019, 10:11:49 am
content: I am just posting to say I have no positive news to report about this engine problem.In fact, the problems have just compounded along the way. The second camshaft is starting to fail in this engine. They are loosing lobes gradually for no apparent reason, thereby making the tappets increasingly noisy and filling the oil with fine, case hardening steel fragments.The lifters were re-faced each time.The owners (and me) are all stumped!

author: Jim-0000
author_rank: Regular Contributor
timestamp: March 25, 2019, 11:18:53 pm
content: Both problems have been identified and fixed on this engine.The miss-fire was caused by an induction problem. The carb was rotated (again) this time @ 90 deg. And the engine ran smoothly. The owners brother has being saying for some time that this was the problem, and it turned out he was correct.The problem of the camshaft lobes failing (wearing away very rapidly with all sorts of problems resulting) was due to a mis-match of cam and cam followers.A ground standard Holden grey motor cam shaft was fitted, but Falcon cam followers were used.Holden and Falcon use a different method to rotate the followers:1. Holden have the followers slightly off centre with relation to the cam lobes.2. While, Falcon have a very slightly concave top and the cam lobes are ground with a slight taper - in the direction of the axis of the shaft.The fix was to grind the shaft again, and re-face the followers flat.At least, I think that is what they did. I will ask again next time I see one of the brothers who have been working on this.Of course, the engine had to be flushed out as good as possible and the filters changed. There would be metal fragments in the oil!............

author: Circlotron
author_rank: Super Contributor
timestamp: March 26, 2019, 12:29:17 am
content: Though it was first used in 1948, the Holden grey motor is basically a 1920's design. That's not to disparage this old timey donk - quite the opposite. It's surprising just how much technology and hidden engineering detail went into these old things, while being superficially dirt simple, made it something that suitably maintained would run reliably for decades.

author: Jim-0000
author_rank: Regular Contributor
timestamp: March 26, 2019, 02:51:04 am
content: Yes I agree.The only thing that I don't like about it, along with the later Red Holden motor, is the rope main bearing seal!From memory, the owners modified it to take a two part modern silicone seal.I know they did that on the turbo charged mark 3 Zephyr they are running in another car.

author: Circlotron
author_rank: Super Contributor
timestamp: March 26, 2019, 04:58:26 am
content: Don't forget shared inlet ports, and on the grey, shared exhaust as well.Fibre cam gear.And the red motor has the fan belt in a groove around the perimeter of the harmonic balancer! For it to do it's job properly there should be nothing touching it. Sounds like a bean counter overruled an engineer on that one...

author: tautech
author_rank: Super Contributor
timestamp: March 26, 2019, 06:18:59 am
content: Quote from: Circlotron on March 26, 2019, 04:58:26 amYep, they were still running fibre in the last of the 202's, the later black version in the Commodore before Holden went to the even fire over-bored ex Buick V6.

author: Jim-0000
author_rank: Regular Contributor
timestamp: April 13, 2019, 11:20:54 pm
content: The stock car that this motor is in will be raced in two weeks. All prepared and ready.So, this will be the first proper test to see if the problem has been totally resolved. Just from running the engine with the car stationary, it sure appears to be so.Thanks to all contributors. It has been an informative and interesting experience all told!Jim.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 13, 2019, 11:46:58 pm
content: Good to hear their getting it sorted. Keep us posted on how it runs.