From: jbm@eos.arc.nasa.gov (Jeffrey Mulligan)
Subject: Re: Nissan Pulsar/Carb. Problem
Organization: NASA Ames Research Center
Distribution: usa
Date: Wed, 16 Sep 1992 01:38:13 GMT

srv@philabs.philips.com (Sreeraman Venkitasubrahmanian) writes:


>I have a 1983 Nissan Pulsar NX (1.6 l, 4cyl, Carb. Inj.) with the following
>problem. At first the car used to die out on idle (at stop lights etc.). 
>It would start back and run fine until the next stop. I did not seriously
>bother with it then (about 2 weeks back). 

>Few days back it started stalling badly while driving. When I stopped the
>car and started again it ran fine. This problem occured a few times again.
>When this stalling occured the car moved in jumps as if I had pumped and
>released the accelarator in spurts. Yesterday I barely managed to drive
>back home from work (2 miles).

>Today morning I could not drive the car at all. It would start and immed.
>die out. Pressing the accelerator had no effect. I could rev it up by 
>pumping the accel continuously.  But as soon as I stopped this, it died 
>out. 

I have had two fuel related problems with some similarity to yours.
The first was when a piece of crud got into the carb float bowl,
and intermittently blocked the main jet, cutting off fuel.
Pumping the accelerator pedal would allow the car to limp along,
since the accelerator pump provided an alternate route for fuel to
get to the intake.

The second time was just this spring.  I was on the freeway and lost power.
After pulling over, I was able to restart and drive 100 yards before
losing power again.  I thought I might be out of gas (broken gauge,
use note pad and odometer), so I abandoned the car, got to a phone
and had a friend come by.  After dumping in a few gallons, the car
started up, drove half a mile and then died again.  Well, at least
I got it parked in a parking lot for the night.

The next day I came back, verified the fuel pump was sending
fuel to the carb, checked other stuff, changed the fuel filter.
Started it up, drove around, after a few minutes it died again.
This time when I looked into the carb barrel while working the
throttle linkage, the streams from the accel. pump quickly died
out - the fuel bowl was empty!  To make a long story short, the
gas cap had failed.  yes, the gas cap.  It was supposed to be vented,
the rubber gasket ring had deteriorated and was blocking the vent.
As fuel was pumped from the tank, vacuum built up until the pump
couldn't suck any fuel.  Letting the car sit a while relieved this
condition.

>I had the car towed to a repair shop. The mechanic says it is a carburettor
>problem and replacement would cost $300-$400. He said that he could make it 
>run a little better by advancing the ignition timing to the max. 

>After this adjustment the car idles fine. I can also rev the engine by
>pressing the accel. It also drives fine for a short while after starting.
>After that the same stalling comes back. At idle the engine rpm sometimes
>seems to lag the accel for a second or so. This lag is very pronounced
>while driving and moves the car in jumps.

The lag would be consistent with no gas in the accelerator pump,
possibly caused by low fuel level in the float bowl.

>I'm not so sure that it's a carb. problem since it runs fine for a 
>short time after starting. Also advancing the timing seems to have helped
>at least on idle.

The bit about running fine for a short time after startup
reminded me of my gas cap problem.

>Now for your advice:

>Is this really a carb. problem? If so can I fix it without having to 
>replace the whole carb.? 

I don't see why the ignition timing should have anything to
do with a fuel problem (if it is a fuel problem).  Is it possible
that the mechanic is bullshitting you?

>I would like to fix the car myself. Any suggestion from you folks will
>be of help.

Find out if you have a vented gas cap.  Take it off and look at it.
Try running the car for a short while without it.  This is a long
shot, but it's easy and costs nothing.

Let us know how this turns out.

Good luck!
Jeff

-- 

	Jeff Mulligan (jbm@eos.arc.nasa.gov)
	NASA/Ames Research Ctr., Mail Stop 262-2, Moffett Field CA, 94035
	(415) 604-3745