Integrated fuel primer and crankcase drain system for internal combustion engine

An internal combustion engine comprises a combustion chamber and a crankcase which extends from the combustion chamber. A primary fuel delivery system introduces fuel from a fuel source into the combustion chamber, and a primer fuel delivery system is selectively operable for introducing fuel from the source into the combustion chamber in addition to fuel which is introduced by the primary fuel delivery system. A collector assembly communicates with the crankcase for accumulating residual fuel from the crankcase, and a residual fuel delivery system supplies fuel from the collector assembly into the combustion chamber. A control valve mechanism is connected to the primer fuel delivery system and the residual fuel delivery system for blocking the supply of fuel by the residual fuel delivery system during operation of the primer fuel delivery system.

BACKGROUND OF THE INVENTION 
I. Field of the Invention 
The invention relates to internal combustion engines and, more 
particularly, to fuel primers and crankcase drain systems for internal 
combustion engines. 
II. Description of the Prior Art 
Fuel primer systems for internal combustion engines are known and disclosed 
in the following U.S. Pat. Nos.: 
______________________________________ 
Parker 2,287,900 June 30, 1942 
Casteel 2,553,079 May 15, 1951 
Roosa 2,821,183 January 28, 1958 
Gastinne 3,548,796 December 22, 1970 
Schlagmuller 
et al 3,614,945 October 26, 1971 
Rachel 3,646,915 March 7, 1972 
Nagy et al 3,646,918 March 7, 1972 
Aono 3,704,702 December 5, 1972 
Porsche et al 
3,799,138 March 26, 1974 
Mondt 3,888,223 June 10, 1975 
______________________________________ 
A crankcase drain system for an internal combustion engine is disclosed in 
U.S. Pat. No. 3,376,380 issued to Schultz on Oct. 2, 1973. 
None of the above prior art discloses a means for integrating a fuel primer 
system with a crankcase drain system for an internal combustion engine. 
SUMMARY OF THE INVENTION 
The invention provides an engine comprising a combustion chamber and a 
crankcase which extends from the combustion chamber. First fuel delivery 
means communicates with the combustion chamber and is adapted for 
connection to a fuel source, the first fuel delivery means being thereby 
operative for introducing fuel from the fuel source into the combustion 
chamber. Second fuel delivery means also communicates with the combustion 
chamber and is adapted for connection to a fuel source, the second fuel 
delivery means being thereby operative for introducing fuel into the 
combustion chamber in addition to the fuel introduced by the first fuel 
delivery means. First control means is connected to the second fuel 
delivery means for selectively operating the second fuel delivery means to 
introduce fuel into the combustion chamber. Collector means communicates 
with the crankcase for accumulating residual fuel from the crankcase, and 
third fuel delivery means communicates with the collector means and the 
combustion chamber for supplying residual fuel from the collector means 
into the combustion chamber. Second control means is connected to the 
second fuel delivery means and the third fuel delivery means for blocking 
the supply of residual fuel by the third fuel delivery means during 
operation of the second fuel delivery means to introduce fuel into the 
combustion chamber. 
In accordance with one embodiment of the invention, the first fuel delivery 
means includes first fuel conduit means for conducting fuel from the fuel 
source to the combustion chamber, and first fuel pumping means which 
communicates withh the first fuel conduit means for pumping fuel through 
the first fuel conduit means from the fuel source into the combustion 
chamber. In this embodiment, the second fuel delivery means includes 
second fuel conduit means which communicates with the first fuel pumping 
means and the combustion chamber and which conducts fuel from the first 
fuel pumping means into the combustion chamber subject to the operation of 
the first control means. 
In accordance with one embodiment, the first control means includes first 
valve means which communicates with the second fuel conduit means and 
which is operatively movable between a closed position for interrupting 
the conduction of fuel from the first fuel pumping means into the 
combustion chamber and an open position for permitting the conduction of 
fuel from the first fuel pumping means into the combustion chamber. In 
this embodiment, the first valve means is biased toward the closed 
position, and activating means is provided for moving the first valve 
means against the action of the biasing means from the closed position to 
the open position. 
In accordance with one embodiment, the activating means includes an 
electrically actuated solenoid, as well as manual means for moving the 
first valve means from the closed position to the open position against 
the action of the biasing force. 
In accordance with one embodiment, the third fuel delivery means includes 
third fuel conduit means for conducting fuel from the collector means to 
the combustion chamber, and second fuel pumping means for pumping fuel 
through the third fuel conduit means from the collector means into the 
combustion chamber in response to pulsating pressure. In this embodiment, 
the engine further includes a piston which is mounted for reciprocative 
movement within the combustion chamber, and the crankcase forms the source 
of pulsating pressure in response to the reciprocative movement of the 
piston. 
In accordance with one embodiment, the second fuel conduit means includes a 
first fuel supply passage having an inlet end communicating with the first 
fuel pumping means and an outlet end communicating with the combustion 
chamber. The third conduit means includes a second fuel supply passage 
having an inlet end communicating with the collector means and an outlet 
end communicating with the first fuel supply passage. In this embodiment, 
the second control means includes second valve means operatively movable 
between an open position affording communication between the inlet end of 
the second fuel supply passage and the first fuel supply passage in 
response to the flow of fuel in the second fuel supply passage subject to 
a magnitude of pressure and a closed position blocking the communication 
between the inlet end of the second fuel supply passage and the first fuel 
supply passage in response to the flow of fuel in the first supply passage 
subject to a magnitude of pressure which exceeds the magnitude of fluid 
pressure in the second fuel supply passage. 
In accordance with one embodiment, the second control means includes means 
for biasing the second valve means toward the closed position, and, in 
this embodiment, the biasing means works in combination with the fluid 
pressure in the first fuel supply passage for closing the second valve 
means. 
In accordance with one embodiment, the second fuel delivery means includes 
third valve means communicating with the first fuel supply passage 
intermediate the outlet end of the second fuel passage and the inlet end 
of the first fuel supply passage and operative for preventing the flow of 
fuel in the first fuel supply passage toward the inlet end of the first 
fuel supply passage while permitting the flow of fuel in the first fuel 
supply passage toward the outlet end thereof. 
In accordance with one embodiment, the combustion chamber includes a 
sidewall having an inlet port passing therethrough, and the second fuel 
delivery means includes nozzle means communicating with the inlet port for 
introducing fuel into the combustion chamber through the inlet port during 
operation of the second fuel delivery means. 
In accordance with one embodiment, the engine further includes a second 
combustion chamber in addition to the first mentioned combustion chamber, 
and a second crankcase in addition to the first mentioned crankcase. In 
this embodiment, the first fuel delivery means is operative for 
introducing fuel into both the first and second combustion chambers, and 
the second fuel delivery means is likewise operative for introducing 
additional fuel into both the first and second combustion chambers, 
subject to the operation of the first control means. Also in this 
embodiment, the collector means includes a first collector means 
communicating with the first crankcase for accumulating residual fuel from 
the first crankcase, and second collector means communicating with the 
second crankcase for accumulating residual fuel from the second crankcase. 
The third fuel delivery means includes first drain conduit means for 
supplying residual fuel from the first collector means to the second 
combustion chamber, and second drain conduit means for supplying residual 
fuel from the second collector means to the first combustion chamber. In 
this embodiment, the second control means includes means for 
simultaneously blocking the supply of residual fuel by the first drain 
conduit means and the second drain conduit means during operation of the 
second fuel delivery means. 
One of the principal features of the invention is the provision of an 
engine having a fuel primer system which is integrally connected with a 
crankcase fuel drainage system, thereby reducing the overall complexity of 
engine construction. 
Another of the principal features of the invention is the provision of the 
engine having integrally connected fuel primer and drainage systems and 
which includes control means for blocking the return of residual fuel 
through the drainage system during operation of the primer system. 
Other features and advantages of the embodiments of the invention will 
become apparent upon reviewing the following general description, the 
drawings and the appended claims.

Before explaining the embodiments of the invention in detail, it is to be 
understood that the invention is not limited in its application to the 
details of construction and the arrangement of components set forth in the 
following description or illustrated in the drawings. The invention is 
capable of other embodiments and of being practiced and carried out in 
various ways. Also, it is to be understood that the phraseology and 
terminology employed herein is for the purpose of description and should 
not be regarded as limiting. 
GENERAL DESCRIPTION 
Shown in FIG. 1 is an internal combustion engine 10 which embodies various 
of the features of the invention. Generally, the engine 10 includes a 
combustion chamber 12 and associated first, second and third fuel delivery 
means, respectively 14, 16, and 18, which introduce fuel into the 
combustion chamber 12 to sustain engine operation. 
While various engine constructions are possible, in the illustrated 
embodiment, a block member 22 includes a cylinder 24 which defines the 
combustion chamber 12. The block member 22 also includes a crankcase 26 
which extends from the cylinder 24. A piston 28 is mounted for 
reciprocative movement inside the cylinder 24, being connected by a 
connecting rod 30 to a crankshaft 32 which is rotatably mounted in the 
crankcase 26. A spark plug 34 or the like extends into the combustion 
chamber 12, and fuel which is introduced into the combustion chamber 12 by 
the first, second or third fuel delivery means 14, 16 or 18 is ignited by 
the spark plug 34, thereby causing reciprocative movement of the piston 28 
which in turn drives the crankshaft 32. 
The first fuel delivery means 14 includes first fuel conduit means 36 which 
is suitably connected to a source of fuel 20 and conducts fuel from the 
fuel source 20 to the combustion chamber 12. While various constructions 
are possible, in the illustrated embodiment, the first fuel conduit means 
36 includes a carburetor having an air induction passage 38 which directs 
air from the atmosphere into the crankcase 26, typically through a 
conventional reed valve assembly 40. A conduit 42 delivers fuel from the 
fuel source 20 into the air induction passage 38, and first fuel pumping 
means 44, such as an electrical fuel pump or the like, is provided for 
pumping fuel through the conduit 42. 
By virtue of this construction, an air-fuel mixture is formed in the air 
induction passage 38, being thereafter drawn through the reed valve 
assembly 40 and a suitable fuel induction port 57 into the combustion 
chamber 12 in response to pulsating pressure variations which occur in the 
crankcase 26 and which are occasioned by piston reciprocation. As should 
now be apparent, the first fuel delivery means 14 represents the primary 
fuel supply system for the engine 10. 
When the engine 10 is cold or has been inoperative for some time, it is 
often desirable to crank the engine 10, such as by a manually or 
electrically acutated starter mechanism (not shown), for an extended 
period of time in order that sufficient combustible quantity of fuel is 
delivered by the first fuel delivery means 14 to the combustion chamber 
12. To supplement the supply of combustible fuel which is introduced into 
the combustion chamber 12 during cranking operations, and to thereby 
facilitate starting of the engine 10, the second fuel delivery means 16 
introduces fuel into the combustion chamber 12 in addition to the fuel 
which is introduced by the first fuel delivery means 14. Associated first 
control means 46 is connected with the second fuel delivery means 16 so 
that the second fuel delivery means 16 can be selectively operated. As 
thus described, the second fuel delivery means 16 represents a fuel primer 
system for the engine 10. 
While various constructions are possible, in the illustrated embodiment, 
the second fuel delivery means 16 includes second fuel conduit means 48 
which communicates with the fuel pump 44 and the combustion chamber 12 and 
which conducts fuel from the fuel pump 44 into the combustion chamber 12, 
subject to the operation of the first control means 46. 
More particularly, a first conduit 50 has an inlet end 52 which is 
connected with the fuel pump 44 and has an outlet end 54 which is 
connected to a fuel metering orifice or nozzle 56. The nozzle 56 passes 
through an inlet port 58 formed in a sidewall of the block member 22 near 
the upper end of the fuel induction port 57, such that fuel emitted by the 
nozzle 56 enters the combustion chamber 12 in addition to the fuel which 
is introduced by the first fuel delivery means 14 and which is drawn by 
pulsating pressure through the fuel induction port 57. 
By virtue of this construction, fuel delivered by the second fuel delivery 
means 16 is emitted directly into the combustion chamber 12, and the 
requirement for a conventional choke valve assembly (not shown) in the air 
induction passage 38 is thereby eliminated. Likewise, the possibility of 
"over-choking" or flooding the engine 10 during priming is substantially 
reduced, inasmuch as any excess fuel emitted into the combustion chamber 
12 by the nozzle 56 will be quickly expelled from the combustion chamber 
12 through the exhaust port 60 by pulsating pressure occasioned by piston 
reciprocation during cranking. 
Referring now to FIG. 2, the first control means 46, which controls the 
conduction of fuel through the second fuel delivery means 16, takes the 
form of a primer fuel control valve assembly which is connected in line 
with the first conduit 50 between the fuel pump 44 and the nozzle 56. The 
control valve 46 is operatively movable between a closed position (shown 
in phantom lines in FIG. 2) for interrupting the flow of fuel to the 
nozzle 56 through the first conduit 50 and an open position (shown in 
solid lines in FIG. 2) for permitting the flow of fuel to the nozzle 56 
through the first conduit 50. 
In order that the control valve 46 may be selectively moved between the 
closed and open positions, in the illustrated embodiment (see FIG. 2), the 
control valve 46 is biased toward the closed position, such as by a spring 
62, and an electrically controlled solenoid 64 is operatively connected 
with the control valve 46 for moving the valve 46 from the closed position 
to the open position against the action of the biasing spring 62. The 
solenoid 64 is in turn operated by means of a conventional switch 66 which 
is accessible for operation by the engine operator. Thus, as the operator 
actuates the engine starter mechanism, the operator may simultaneously 
actuate the switch 66 to operate the second fuel delivery means 16 to 
prime the engine 10. 
As heretofore described, the fuel pump 44 and the control valve 46 are 
electrically actuated, typically by means of a battery (not shown). In 
order that the engine may be manually primed should electrical failure 
occur, a manually actuated fuel pump, such as a resilient "squeeze" bulb 
68 or the like (shown in phantom lines in FIG. 2), may be connected with 
the first conduit 50, and a manually actuated lever assembly 70 may be 
operatively connected with the control valve 46 so that the control valve 
46 may be manually opened against the action of the biasing spring 62. The 
squeeze bulb 68 and lever assembly 70 provide a secondary or back-up 
primer system should electrical failure occur. 
During normal operation of the engine 10, unignited fuel can collect in the 
crankcase 26 and cause the formation of erratic fuel-air ratios which 
interfere with efficient engine combustion. To return this residual fuel 
from the crankcase 26 to the combustion chamber 12, the engine 10 includes 
a crankcase drainage system. Generally, and referring to FIG. 1, collector 
means 72 communicates with the crankcase 26 for accumulating the residual 
fuel from the crankcase 26, and the third fuel delivery means 18 
communicates with the collector means 72 and with the combustion chamber 
12 to supply residual fuel from the collector means 72 into the combustion 
chamber 12. 
While various constructions are possible, in the illustrated embodiment (as 
best shown in FIG. 1), the collector means 72 includes an outlet port 74 
which is formed in a sidewall of the crankcase 26 in the vicinity of the 
reed valve assembly 40. A drain nipple 76 or the like communicates with 
the outlet port 74, and the third fuel delivery means 18 includes a second 
conduit 78 which communicates with the drain nipple 76 and with the 
combustion chamber 12. Second fuel pumping means 80 (shown in phantom 
lines in FIG. 1) pumps the residual fuel through the second conduit 78. 
While the second fuel pumping means 80 can be variously constructed and be, 
for example, a separate fuel pump which operates independently of the 
first mentioned fuel pump 44, in the illustrated embodiment, the pulsating 
pressure variations which occur in the crankcase 26 as a result of piston 
reciprocation serve to pump the residual fuel out of the crankcase 26 
through the second conduit 78 and into the combustion chamber 12. 
As shown in FIG. 1, the third fuel delivery means 18 intersects the second 
fuel delivery means 16 such that residual fuel, like the primer fuel, is 
emitted directly to the combustion chamber 12 through the heretofore 
described nozzle 56. In particular, the second conduit 78 has an inlet end 
82 which is connected with the drain nipple 76 and an outlet end 84 which 
intersects with the first conduit 50 intermediate the nozzle 56 and the 
primer fuel control solenoid valve 46. 
In order that the second fuel delivery means 16 and the third fuel delivery 
means 18 operate independently of each other and do not conduct fuel to 
the nozzle 56 at the same time, second control means 86 (shown 
diagrammatically in FIG. 1) is connected to the second and third fuel 
delivery means 16 and 18 near their point of intersection for blocking the 
supply of residual fuel by the third fuel delivery means 18 during 
operation of the second fuel delivery means 16. 
More particularly, in the embodiment shown in FIG. 3, the second control 
means includes a check valve 86 or the like which is connected in line 
with the second conduit 78 near its outlet end 84. The check valve 86 is 
operatively movable in response to fluid pressure between a closed 
position (shown in solid lines in FIG. 3) which blocks communication 
between the inlet end 82 and the outlet end 84 of the second conduit 78, 
and consequently blocks the flow of fuel therebetween, and an open 
position (shown in phantom lines in FIG. 3) which affords communication 
between the inlet end 82 and the outlet end 84 of the second conduit 78, 
and thereby permits the flow of fuel through the second conduit 78 to the 
nozzle 56. 
Since the flow of fuel through the first conduit 50 in response to 
operation of the fuel pump 44 is generally subject to a greater magnitude 
of pressure than the flow of fuel through the second conduit 78 which is 
in response to pulsating pressure emanating from the crankcase 26, the 
check valve 86 will be maintained in the closed position whenever fuel 
flows through the first conduit 50. Thus, the third fuel delivery means 18 
is blocked whenever the second fuel delivery means 16 is being operated. 
Similarly, when the flow of fuel through the first conduit 50 ceases by 
operation of the primer fuel control solenoid valve 46, the now unopposed 
pulsating pressure variations in the crankcase 26 will open the check 
valve 86 and pump residual fuel into the combustion chamber 12. 
In the illustrated embodiment, the check valve 86 is biased in the closed 
position, such as by a spring 88. Thus, the biasing force of the spring 88 
works in combination with the fluid pressure in the first conduit 50 in 
closing the check valve 86, thereby reducing the pressure differential 
necessary to maintain the check valve 86 in the closed position. 
Still referring to FIG. 3, in order that the flow of fuel through the 
second conduit 78 will not "back up" into the first conduit 50, a second 
check valve 90 is placed in line with the first conduit 50 between its 
inlet end 52 and its point of intersection with the first conduit 50. The 
check valve 90 is biased in a normally closed position and is unseated by 
fluid pressure occasioned by operation of the primer fuel control solenoid 
valve 46. By virtue of this construction, fuel may flow in the first 
conduit 50 only toward the nozzle 56, and no fuel "back up" from the third 
fuel delivery means 18 can occur. 
Shown in FIG. 4 is an internal combustion engine 10 which is similarly 
constructed as the one heretofore described, but which includes four 
combustion chambers 92, 94, 96 and 98 and four associated crankcases 93, 
95, 97 and 99. For purposes of further description, the combustion 
chambers 92, 94, 96 and 98 will hereafter be referred to respectively as 
the first, second, third and fourth combustion chambers and the associated 
crankcases 93, 95, 97 and 99 will similarly be referred to respectively as 
the first, second, third and fourth crankcases. 
As is shown diagrammatically by arrows in FIG. 4, piston reciprocation is 
sequenced by conventional timing means (not shown) such that the pistons 
28 in the first and fourth combustion chambers 92 and 98 reciprocate 
together in one direction, and the pistons 28 in the second and third 
combustion chambers 94 and 96 reciprocate together in a direction opposite 
to that of the pistons 28 in the first and fourth combustion chambers 92 
and 98 (i.e. as shown in FIG. 4, when the pistons 28 in the first and 
fourth combustion chambers 92 and 98 are in their upstroke, the pistons 28 
in the second and third combustion chambers 94 and 96 are in their 
downstroke). As in the previously described embodiment, the first fuel 
delivery means 14 introduces fuel into each combustion chamber 92, 94, 96, 
and 98 through suitable reed valve assemblies 40 which communicate with 
each crankcase 93, 95, 97 and 99. Likewise, a fuel metering orifice or 
nozzle 56 communicates with each combustion chamber 92, 94, 96 and 98, and 
a drain nipple 76 communicates with each crankcase 93, 95, 97 and 99. The 
second fuel delivery means 16 communicates with the fuel pump 44 of the 
first fuel delivery means 14 and with each nozzle 56 to simultaneously 
introduce fuel into each of the four combustion chambers 92, 94, 96, and 
98 through the respective nozzle 56 subject to the operation of the primer 
fuel control valve 46. In similar fashion, the third fuel delivery means 
18 communicates with each drain nipple 76 and intersects the second fuel 
delivery means 16 to return residual fuel from the crankcases 93, 95, 97 
and 99 to each of the combustion chambers 92, 94, 96 and 98 through the 
respective nozzle 56. 
In this embodiment, the third fuel delivery means 18 connects the crankcase 
of one combustion chamber with another combustion chamber in which 
opposite piston reciprocation occurs. In this way, the pulsating pressure 
differential needed to induce the flow of fuel through the third fuel 
delivery means 18 is created. 
While is should be appreciated that an arrangement of check valves similar 
in construction to those heretofore described and shown in FIG. 3 may be 
utilized, in the four cylinder embodiment shown in FIG. 4 through 7, two 
fuel distribution check valve blocks 100a and 100b direct the desired flow 
of fuel through the second and third fuel delivery means 16 and 18. It 
should be appreciated that one fuel distribution check valve block is 
provided for every two combustion chambers, so that in a six cylinder 
embodiment, three check valve blocks would be provided and so on. 
Generally, each check valve block 100a and 100b includes two individual 
check valve chambers, respectively 102a and 104a for block 100a, and 102b 
and 104b for block 100b. Each check valve chamber 102a, 104a and 102b, 
104is compartmentalized into an upper chamber portion 106 which 
communicates with one combustion chamber and a lower chamber portion 108 
which communicates with the crankcase of another combustion chamber in 
which opposite piston reciprocation occurs. The upper and lower chamber 
portions 106 and 108 of each check valve chamber are interconnected by 
means of a port 110. 
Referring first specifically to the first check valve block 100a, check 
valve chamber 102a channels the flow of fuel from the first crankcase 93 
to the third combustion chamber 96 (as shown digrammatically in FIG. 4 and 
schematically in FIG. 7). More particularly, and as best shown in FIGS. 5 
and 6, a drain conduit 113 connects the drain nipple 76 of the first 
crankcase 93 with the lower chamber portion 108 of the check valve chamber 
102a, and an outlet branch conduit 116 connects the upper chamber portion 
106 with the nozzle 56 of the third combustion chamber 96. The port 110 
which interconnects the upper and lower chamber portions 106 and 108 
permits the flow of fuel between the two chamber portions. Thus, due to 
the oppositely matched pulsating pressures, residual fuel is directed from 
the first crankcase 93 into the third combustion chamber 96 through check 
valve chamber 102a. 
The equivalent construction and operation are found in the remaining check 
valve chambers 104a, 102b and 104b. More particularly, and as is best seen 
in FIGS. 4, 5 and 7, check valve chamber 104a channels the flow of 
residual fuel from the third crankcase 97 to the first combustion chamber 
92 by means of drain conduit 117 which enters the lower chamber portion 
108 and outlet branch conduit 112 which leads from the upper chamber 
portion 106. Likewise, check valve chamber 102b (see FIGS. 4 and 7) 
directs the flow of residual fuel from the fourth crankcase 99 into the 
second combustion chamber 94 by means of drain conduit 119 and outlet 
branch conduit 114, and check valve chamber 104b (see also FIGS. 4 and 7) 
directs the flow of residual fuel from the second crankcase 95 into the 
fourth combustion chamber 98 by means of drain conduit 115 and outlet 
branch conduit 118. 
The upper chamber portions 106 of the individual check valve chambers 102a, 
104a and 102b, 104b are connected by the first conduit 50 in series with 
each other. Thus, fuel which is pumped through the first conduit 50 in 
response to the operation of the primer fuel control solenoid valve 46 
will simultaneously enter the upper chamber portions 106 of each valve 
chamber and will thereafter be channeled through the four associated 
outlet branch conduits 112, 114, 116 and 118 into the four combustion 
chambers 92, 94, 96 and 98, thereby priming the engine. 
In this embodiment, the second control means 86 includes a series of check 
or flap valves 122 or the like which individually communicate with the 
ports 110 in each check valve chamber 102a, 104a and 102b, 104b. Like the 
heretofore described check valve 86, each check valve 122 is operable in 
response to fluid pressure between a closed position (shown in solid lines 
in FIG. 8) which blocks the associated port 110, and thus blocks 
communication between the associated upper and lower chamber portions 106 
and 108, and an open position (shown in solid lines in FIG. 6) which 
affords communication between the associated upper and lower chamber 
portions 106 and 108. 
By virtue of this construction, since the flow of fuel through the first 
conduit 50 is generally subject to a greater magnitude of pressure than 
the pulsating pressure generated by piston reciprocation, all of the check 
valves 122 will be simultaneously placed in the closed position (as shown 
in FIG. 8) whenever the primer fuel control solenoid valve 46 is open to 
permit fuel to flow through the first conduit 50 into the upper chamber 
portions 106 of the check valve chambers. As a result, residual fuel will 
be trapped in the lower chamber portions 108 of the check valve chambers, 
and only fuel flowing through the first conduit 50 is directed through the 
outlet branch conduits 112, 114, 116, and 118 to the nozzles 56. Thus, the 
return of residual fuel is blocked when the engine is being primed. 
Conversely, when the primer fuel control solenoid valve 46 is closed, the 
unopposed pulsating pressure variations between the matched crankcases and 
combustion chambers will open the affected check valve 122 (as shown in 
FIG. 6), and residual fuel will be pumped from the affected lower chamber 
portion 108 into the associated upper chamber portion 106 and ultimately 
into the associated combustion chamber 92, 94, 96, or 98. 
As in the first described embodiment, each check valve 122 may be biased by 
suitable means in the closed position, thereby reducing the pressure 
differential necessary to maintain each check valve 122 in its closed 
position. 
Also as in the first described embodiment, the second fuel delivery means 
16 includes check valves 126 which are located at the points where the 
first conduit 50 enters the upper chamber portions 106 of the respective 
check valve chambers. The check valves 126 are simultaneously operative to 
allow the flow of primer fuel from the first conduit 50 into the upper 
chamber portions 106 in response to operation of the primer fuel control 
solenoid valve 46 (as is shown in FIG. 8) while blocking the backflow of 
residual fuel from the upper chamber portions 106 into the first conduit 
50 during operation of the third fuel delivery means 18 (as shown in FIG. 
6). 
It should be appreciated that, while only a single cylinder embodiment and 
a four cylinder embodiment of the invention have been fully illustrated 
and described herein, the invention is applicable for use in an engine 
having any number of cylinders. 
Various of the features of the invention are set forth in the following 
claims.