Does a GM oil pressure switch serve as a fuel cutoff ?

[jfishtaker]

Will tie hot to wire ign when key is turned to power!!

[jfishtaker]

Jfishtaker

Hey to Chevy experts,

I straight wired fuel pump(pink wire) to ign, got 12 volts at fuel pump, good grounds, started motor cranked right up, ran about 1 to 2 seconds cut back off. Starts up everytime, could it be anything else, maybe coil??
1995 Chevy, 7.4L gas v8 Georgie Boy RV. Where can I get a wire diagram?
What does the brown/tan wire do in operation of fuel pump(maybe sending to gage?).
vin #1GBKP37N2S3318036, 1995

[j cAT]

Originally Posted by jfishtaker

Jfishtaker

Hey to Chevy experts,

I straight wired fuel pump(pink wire) to ign, got 12 volts at fuel pump, good grounds, started motor cranked right up, ran about 1 to 2 seconds cut back off. Starts up everytime, could it be anything else, maybe coil??
1995 Chevy, 7.4L gas v8 Georgie Boy RV. Where can I get a wire diagram?
What does the brown/tan wire do in operation of fuel pump(maybe sending to gage?).
vin #1GBKP37N2S3318036, 1995

I maybe wrong !

IMO the engine starts and runs because your in the 2 sec start time period. because I don't have this vehicles wiring diagram this maybe wrong about the oil pressure switch. on the s10 pick ups 1994/95 the oil pressure switch must be working to apply power to the pcm. no oil pressure on from this oil switch the PCM shutsdown injectors, and the feed to fuel pump is removed.

this is the old style of safety to prevent fuel pump run on in a accident.
no oil pressure after start no fuelpump or injectors opening. so if you jump out the fuel pump so it will continue to run the injectors will not be commanded to open and the engine will stop..if this switch or wiring/connectors are defective.

I just did a repair on the 1994 s10 which had random stall failures. the oil pressure switch next to the distributor was the problem. prior to that we had random missfires. this was a bad ICM had it tested first. with the ICM replaced engine started very fast but we still had the random engine stall at any speed.

after the oil pressure switch replacement the oil pressure reads correct now 40-55 psi.

[jfishtaker]

jfishtaker

This may or not be a clue to what wrong, when I disconnect the Map Sensor (new map sensor)engine continues to run with plenty of fuel at injectors, check engine light comes on and give a voltage code.
When you press back petal and pull into reverse or forward the fuel shuts off??

[jfishtaker]

Jfishtaker

What effect does the 10052973 ASM Module on fuel pump shutting off after you start motor? In my RV Chevy Chassis manual it list this module and defines it function as:
QUOTE
The 1990 fuel module is connected to the instument panel wiring harness. The module and instrument panel wiring harness are shipped loose and must be installed by the body builder. This fuel cycler override module is necessarey due to the lower cranking speed of the L19(454) engine. The module overrides the ECM for 20 seconds to provide fuel pressure to the injectors.
I have located this module on my RV is located exactly where manual says, my engine starts right up but fuel shuts off after 2 seconds not 20 seconds. Is there a way to check module other than replaces it??
7.4l chevy engine(1995 year)
Any thoughts or suggestions to solve problem

[j cAT]

you stated that you hot wired the fuel pump and the engine still died.


how can the fuel pump stop pumping if you have it connected directly to the ignition feed circuit ?

my guess is that the engine is not getting a spark command because of a loss of engine run info. if the pcm does not get any engine running info the engine will not get spark or injector operation.

so what is happening exactly with this hot wire bypass ? I suggest you hook up fuel pressure guage to determine whats not working correctly. see if you get injector grounding signal . see if your loosing spark..most likely with everything hooked up correctly your loosing fuel pump,injector grounding and the spark ..........

[jfishtaker]

The straight wire done the same thing, engine cranked ran about 2 seconds and the injector fuel flow stopped. I put everthing back to normal.
I found this in my Chevy Motor home manual, 10052973 Module Asm, which overrides the ECM and keeps the fuel flow for 20 seconds. I have found location on RV, exactly where manual says it is located. Based on the description in manual must be back cause engine only runs about 2 seconds instead of 20 seconds. I assume the 20 seconds would allow the engine to reach oil pressure and continue running fuel to injectors???

The was used 1990 to 1995 engine model with 454 engines per manual!! If you go ACDleco and punch in the module no. it give you models used. Question is how to check it or just buy new and hopoe it works.

Grounds are good and spark.

[j cAT]

Originally Posted by jfishtaker

The straight wire done the same thing, engine cranked ran about 2 seconds and the injector fuel flow stopped. I put everthing back to normal.
I found this in my Chevy Motor home manual, 10052973 Module Asm, which overrides the ECM and keeps the fuel flow for 20 seconds. I have found location on RV, exactly where manual says it is located. Based on the description in manual must be back cause engine only runs about 2 seconds instead of 20 seconds. I assume the 20 seconds would allow the engine to reach oil pressure and continue running fuel to injectors???

The was used 1990 to 1995 engine model with 454 engines per manual!! If you go ACDleco and punch in the module no. it give you models used. Question is how to check it or just buy new and hopoe it works.

Grounds are good and spark.

this module is bypassing the oil pressure switch for 20 sec ? this is because of the time it would take to build up pressure ?

did you replace the oil pressure sender / switch ? could be it is the problem.

[j cAT]

I looked up your engine and it does have an oil pressure switch. this is similar to the 1994 v6 s10 that was stalling intermittently on me. this part also gave false low oil pressure readings which added to this stalling..

DID YOU REPLACE THIS PART ? IT IS NEXT TO THE DISTRIBUTOR .

[jfishtaker]

Yes I replace the oil pressure switch last week, after reading the forum information on the oil pressure switch I sure thought you guys had solved the problem. Maybe engine needs more time(which the 20 seconds ASM 10052973 gives by overriding the ECM) to build enough pressure for oil pressure switch to keep the fuel going to injectors?? I have ordered a new ecm module $38 bucks.

[j cAT]

Originally Posted by jfishtaker

Yes I replace the oil pressure switch last week, after reading the forum information on the oil pressure switch I sure thought you guys had solved the problem. Maybe engine needs more time(which the 20 seconds ASM 10052973 gives by overriding the ECM) to build enough pressure for oil pressure switch to keep the fuel going to injectors?? I have ordered a new ecm module $38 bucks.

did you measure the oil pressure ? the distributor cAM/ROD GOES INTO THE oil pump.

[jfishtaker]

Oil pressure is 40psi Plus depending on rpm's.

[j cAT]

Originally Posted by jfishtaker

Oil pressure is 40psi Plus depending on rpm's.

40 psi at idle is good. when cranking can you get it to 40 psi. when it was starting did the oil pressure shoot up quick. sometimes if the lifters leak down it takes longer to build pressure on start.

could be that 20 sec delay component.

jump out the oil pressure switch see if that allows start. then that would eliminate that. the ECM is part of the circuit so it could also be that.

[jfishtaker]

There is a orange wire,tan wire and grey wire, which would be used to jump switch??

[j cAT]

Originally Posted by jfishtaker

There is a orange wire,tan wire and grey wire, which would be used to jump switch??

according to my 1994/5 s10 diagram the orange is the feed 12volts from the ecm fuse. this goes to the switch of this oil sender/pressure switch. the other side of the switch is the grey wire. that wire goes to the ecm input and the fuel pump motor. so I would jump the orange to the grey wires. they should also be a bigger sized wire to handle the current .

the tan wire would go to the oil pressure guage. the body of the unit is ground.