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

[jfishtaker]

j cat

Made the splice today, fuel pump runs continuously, motor starts up, runs about 2 seconds cuts off. Will crank right back up, but cuts off.
The 20 second delay is not for this engine model, when I got the component untaped to wire harness it was a omron relay 10052973. No Idea what this controls. Nice to have a wire diagram.

[MT-2500]

Originally Posted by jfishtaker

j cat

Made the splice today, fuel pump runs continuously, motor starts up, runs about 2 seconds cuts off. Will crank right back up, but cuts off.
The 20 second delay is not for this engine model, when I got the component untaped to wire harness it was a omron relay 10052973. No Idea what this controls. Nice to have a wire diagram.

Engine run 2 seconds and then shut down is the anti theft system shutting off.

[j cAT]

Originally Posted by jfishtaker

j cat

Made the splice today, fuel pump runs continuously, motor starts up, runs about 2 seconds cuts off. Will crank right back up, but cuts off.
The 20 second delay is not for this engine model, when I got the component untaped to wire harness it was a omron relay 10052973. No Idea what this controls. Nice to have a wire diagram.

the ECM is next.

[ronlindsey1]

Hi to all. Although I just signed on to this forum I have been doing DIY repairs for nearly fifty years. Owned a dozen cars and trucks and always purchased a repair manual to guide me. Seen a lot of funny problems right from the factory one that stumped me the longest was a vacuum hose that was solid rubber for about 3 inches right in the middle. I have replaced a half dozen fuel pumps from mechanical to all electrical units in the fuel tank. I found that to shut off the fuel pp in an accident there is a "crash switch" under the carpet on the passenger side that isn't tied in to the ECM in any way. Also I don't trust manufacture gauges so I always hook up a mechanical oil pressure gauge. As far as the oil pressure switch goes all the older models that had them were only wired to an idiot light. My newest vehicles ( 2004 Buick and 2010 Jeep ) don't even have a oil pressure switch or even an oil pressure gauge ?! Hope this might help.

[ronlindsey1]

Hi to all again. Mea culpa, mea culpa, maxima mea culpa. Even at my advanced age the taste of eating crow is quite bitter. I rechecked the wiring diagram for the ECM for my 2004 Buick and there for all to see was the fuel pump with two sources of power--one from the control of the power relay and one from the oil pressure switch, a pink wire that was tan in earlier models. Kudos.

[MT-2500]

Originally Posted by ronlindsey1

Hi to all again. Mea culpa, mea culpa, maxima mea culpa. Even at my advanced age the taste of eating crow is quite bitter. I rechecked the wiring diagram for the ECM for my 2004 Buick and there for all to see was the fuel pump with two sources of power--one from the control of the power relay and one from the oil pressure switch, a pink wire that was tan in earlier models. Kudos.

Ford is the only one that has a fuel cut off switch in case of a crash.
The oil pressure switch used on some older GM trucks was never a fuel cut off switch but a safety switch to keep the fuel pump running incase the relay failed.
But in the early 80's Gm did have a 3 wire oil pressure switch that would shut off fuel pump when it had no pressure after start up.

What model and engine Buick are you referring to that you think has a oil pressure shut off?

[Tech II]

Agree with MT......

[ronlindsey1]

This is primarily for MT2500. I just did a google search for fuel pump control operation and think you should read the info from EBAY about this. Search ebay for this.

[ronlindsey1]

Hey there MT-2500. After checking the wiring diagram for my 2004 Buick Lesabre in my Haynes manual I decided to read the section on Fuel systems. My oil pressure sending unit has 3 terminals ( I think it contains the oil pressure switch). In the notes section it says "If oil pressure drops below the specified pressure level, the oil pressure switch will act as a fuel fuel pressure cut-off device. " pretty interesting and more than meets the eye. Thanks.

[Tech II]

In the notes section it says "If oil pressure drops below the specified pressure level, the oil pressure switch will act as a fuel fuel pressure cut-off device. "

I believe that is wrong.....the oil pressure switch is in parallel with the fuel pump relay.......so if the relay/circuit does not function on start up, when oil pressure builds up, the oil pressure switch closes to energize the fuel pump....this is a classic example of an extended crank caused by a bad fuel pump relay....

If oil pressure drops too low, the oil pressure switch opens, but since it is an open parallel circuit, the relay circuit is still energized by the PCM, the car continues to run.....

[MT-2500]

Originally Posted by ronlindsey1

Hey there MT-2500. After checking the wiring diagram for my 2004 Buick Lesabre in my Haynes manual I decided to read the section on Fuel systems. My oil pressure sending unit has 3 terminals ( I think it contains the oil pressure switch). In the notes section it says "If oil pressure drops below the specified pressure level, the oil pressure switch will act as a fuel fuel pressure cut-off device. " pretty interesting and more than meets the eye. Thanks.

I hate to tell you but Your Haynes manual is full of crap.
Every Haynes manuals I have saw will lie to you.
They are a One book fit all like trying to putting socks on a Banty Roaster.

On a 04 Buick LeSabre the oil pressure 3 wires
One is black ground and gray is a 5 volt reference signal and the Tan/white is the oil pressure signal to PCM.
Not even close to a oil pressure safety or cut off switch.

[brcidd]

Agree with MT the "switch" you reference is actually a 3 wire pressure transducer that monitors oil pressure - same logic is used in a/c high pressure line- to tell PCM when to turn on fans and turn off compressor....

[gmc Jay]

i have a 1990 Gmc k1500 and it was running and just cut off replaced fuel pump FP relay,computer checked all grounds and nothing in my case could the oil pressure switch be the reason? im stumped

[brcidd]

Try whaaaaaping the fuel tank while someone else is trying to start it-- FP may be old and armature worn off center- whaaaaaping it can jarr it loose and it can start pumping--if so it needs replaced.

[MT-2500]

Originally Posted by gmc Jay

i have a 1990 Gmc k1500 and it was running and just cut off replaced fuel pump FP relay,computer checked all grounds and nothing in my case could the oil pressure switch be the reason? im stumped

No way.
Oil pressure switch is not a fuel cut off switch.
It is a switch to keep engine running in case the fuel pump relay quits.

Does the relay click on and send 12 volts to fuel pump key on 2 second prime up or while cranking engine?

Best to start a new thread on your problem.
Give all info and someone will help you