Anyone know the name of the sensor thats right above the oil filter.Its not a oil pressure switch,and it doesnt come up at the auto parts store.anyone know what it does??

 

do have a pic???? i know at my work (i work at O'Reilly Auto Parts) we have a Borg Warner picture book full of sensors... might try that.... what parts store did you go to and what kind of car ya got??

 

if its mounted on the block, it might be the temperature sensor or knock sensor..but isn't the oil pressure switch mounted up by the distributor? or is that just the sending unit?

 

88 transam 305 tpi digital dash and digital oil gauge,i think it works the digital gauge.I went to advanced auto.i cant get a pic of it.

 

On Montes the oil pressure sending unit (not the same as the switch) is mounted here.

 

On my '88 IROC the sensor above the oil filter is a normally open oil pressure switch (closes with about 6psi,) it switches 12v to the fuel pump from a 20amp fuse near the battery.
This fuse also switches 12v to the fuel pump and the MAF relay via the fuel pump relay which is controlled by the ECM.

Should the Fuel Pump relay fail during engine operation the fuel pump will continue to run with 12v from the oil pressure switch.

if on engine restart the fuel pump relay remains inactive the pump will run once the oil pressure is sufficient to close the oil pressure switch, which just means a longer crank time.

 

I think the one he is talking about is the oil pressure sender for the gauge on the dash, the brass canister looking thing by the distributor would be the switch. (Correct me if I am wrong).

 

yes you are right it ties into the fuel,i saw that on the wire diagram.When i go to the autoparts store only the switch pops up,the one by the distributor.i will have to get it from somewhere else.thanks guys

 

Red tail. I just replaced this sensor myself and had a little trouble finding the name too. The dealer and most parts stores call it a "FUEL PUMP CUT-OUT SWITCH". This sensor controls the power to your fuel pump after the engine is started and has pressure. If your oil pressure fails then this switch ( sensor) shuts off the fuel pump. I hope this helps.

 

If your diagram is like mine you'll see that both the Fuel Pump Switch (oil pressure switch,) and the fuel pump relay must fail for the fuel pump to be "Cut-Off."


I don't know what year the fuel pump cut-off switch circuit was changed to function as a power backup switch.

 

So far as I know, that switch was ONLY back up power for the fuel pump. If it were a cut off switch, then your car would NEVER start until oil pressure came up, leading to long crank times all the time. In later years, I think the pressure sensor was combined with it as well. Not sure on the last.

 

!00 % correct.
I've looked into this many times and it only RUNS the fuel pump if the relay fails.
There is no cut off about it.
The ECM will read adistributor pulse and fire the fuel pump relay each time.
If the relay fails the oil switch will operate the pump so you aren't stranded.
It will make for long cranking times until oil psi rises and the pump turns on.

 

Well there seems to be many opinions about this, I may be wrong as I too am issues with My fuel pump prime. The info I recieved was directly from the GM tech at the dealer. The part thru GM is listed as a FUEL PUMP CUT-OFF SWITCH. I have spoke with Two dealers and a family member that is a GM tech for 20 some years and they all tell me the same. This sensors only job is to shut down the fuel pump if the motor has a loss of oil pressure. If its ONLY a back up. try unpluging this sensor .. See if you car still runs.

 

It does!, I have done that on mine to confirm therelay was working.
Look at the schematic, I'm not making this up.
If the relay is on, how can the pressure switch possibly turn off the pump?
Not possible.
I will content one possible option.
In the control of the FP relay, The ECM hardware sets it to on each time a distributor reference pulse is detected. I know for fact this is true (confirmed it multiple times)
Now that is during cranking and have not confirmed the relay stays engaged when running. Never looked at the relay after it was running above 300 rpm.
I do not see anything in the ECM code that would remove the FP output when the engine is running (AUJP, SD system) That is not to say on some software the relay is dropped when running.
That would be the ONLY way the pressure switch could shut off the pump.
I would love for someone else to confirm it by pulling the FP relay when the car is running. Oil switch will keep the pump on (as it should).
Then, Unplug the pressure switch and just run off the relay and see if it ever does turn off.
I'm pretty certain it will not drop out.