GM fuel pump modules

[Bitsyncmaster]

You usually can see the + and - sides on the pump itself. I used the multimeter on one and tested the connector on the top of the module to figure the power pins. The other two are for you sender sensor. I wouldn't trust the color convention. Also swap the higher gauge wires to match your pump pins if your connector happens to be different.

+1
The side that plugs into the pump the cap pulls off and then you can release the pins and move the wired pins to other locations. I was not sure which pump wire was +12 and which was ground. I guessed correct but tested with it reversed anyway and no fuel flowed reversed.

[CFI]

Well I’m happy to report that after putting this off for months I finally installed a GM fuel pump module. I decided to go with a Delphi FG0089 unit. It’s readily available at most parts stores or your favorite online retailer. It works just fine. I took my time and still had it finished in less than 1.5 hours.

I’m not sure what kind of check valve is installed in it but I am able to restart the engine immediately after shutting it off, and after letting it sit for 1 hour. I’ll report back if I notice any problems with it holding pressure for longer than that but since I have Dave’s solid state RPM relay that primes the system every now and then I don’t think I’ll have any problems with resting pressure.

For those that choose to go with a Delphi FG0089: There was a small plastic tab on the top side that needed to be sanded off in order to fit the v band clamp but that was the only modification required. This particular unit does not come with a pressure sensor but it does have the tabs that hold one in place. Those tabs are currently in the way of the fuel pump cover plate so eventually I’ll have to come up with a solution to that (perhaps sand those off too).

[Ron]

You mentioned a missing pressure sensor. Can you tell me what one is normally used for?

[CFI]

You mentioned a missing pressure sensor. Can you tell me what one is normally used for?

On newer vehicles a pressure sensor is used to detect the absense of pressure in the tank, ie a vapor leak (or worse). It will trigger a Check Engine Light. It’s similar to the pressure sensor on the fuel filler neck on newer vehicles that will set a Check Engine Light if the gas cap is not tightened correctly or missing.

The DeLorean needs no such sensor. The GM modules are available with and without the sensor.

[Bitsyncmaster]

On newer vehicles a pressure sensor is used to detect the absense of pressure in the tank, ie a vapor leak (or worse). It will trigger a Check Engine Light. It’s similar to the pressure sensor on the fuel filler neck on newer vehicles that will set a Check Engine Light if the gas cap is not tightened correctly or missing.

The DeLorean needs no such sensor. The GM modules are available with and without the sensor.

I think my 2018 Camry also checks for pressure build up. Every so often I hear a pump running many hours after a drive and i hear the pump near the fuel tank. I checked the internet about that pump noise and it is normal. Next time I hear it I will remove the fuel cap and see if that turns the pump off.

[CFI]

I think my 2018 Camry also checks for pressure build up. Every so often I hear a pump running many hours after a drive and i hear the pump near the fuel tank. I checked the internet about that pump noise and it is normal. Next time I hear it I will remove the fuel cap and see if that turns the pump off.

I believe some vehicles periodically run an air pump to verify pressure in various fuel system components. A bad reading won’t necessarily trigger a Check Engine Light. It’s usually a series of bad readings over a set time that will do it. I’m not sure what removing your cap will do, other than trigger 1 bad reading that will get stored in the ECU.

[Bitsyncmaster]

I believe some vehicles periodically run an air pump to verify pressure in various fuel system components. A bad reading won’t necessarily trigger a Check Engine Light. It’s usually a series of bad readings over a set time that will do it. I’m not sure what removing your cap will do, other than trigger 1 bad reading that will get stored in the ECU.

I will have to look into it some more. The car has been off for many hours and a pump noise will start and run for quite some time. I would think it has something to do with not venting gas fumes.

[CFI]

I will have to look into it some more. The car has been off for many hours and a pump noise will start and run for quite some time. I would think it has something to do with not venting gas fumes.

I'm sure that's what it is. Checking for evap system leaks.

[Josh]

the pressure sensor is a critical component to the EVAP system. It triggers the charcoal canister vent valve to open, the purge valve, as well as detecting large and small leaks in the vent side of the fuel system.
Without it the evap system does not function.

I just completed a LS swap in 2022, which retained the full evap system. I had to leave the pressure sensor in the fuel pump and tie it into the ecu

[Ron]

Are you sure it is not a valve? I know that later vehicles will periodically wait until you are in closed loop and driving 45+ MPH (iirc) constantly. It then applies vacuum to the tank, shuts a valve, waits a period of time then checks to see if the tank is still under vacuum. If not it will throw an OBDII emission code (E.G. P0457, leak in EVAP system). (Similar to what Josh posted.)
Never had to find out where the valve is located since it has always been a bad cap (95%) or a line off of the engine was damaged etc...

If it's a pressure sensor, I'd be interested in using the assembly for a non-automotive project. Possibly use the sensor to feed a shutoff, depending on its output....


EDIT: OK, after rereading all, I guess it is the part (sensor) that checks to see if the vacuum is still in the tank and/or triggers the valve at the canister Josh spoke of.