well lately i've been trying to figure out about this little annoying fuel pump problem i've been having. After shutting down every now and then the fuel pump continuously stays running...after awhile it will shut off on it's own.

Now it's been a couple of years since i've have installed a new fuel pump.
I've also have replace the F.P. Relay. In fact a couple months back i've also replaced the MAF burn off relay which was was causing a trouble code to come on....(it does hook in line with the fuel pump relay)

-now i have attempted to disconnect the relay to see if the pump will go off To my amusement it didn't! Now you would think the pump would shut off after disconnecting the power source for it. I even disconnected it's fuse and it even then it didn't stop the pump from running. Now I can come up with a bunch of conclusions and possible situations....however I just happen to purchase a beat up Pontiac Service Manual (for 10 bucks!) from the swap meet at Morris (good times btw) and I found something rather interesting in the book.

I came across some thing call a "fuel pump switch."

What it turns out to be under the Fuel Pump Electrical Circuit, there's a backup system to the fuel pump relay. The fuel pump can also be turned on by the oil pressure switch. This switch is located on top on the engine block in the back, near the distributor. Now this does splice with the relay, but it also bypasses the relay as well. When the F.P. Relay fails, the switch will close and run the fuel pump.

Looking at the wiring diagram it's shows that the "fuel pump switch" has a wire that is spliced to another wire that is going to the F.P. relay, which is hot at all times, and another which is a TAN/WHT wire that goes in multiple directions to FP relay/ECM/ MAF burn off relay/fuel pump.
Now i know it's kinda hard to see without a wire scematic and i already drew out the diagram on how the whole system works...when i have a chance i'll post the illustration and show my results..

The only real test comes to mind is that i have to try and disconnect the switch when the problem is reoccuring. Hopefully i will find my answer there.

My question to you guys is...has this situation ever happen to you?

 

Replace the oil sending unit and problem solved.

Been there and done that :-)

Common problem and common fix.

Seen it a couple times on other peoples rides.

If you've replaced the relay and checked the wiring, relace the sending unit.

Its made in the event of fuel pump relay failure kick the pump on once 4psi pressure reached.

later
Jeremy

 

Hey Jer, can you use the oil pressure sending unit with the indash gauge in an 91 Camaro w/o the TPI system still hooked up??

I looked at some wiring diagrams and can't figure out if i am able to run power/ground/sensor wires from the sensor....figured you are the third gen wiring guru, or so it seems.

 

guages should still work fine regardless of the ecm being in place, at least that's how every thirdgen i've ever converted over has worked out

 

yeah but the original wiring harness was messed up so i only kept the pig tails from the sensor

plus i cant find a wiring diagram for the sensor itself to find out which wire does what