86 IROC tpi 305. About 4 months ago started running worse and worse. Eventually the car died on me in the parking lot at work. After getting it to start by smaking the top of the trunk floor a couple times with a light deadblow plastic hammer, i drove it home. I replaced the fuel pump, obviously, and then drove the car for about 2 more weeks when it suddenly died again and would not run hardly at all. If i got lucky, i could get it to move some, but felt like maybe 3 cylinders were trying to move the car. Died under load and had to feather the throttle up and down to keep it running. So i put some new injectors in it, and changed the fuel filter. Put it all back together and still wont start. Hooked up fuel pressure tester and NOTHING. I get fuel to come out of the schrader valve, but its so weak apparently, that it wont move the needle. I know the tester is good cause i went out and tested my wifes car with it and it worked fine. SO i just changed the fuel pressure regulator. Still NOT ENOUGHT fuel pressure. You can hear the fuel pump whine for about 3 seconds STRONG. Not a weak sounding whine. Suggestions please!

 

My '90 5.7 TPI Iroc is doing something very similar as well. It died one morning like it ran out of fuel. I figured the pump had bit the bullet. I replaced the pump, filter, strainer, and relay. It willl still whine loudly from time to time and just die like its out of fuel. Am beginning to think maybe ECM??
Am curious what your turns out to be.

 

after puttin 3 napa/carter pumps in and on walbro in mine i finally wised up and put in a factory delco

 

Well I got it to run. All I had to do was go to Autozone, by a 5 gallon gas carton, and the go to speedway to put gas in it. Then, I went home, poured the gas in the gas tank, and started the vehicle.


But, as of now, its popping, and going in and out of a smooth running state. Wont idle well at all, and I have to feather it to keep it going. I probably need to drive it and let the ecm learn its paramaters. Or my iac is junk. upper intake and plenum gaskets are brand new, injectors are brand new bosch 3's and I have no fuel leaks, and no vacuum leaks that I can find. This car is kicking my ***.

 

Oh and if you are wondering, my gauge is off by ALOT. Said I had just over a 1/4 tank......

 

Sounds like you are describing mine. The car ran like poo for about 20mins. Drove it to the store for gas 1/4 mile away. It cleared just a bit. I set the timing and it helped even more. It runs well now, but before the fuel pump was changed the gauge read correctly and now the tank is empty at just above 1/4.

 

Today I changed the oil pressure sending unit because it was leaking, I had low oil pressure, and the fuel pump works in-line with the sending unit. My oil pressure went from 20-30 psi to around 70 psi at cold idle. I rebuilt the motor a little less than a year ago and had PLENTY of doubt that it had spun a bearing or the oil pump was bad. Hopefully it will help the intermittant problems with the fuel pump as well.

 

Oil pressure switch is in parallel with the fuel pump relay which powers the fuel pump and the MAF. If the OPS were in-line with the fuel pump by itself you would experience extended cranking until oil pressure closes the OPS to turn on the fuel pump.

As long as the ECM and fuel pump relay are working properly the OPS is only a backup power source.