91 Festiva GL EFI Stalls while idling or driving

[georgeb]

georgeb: You never hear OEM pumps but unfortunately I now have 2 aftermarket pumps on my cars. I am told OEM pumps are no longer available. The Delphi-made one I just put in is noisy and you can hear it start up and then diminish in pitch immediately when the key turns on. To me that is a priming sound.

So if you turn the key to ON (not START) you will hear it run momentarily?

[Movin]

So if you turn the key to ON (not START) you will hear it run momentarily?

I do not hear it anyway!! Pull the back seat and put your hand on the lines
coming out the top, you can feel it. There is a little plate to pull too. My cherokee jeep pump is as quiet as stock.

[georgeb]

On cars that run momentarily when the key is turned to ON, you can hear the fuel pump relay turn on and then turn off the pump and few seconds later. There is no such noise on a Festiva, at least my two EFI Festivas. The only way the Festiva pump can run is through the relay. And the only 3 things that energize the relay are the VAF switch, the crank circuit and the self-test connector. The VAF and self-test connector complete a circuit to ground for a pull-down in the relay and the START circuit sends 12V to a different pull-down. There is nothing in the ON position to accomplish this.

[scottyparade]

Happily ever after?

So... I think I have it figured out.



So this little bit of wiring, turns out it's pretty important. I should have taken a picture of it close up, but on the fuel pump side, a few of the wires were compromised. I fiddled about with it, and tested continuity with my DMM and put it all back together and VROOM.

I also cleaned out the fuel injectors with a ultrasonic cleaner, and now it is running real smooth-like. I haven't put it through any strenuous testing yet, but I think I'll try to find a replacement wiring harness at the junkyard. If anyone has one they want to sell me, shoot me a PM.

I'll post again once I've given it a more thorough going over.

[FestYboy]

look for burnt pins on the connectors (both sides), this is a sign of excessive current draw. you may find that you need a sending unit as well as the harness.

[scottyparade]

look for burnt pins on the connectors (both sides), this is a sign of excessive current draw. you may find that you need a sending unit as well as the harness.

Doesn't look like there is anything like that going on, but I'll double check. Now, my gas gauge has never worked, which I am under the impression might mean I need a new sending unit, so I might have to change that anyway.

Thanks for the tip!

[nitrofarm]

On cars that run momentarily when the key is turned to ON, you can hear the fuel pump relay turn on and then turn off the pump and few seconds later. There is no such noise on a Festiva, at least my two EFI Festivas. The only way the Festiva pump can run is through the relay. And the only 3 things that energize the relay are the VAF switch, the crank circuit and the self-test connector. The VAF and self-test connector complete a circuit to ground for a pull-down in the relay and the START circuit sends 12V to a different pull-down. There is nothing in the ON position to accomplish this.

I noted the same thing,but then realized he might still have had the jumper installed.

[nitrofarm]

So... I think I have it figured out.



So this little bit of wiring, turns out it's pretty important. I should have taken a picture of it close up, but on the fuel pump side, a few of the wires were compromised. I fiddled about with it, and tested continuity with my DMM and put it all back together and VROOM.

I also cleaned out the fuel injectors with a ultrasonic cleaner, and now it is running real smooth-like. I haven't put it through any strenuous testing yet, but I think I'll try to find a replacement wiring harness at the junkyard. If anyone has one they want to sell me, shoot me a PM.

I'll post again once I've given it a more thorough going over.

Good find Bud ! Hopefully its all down hill from here on.