Intermittent crank/no start - start... occasionally stalling

[Chrisssssssss]

Hey all, 

 

I am having an issue with the my 89 not starting and will sit there and crank forever. Then sometimes when you turn it off and on a bunch of times I then hear the fuel pump start to whirr and then it will start. Sometimes it will stall after a while, sometimes keep running. It drives fine most of the time, but then it will hesitate and sometimes stall. I am definitely going with a fuel delivery problem. I am going to try and do the fuel pump manual override wiring and see if that helps. Could it be possible that the fuel pump relay is going? I believe I hear it click on when I try to turn the ignition to the run position. But is the relay only for the starting/prime sequence right after the key is turned or until the oil pressure is above 4psi then another fuel pump "run" circuit takes over as active?

 

I also searched and read up on this issue and found these guides:

 

Before pulling the gas tank, put 12V on the fuel pump priming wire (located near the master cyl) You could have a good fuel pump but the ECM is not sending power to the pump because of another sensed problem. You can also check the fuel pump relay. The ECM gives pin #5 of the fuel pump relay 12V to pick the coil. If you do not have the 12V present then the ECM is not sending the signal for some reason.

 

1) the pump only runs through the relay for two seconds when the key is first turned on then shuts off. That should be enough to get at least 20 psi

2) when oil pressure exceeds about 4 psi the fuel pump is turned on through the oil pressure switch. This does not go through the relay.

3) On my 88 the prime lead is just outboard of the a/c filter/dryer. It is a loose lead with a green flat connector. It should show 12v when the engine is running and when 12v is applied it will put power on the FP circuit.

 

Any other suggestions to really pin point the issue?

 

Thanks

Chris

[Dashmaster]

Chris, You need to test fuel pressure while doing your tests. Get a Fuel pressure gauge or borrow one from Auto Parts Store. You need to be in the 40+psi range for proper  engine performance. Without gauge you will not be able to tell if there is any pressure differences with any of the tests. If key on looks good with gauge then I see no need to do the other tests. Check the Fuel Regulator, If you have gas is coming out the vacuum line, regulator is bad, and this could be part of your issue.

[2seater]

35 minutes ago, Dashmaster said:

Chris, You need to test fuel pressure while doing your tests. Get a Fuel pressure gauge or borrow one from Auto Parts Store. You need to be in the 40+psi range for proper  engine performance. Without gauge you will not be able to tell if there is any pressure differences with any of the tests. If key on looks good with gauge then I see no need to do the other tests. Check the Fuel Regulator, If you have gas is coming out the vacuum line, regulator is bad, and this could be part of your issue.

Good advice. When in doubt, put a gauge on it.

[Chrisssssssss]

Ya. I haven't got around to dignosing it yet. I have a fuel pressure gauge somewhere... So ya, that's where I will start. Good idea. I didn't think about it that way. I will post back results.

[Chrisssssssss]

OK, So I did a bit of troubleshooting, and I believe it may be due to some old and aging wiring on a long time installed aftermarket car starter/alarm. I think it has something to do with the starter kill circuit wiring or something like that. They twist and taped a couple of the connections under the dash and I think some oxidation and/or corrosion had got to a few connections preventing something from working correctly. On a hunch I decided to check this out because I remember having problems with other cars in the past. So I found a connection or two that if I wiggle or twist at the joint with my hands that it seems to work better. So I will get back to you with the results. Gonna clean it up tomorrow...