Sean79 5spd

I am still trying to solve my problem of hestitation and decaying idle in my 79. It seems that at idle if I give a little gas to get the revs up, the idle will improve and then slowly get rougher. I then tried turning on as many accesories as possible to lower the voltage (volt meter read about 10 volts but I think it reads low by 2 volts), this led to the idle getting worse and worse. The idle improved when everything was turned off. Is it possible that the fuel pumps are not pumping enough fuel at the reduced voltage.

928ntslow

Interesting that you mention this, because I believe my fuel pump starves the electrical system also. I know it is in process of an extremely slow death like most. They whine and hum as they decline.

Every once in a while, I'll watch the volt meter drop to around 10 on the guage at idle. When I give it throttle, it almost dies, but hasn't yet.

I suspected that the fuel pump may be the culprit in this issue. Nice to see someone else is experiencing a very similiar issue.

Sean79 5spd

I actually replaced my fuel pumps recently and am now worried that these new ones may fail prematurely if not getting the required voltage. I am contemplating installing a relay which will be activated by the fuel pump power which would then supply power to the fuel pumps from a wire connected directly (fused of course) from the battery.

Randy V

What are the condition of your coil and plug wires?

Sean79 5spd

Coil, plug wires, green wire, ballast resistors, rotor are all new.

User 4221

Keith,

I had the exact problem with my '81. Voltage would drop, pump stumbles and the car would stutter until I increased RPMs.

A new fuel pump relay fixed it for me. It appeared that the high load from the fuel pump would drop voltage at the power panel and cause the ever weakening relay to release and interrupt power to the pump. Something of a self fulfilling prophecy.

HTH,
Scott

Sean79 5spd

I have been putting off replacing the fuel pump relay, not sure why. Probably because I could not see an connection to my problem, especially since I have tried running with the fuel pump relay jumpered with no improvement.

928ntslow

I probably should go the relay route too, but I know my fuel pump is going to have to be replaced at some point...guess I am just waiting to get stuck somewhere!LOL Hasn't caused any problem yet as far as fuel delivery, just whines and buzzes every other time I drive the car.

BTW, some say change the fuel filter to eliminate buzzing...didn't work on mine.

Sean79 5spd

I had buzzing too. Didn't go away until new pumps were installed. I kept the old pumps as they both still worked and could be used as a tempory fix.

Dennis Wilson

Sean,

If you hook up a direct system to the pumps you will bypass a critical safety feature that shuts the fuel off when the engine stops running. Recommend you clean all of your grounds and the connections at the bottom and back of the fuse/relay panel. Start with the grounds at the back of the car, the jump post on the passenger wheelwell and the large red wire connections at the bottom/center of the fuse panel. Then move on to the fuses and the connector labeled "T" at the bottom of the fuse panel. These areas should cover all of the connections for your fuel pump circuit.

Dennis

Sean79 5spd

Dennis, if the new relay is controlled by the original fuel pump relay, aren't the safety features still in place. However, your point is taken. I am in the process of cleaning up the grounds, have done the rear location and the chassis to engine.

Dennis Wilson

Sean,

If you use the red/green wire from the relay as your switch voltage on the new relay, the safety circuit will still be in place. If you use a lead from fuse 22 (fuel pump) it will bypass the safety.

On a side note, I have noticed that the brass/copper fuses I get from the big three do not corrode up like the tin/solder fuses I've used from the local auto parts store. May want to check yours.

Dennis

Old & New

What is the (minimum) voltage at which the ignition module will fail to operate properly? I thought I saw it as "10" somewhere. Might this be the behavior you are witnessing?

Sean79 5spd

Thanks all for your input. I now have a few new avenues to pursue for this problem.

Installing new fuel pump relay today. Will probably tear out fuse/relay board this weekend for good cleaning.