Fuel pump only turns on when you turn the car off

[Ondonti]

This happened a few weeks ago and it stopped after I cycled the ECU/Relays a few times over an extended period. Then a block from home a few days ago my fuel pump shut off. Rolled to a stop. Turned off key, fuel pump turns on.

I plan on swapping the ecu to see if thats the problem, not sure if I should just check the wiring first to see what is grounding and when. I have a few damaged ecu's that I should be able to swap without worrying.

[Vigo]

So... the car starts out normal and then at some point the fuel pump stops and won't start again until you turn the key off and then back on?

Kind of sounds like a relay issue. Does your car have both ASD and fuel pump relays?

[Ondonti]

So... the car starts out normal and then at some point the fuel pump stops and won't start again until you turn the key off and then back on?

Kind of sounds like a relay issue. Does your car have both ASD and fuel pump relays?

It does have both relays, 1994. I tried another set. Same thing.

But no, that is not how its behaving. The fuel pump was only turning on when the car was keyed off. Key on, and the fuel pump would turn off (no prime, no running while starting). The problem started on a very humid warm and then rainy day. When it first happened, cycling the relays with the key would "fix" the problem for a few moments. Then they would no longer cycle.

Problem was still happening today, fuel pump with key off. I had disconnected my fuel pump hotwire from the OEM relay to keep the battery alive but something else is still energized cause the battery was drained down to 11.6 volts after a few days.

Disconnected my computer which meant the relays would no longer activate, then I plugged in the only spare computer I have at my parents house (where the car is currently stuck). I have a note on this computer that says it will not ground the relays properly. Somehow it would now ground the fuel pump properly but it wouldn't start. Maybe its got something else wrong like coil driver etc.
Plugged back in the 5 speed computer I had been using and the car functioned perfectly. Started and ran for a few minutes. Turned off. About 30 seconds later while I was cleaning up, the fuel pump turned on. I disconnected the computer connector and went to work.

I am thinking there is something wrong with the computer, and these days, I would like to fix it rather than look for another computer (good luck with finding a 5 speed).
Proof would be to plug in the sketchy computer and see if the relay ever turns itself on with the car off. I have no idea what internals of the computer are in charge of grounding the fuel pump. Never seen any information about repairing the boards. Its done so often on Megasquirts that it makes me sad to see ours not be repaired. No documentation though

[shackwrrr]

Sounds like an ignition switch issue. Losing contact inside, turning key wipes corrosion off and it makes weird contact points.

[mopar-tech]

Sounds like an ignition switch issue. Losing contact inside, turning key wipes corrosion off and it makes weird contact points.

Look for a wiring issue, floating ground I suspect. The ASD is grounded by ECM to activate.

[Ondonti]

Sounds like an ignition switch issue. Losing contact inside, turning key wipes corrosion off and it makes weird contact points.

The car has had an ignition switch issue for a few years now. I replaced it and it had the same problem. The starter works fine but the ECU/relays loses power except when I am moving the switch on or off. I put back in the old switch since the problem didn't go away. I put a switch to turn the starter without turning the ignition switch when it was a really bad issue. The problem is not as bad but was never fixed. I don't use the cheater switch.

Look for a wiring issue, floating ground I suspect. The ASD is grounded by ECM to activate.

Edit: Lol

My fan relay, a/c, and my fuel pump relay have water inside them. They are all upside down because they have been unbolted from the fender for many years. I left the hood open two weeks ago to remind myself to do something under the hood and my wife said it rained a bit. I think they probably already had water and corrosion inside but it must have hit a breaking point on the fuel pump relay. The relays I had swapped out were ASD and starter relay.

This explains why my radiator fan has been tough to turn on, even with my cheater starter switch swapped over to the radiator fan relay. Explains why we started to overheat on a 10-20mph section of our NW FWD mopar cruise. Fan wasn't turning on.

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I ripped open the relays to look inside, never seen inside one. The white plastic underside relays have a nice return spring and a small magnet. The black bottom fuel pump relay doesn't have a return spring and has a bigger magnet.
I will post pictures in the next day or two of how nasty these things are inside. The radiator fan relay actually looked like it had been catching some heat or short circuiting as there was damage to the plastic on the connector. That one was FULL of water and iron oxides from the metal used to work with the magnet and draw things together to make a connection.

[Vigo]

I am vindicated! But more importantly, the car is fixed.