Help - Relay getting Hot, Fuel Pump shutting down

[BEAR-AvHistory]

Have an issue with fuel delivery. Car has started to get quick/short shut-downs of the fuel pump under load. The relay is very hot to the touch. Fuel pump is external & has been good for 5 years.

Any suggestions on trouble shooting would be appreciated.

[seagull81]

My first guess would be bad ground or loose positive connection.

[Papa]

Heat usually points to resistance. What gauge wire are you running for the relay output to the fuel pump?

[BEAR-AvHistory]

Thanks guys. Will pull the ground wires & clean the contact point. Do not know the wire gauge. Car runs the RF harness supplied by FFR. Pump (Walbro) is listed at 20amps

Car has a Coyote. Can wire be run from the hot with key on post directly to the pump then a pump to frame ground?

[phileas_fogg]

Is the relay close to a heat source (like a heater core)? If so, replacing the relay with a Bosch (or other quality manufacturer) rated to a higher temperature might be an easy fix.


John

[edwardb]

Thanks guys. Will pull the ground wires & clean the contact point. Do not know the wire gauge. Car runs the RF harness supplied by FFR. Pump (Walbro) is listed at 20amps

Car has a Coyote. Can wire be run from the hot with key on post directly to the pump then a pump to frame ground?

In theory, yes. But only if you add a circuit breaker or fuse. Don't run it unprotected. But that would also bypass the inertia switch in the RF harness. Which you're running, right? The fuel pump circuit in the RF panel is rated at 15 amps. So unless you're blowing fuses, the pump isn't pulling the rated 20 amps. Which is a good thing. Assuming your wiring connections are OK, as others have suggested, may be just a matter of replacing the relay. The rating should be marked on the relay. Assuming it's the original, hopefully RF put one in that's 15 amps or greater. I've had them go hot as a sign of failure. Just make sure to get one that has a sufficient rating.

[Bob Cowan]

The car has been running good for years, and now it's not. Something changed. I would change the relay first. Cheap and easy.

[BEAR-AvHistory]

Where the car stands vs last set of comments. Relay is not near a heat source, relay is a Bosch will have to check amperage, Relay has been replaced no joy, RF harness is used including inertia switch (did not think of that-thanks), no blown fuses, agree something changed trying to solve it is driving me nuts.

Question to edwardb. Would an all new wire run as referred to in my earlier post through the inertia switch with a breaker upset the Coyote 1 ECU?

[edwardb]

Where the car stands vs last set of comments. Relay is not near a heat source, relay is a Bosch will have to check amperage, Relay has been replaced no joy, RF harness is used including inertia switch (did not think of that-thanks), no blown fuses, agree something changed trying to solve it is driving me nuts.

Question to edwardb. Would an all new wire run as referred to in my earlier post through the inertia switch with a breaker upset the Coyote 1 ECU?

No, the inertia switch shouldn't bother anything, assuming it's wired like in the RF module, e.g. though a relay and then break the ground circuit. The inertia switch can't handle the full current of the fuel pump. I say that with no knowledge of the Gen 1 control pack. I've only done Gen 2 and Gen 3. But it's pretty simple electricity principles.

Having said that, I'm still suspicious of what's really happening. If you have a high-quality Bosch relay, and have replaced with no change, agree the relay wouldn't seem the problem. But the RF fuel pump circuit is rated at only 15 amps. Assuming you have it wired so the fuel pump is pulling through that circuit (e.g. not just powering the inertia relay) and it's not blowing fuses, then something else is happening. Not sure how re-wire changes things. But that's just a semi-educated guess.

[J R Jones]

Locating electronic devices for serviceability has it's advantage. Basic electronics is resistance in a device causes heat. Two elements make-up a relay, the contacts which should have no (closed) resistance and the coil has resistance. If you do not have the resistance specs on the relay, use a similar relay and compare resistance across the contacts and the coil. Obviously you have to actuate the coil to close the contacts for measurement. Or just install a different relay.
Is the relay rated for the 20amp load?
There could be a short to ground failure between the relay and the pump but that would make the wire hot too.
jim

[Norm B]

This could be a which came first "the chicken or the egg"scenario. The pump could be nearing failure which is adding resistance to the circuit and heating the relay. I have had electric pumps fail with the same symptoms you are having.
If you have access to the pump while the engine is running, touch it and see if it is getting hot.

Good Luck

Norm

[Papa]

I agree with Norm. If the pump is failing, or working extra hard due to a clogged filter, that could cause the symptoms. My car started shutting off late last season for no apparent reason. After the pump started making a lot of noise, I discovered the inlet was almost completely clogged. The pump was failing as a result, which was causing the other symptoms.

[J R Jones]

I recently had an MR2 (in tank) fuel pump sock clog with a vandal's silt so badly, the engine would lose power. When the silt fell off the screen, the engine would run until it loaded up again. No relay and no fuse issues, but this was an engineered system. The design intent should be for the fuse to react to a ground/load fault, not the relay. Your fuse or relay spec may not be appropriate.
BTW I had to power wash the MR2 tank clean and replace the fuel pump.
jim

[Nigel Allen]

If you have installed another brand-new relay and it is still running hot then the next place to look is the relay socket. If the socket is corroded or making bad contact with the pins of the relay, that heat will be transferred into the relay itself. Corroded socket or pins that are failing to make good contact will lead to low voltage conditions at the fuel pump. Take a real good look at the socket and also the pins on the relay to look for any high temperature discolouration or arc marks. A good quality relay like Bosch should be able to run at its full rated current without overheating and in any case a fuse of a suitable lower rating should be blown first.

HTH,

Nigel

[BEAR-AvHistory]

If you have installed another brand-new relay and it is still running hot then the next place to look is the relay socket. If the socket is corroded or making bad contact with the pins of the relay, that heat will be transferred into the relay itself. Corroded socket or pins that are failing to make good contact will lead to low voltage conditions at the fuel pump. Take a real good look at the socket and also the pins on the relay to look for any high temperature discolouration or arc marks. A good quality relay like Bosch should be able to run at its full rated current without overheating and in any case a fuse of a suitable lower rating should be blown first.

HTH,

Nigel

Winner!! Pulled the panel down, green s**t inside the socket. Will take it apart this weekend & see if I can clean it out. Expect water intrusion leaked in & caught the very end of the panel.

Have some spray electronics cleaner but looks like I will need to find something to scrape it out.

[Norm B]

Glad you found the issue. That's the good news. The bad news's, if water got into that socket, it most likely got in some or all of the others. That could be an electrical fire looking for a time and place to happen! I would very carefully inspect all contacts in the panel.

Good Luck

Norm

[BEAR-AvHistory]

Glad you found the issue. That's the good news. The bad news's, if water got into that socket, it most likely got in some or all of the others. That could be an electrical fire looking for a time and place to happen! I would very carefully inspect all contacts in the panel.

Good Luck

Norm

Agree. The panel is in a place where I can drop it down & get at both sides to check it out.

[BEAR-AvHistory]

Thanks to all. Car is back to running as good as new.