codetoad

iTrader: (2)

Car: '92 SC 300 manual
issue: fuel pump stays on with key off.

Is my fuel pump supposed to stay running when I jump Fp to B+ even with the key off? My first thought is yes, since it's drawing current directly from the battery with the jumper in, but I believe others have said that their fuel pump turns off with the key off, using a jumper from Fp to B+.

I've had fuel pump ECU issues and i've been able to start the car fine with a jumper, but when i turn the key off, the fuel pump stays running. Any idea why the fuel pump relay is still getting power? Also, when I ordered a fuel pump ecu on ebay, the car started up fine, gradually ran worse as it got hotter (no codes), then the car died. the fuel pump ecu i ordered was used and probably junk...but then I heard the fuel pump continuing to run with the car off - no jumper. I unplugged the fuel pump ecu and it shut off. then I plugged i back in, and nothing. It dosent seem to even work anymore.

Anyways, if the fuel pump ecu is fried now, it still seemed as if something is causing the fuel pump relay to always be powered.

Anyone else ever heard of this problem, or had it themselves, or know what is causing it? Also will the 12v mod correct this? Is the pump supposed to cut off with th key off with the 12v mod done? (I really DON'T want to cut wires if I dont have to, and if it's not going to work.)

codetoad

iTrader: (2)

Please move this to the performance forum, it was late when i posted this..

god my car is tormenting me.

aliga

iTrader: (147)

replace the fuel pump ecu, see what happens. i have one for 25 shipped if you need it.

ERXRX7

a Friend helped me trouble shoot mine. I had the 12v mod done, but they had wired it to some weird ignition source so it would occasionally stay on for a long time after car was off.
I did the bypass FP ECU mod (4prong relay) and it still did it, so we just wired it to the grey wire going to the rear of the car and it turns off when car is off and gets 12v.

codetoad

iTrader: (2)

Where was the ignition source it was wired to?

kyoso23

Does it have anything to do with your ignition switch mang?

codetoad

iTrader: (2)

It might, i've thought about that, but haven't checked. Worth a shot if the ecu aliga sends me dosen't affect it.

codetoad

iTrader: (2)

OK! I'm on my THIRD Fuel pump ECU! Nothing changed..sometimes the pump will kick on with the key on, then ill turn it off, and try it again, and the pump wont kick on at all.


So I jumped Fp to B+. I'm done buying fuel pump ECU's...I just want to know WHY my fuel pump stays on with the key off and if I can fix this problem by simply wiring in a toggle switch once I do the 12v Fuel mod. THANKS!!

codetoad

iTrader: (2)

Update:

I believe the issue i'm having lies in the Main Relay of the 1992 5 Speed SC 300 ECU (M-REL on the wiring schematics),

What is happening is, M-REL on the engine ECU is faulty. It is stuck closed permanently and it is causing the circuit to stay grounded with the key off. This problem may of been caused by my original faulty Fuel pump ECU.

Anyways, with M-REL never resetting, it is in turn is causing the coil side of the Fuel Pump Relay to be grounded, and closing the switch fuel pump relay itself. The end result is that the fuel pump relay, is constantly powered, caused by a faulty engine ECU, and it is never resetting to an open circuit. This is simultaneously draining my battery and causing the fuel pump to operate with the key /car off.

If you ever have this problem, replacing the fuel pump ECU will NOT fix it. It's your engine ECU. i'm about 99% sure of this, because i've ran out of other things it could be. I've exhausted all angles, so it has to be this, or my car is just possessed.

Anyways, I have a 1JZ-GTE Swap in my garage im working on, so hopefully the Soarer ECU will fix this issue because it's been headache and such a pain in my side to diagnose. So for a temp fix to drive my car, I plan on wiring in a fuse and an OFF/ON switch between M-REL and it's ground (according to the diagrams) so I can just ground and unground M-REL myself from inside the car, whether its off or on. My battery might drain a little from M-REL staying stuck closed, but it won't be as much if the fuel pump relay isnt getting constant power. Hope this helps anyone with similar issues.

dumdumgreg

iTrader: (5)

Gazi
you still have one?