Bad FPCM...Pic

[Locknut]

The FPCM abd the relay went out....but the pump was waveformed and looks good. Check out the pic of the FPCM. It didn't melt the ground to the pump...it melted the plastic connector on the side. Go fiqure...Bad FPCM...good pump....how can that be?

[Q45tech]

That's one of the high current transistors that act to limit the voltage to the pump.

It failed from the pump running too slow and drawing more current than it could handle! It tried and tried while you ignored the sound and finally had to comitt suicide to save you.

Replace all{pump fpcu, and relay}!

[Locknut]

Well...you're making me feel guilty...but honest, I replaced the pump 20k ago and this one isn't humming at all. It was ohmed and waveformed and commutators supposedly look good. I did notice the previous owner had a fuel filter that looked like it hadn't been changed in a LONG time....so I just changed it...other than that...I'm stumped.

91 Q 110K

[Q45tech]

Power transistors usually have multiple dies in parallel in same housing, the previous pump probably stressed some of them and the new pump stressed the rest................eventually POW.

AS I keep mentioning the dealers change both items to avoid comebacks during the 12 month warranty...............knowing that there is a high likelhood that the FPCU could fail or start acting erratically.

You are dammed if you do or not too high a repair cost or trying to explain why you didn;t do both at the same time or just why there are two things.

I always keep a used working spare in my trunk, as I am on pump #3 but FPCU #2 with a double alligator clipped piece of ground jumper wire........it can hanging on the fuel tank while you get time to properly replace the FPCU. Better than waiting for and paying a flat bed on the side of interstate in a snow storm.

[Locknut]

I'm ordering the pump from Joe tomorrow...I tried to jump the pump to ground from the number 4 pin on the FPCM connector (tangaloras post)just so I knew how to do it...but it wouldn't work(maybe cause it was 14gauge wire?)...even filed the alligator clips down...quess this just isn't my day. I'm not going to take any more chances on coasting to a stop on an express way in sub zero temps this winter (with a ten year old crying for Mom)

Thanks for your advice...

[maxnix]

Locknut, I think you have the best solution. Get the O ring also, and maybe another fuel filter and a couple of cans of BG44K when you order.

Oh, and check your tank very carefully.

[Q451990]

I still wonder if the old pump stressed the FPCU. At 20K, I can't imagine the new pump being bad! If you're in to soldering and playing around with this - you can order those transistors from an online parts place like Mouser.com

I don't disagree that the best course of action is to replace everything - but a 20K pump failure with no humming noise would be a first to my knowledge.

Heath

[Q451990]

Here's a thread with part numbers for those transistors and other roasted parts.

zerothread?id=92777

Heath

[DrewQ45]

Got a few good FPCUs laying around. Make me an offer.

[elwesso]

I still wonder if the old pump stressed the FPCU. At 20K, I can't imagine the new pump being bad! If you're in to soldering and playing around with this - you can order those transistors from an online parts place like Mouser.com

I don't disagree that the best course of action is to replace everything - but a 20K pump failure with no humming noise would be a first to my knowledge.

Heath

i agree. im inclined to think that wont do anything...

Ive heard of the ground for the fuel pump controller going bad.... search for a fuel pump by user "5seryan"

[Locknut]

Well....I ordered the new pump from Joe just because none of it made any sense and I got nervous but I also lucked out and got a used FPCM from a 94 Q for 45bucks on Ebay...for a spare. I'm going to see if I can fix my bad FPCM and pass it along for cost to anyone here on NICO just as a little payback for all the good advice. Cars doing great now...too bad I'm out $573 for the new FPCM, 40 for the relay, 275 for the new pump and 250 for the diagnostics. Ouch....if I had been any smarter...I would have gotten the used FPCM on ebay, temped it in with duck tape...grounded it and left the old one right where it is...put in a new relay and saved some major cash. Ignorance always costs ya in the long run...