TeufelHei

While going to school this morning, I noticed (or rather didn't notice) that my fuel pump was silent. The car started and idled as it usually does in the morning, which is a bit slow to reach a stable idle RPM, but it did that when I could hear the pump too. I can't hear it with the key turned or with the engine running. Am I goin' deaf, last I checked the car shouldn't run without a fuel pump.

I swapped a few relays around and still no dice, everything works like it's supposed to, it's just not making any noise. Incidently, I am a third of a tank through running BG44K fuel system cleaner through, could this have some mystical lubricating property that silenced the pump?

TeufelHei

This is on the 85 by the way, the 81 is still as loud as ever.

MikeN

From what I have seen the early pumps/cars are pretty noisy.....even several magazine articles for the early cars pointed this out. With the later cars though a fuel pump in good condition should be nearly silent.......don't know whether it is the pump/delivery systems design, better sound insulation, or maybe both........but my GT pump(s) are pretty quiet......I can't hear them inside the car, and can only hear the main one a little outside. And by all means some fuel system cleaner could very well make the pump a little quieter. I have also noticed that fuel tank level will also play a part in what sounds the pump makes.

SharkSkin

Does that car have two pumps? if so, the external one may have given up the ghost, leaving you with the one inside the tank, which should be harder to hear. Be very careful while troubleshooting; do it outdoors if possible, have a big fire extiguisher and a person who knows how to use it standing "fire watch". I recommend Co2 or better yet, Halon or Halotron. If you spray a dry chem extiguisher on/in your car you'll be sorry. You'll be glad it didn't burn to the ground but you will be cleaning up the powder for a long time to come.

mark kibort

you can put a jumper across the fuel pump relay. it will activate the fuel pump, even though the car is off. (just turn the car on) this way, you can hear whats happening.

I dont remember the two of the terminals numbers, but i can get that easily if you want to try it.

mk

Rich9928p

Do you still have the electrical diganostics hand-out from the AZ 928 Desert Gang tech session? As outlined in the hand-out, relay terminals 30 and 87 are the ones to jump.

As a safety feature, the fuel pump doesn't constantly run until the engine starts. The pump just runs long enough to pressurize the system and then only kicks in when the EZF module tells the LH controller that the engine is turning. So, you won't hear anything if the engine isn't running.

Pull the inspection cover off the back of the fuel tank and start the car. Put your hand on the pump and feel if it is vibrating. If you can't feel any vibration, it is not running. If it isn't running, remove the wires and run a 12 V jumper cable to it and see if it kicks in. If it does, you have a relay or wiring problem.

To verify if you have an in-tank pump, look to where the fuel line goes into the lowest point of the fuel tank. There is a metal fitting that screws into the tank. If there are two wires plugged into that fitting, there is a pump in there. If there are no wires, you only have an external pump. As small as the in-tank pump is I doubt if it can push enough fuel to keep the car running.

A common reason for fuel pump failure is the in-tank screen breaking for falling off and crud getting into the fuel pump. I'd recommend at least once per 10 years draining the fuel tank, pulling the plug, and replacing that screen. You also will need to replace the gasket. You do need to be very careful, if you screw any thing up you may have to replace the fuel tank.

The in-tank fuel pump also has a screen, and many failures are a result of that screen breaking off too. Be VERY CAREFUL removing the leads off of the in-tank pump, if they break the pump will leak and you'll have to buy a new one!!

Good luck,

TeufelHei

Yup still got it Rich, I'll be working that out here ina bit. I wish I'd read this post before I got back from the shop, I'll just have to check when the car cools down a bit. I can't hear the pump run even when the car is running (from outside), which is why I'm concerned. I'll pull the cover tonight and check the basics. I'll jumper the fuel pump relay as well.

It's gott be working,, she's obviously using gas. I'm halfway down on a tank of BG44K fortified fuel. I ran the full induction cleaning today as well, it remains to be seen how this works. So far so good though.

Well, off to Autozone for wax. She's good looking, but high maintenance to be sure. Gotta love it.

Ben Allison

Quiet pump = good! I run marvel mystery oil through my pump every few months to quiet it down. If it wasn't working, your car wouldn't run. The in-tank pump is just a sump pump. It just helps keep the main fuel pump from over working. It's more likely that you un-froze the in-tank pump and now the external pump is quieter from less stress.

ViribusUnits

If you can hear your fuel pump, your exaust is too quiet.

The cure for a noisy fuel pump is a new exaust system. I recomend a cat by-pass if your not in a smog testing region.

heinrich

I notice that on most 928's I've owned, when fuel level is low, I hear the pump loudly, but never on a full or over-half tank .... as Viribus says though .... the white S4 ... never heard any sort of pump on that one

TeufelHei

To VU: all in good time my pretty....hehe. I'm going with 2.5" all the way back with a couple high flow cats in between and a muffler to keep po-po at bay.

Thanks for the reassurance Ben.

I've got to wax her up tomorrow morning, I'll listen for the pump then.

This makes me think that things in the 81 are not what they should be, but then she's old and she needs lots of love.

TeufelHei

No worries, alles clar commisar. Mein benzin pumpen ist in sie tanken, und ist gut und laut arbeiten. How's my Genglish?

Bill Ball

The only time I hear the pumps on my 89 is when I'm down to the last gallon of gas, but it could be the Led Zepplin concerts in the 60's affected my hearing.

SharkSkin

Having seen your idea of "taking it easy" on the SITP run, I'm guessing that the sound from the pump just isn't catching up to you.