Fuel Pump

scrambled2k3 · 10-17-2003, 01:08 PM

I think i have a problem with my fuel pump...I jumpered the relay 30 with 87 and i never heard anything kick in. The car won't start, but it will when you spray starter fluid in the intake. Can somebody tell me where the fuel pump is located, and help me out with some ideas of what i can do make sure that's what it might be?

Dark Skies · 10-17-2003, 01:40 PM

It's tucked up under the right hand rear wing at the edge of the petrol tank. If you switch on the ignition the pump should vibrate- mine has a slight hum to it as it spins. Check the obvious connections pump, grounds, relays, fuses to start with. If the pump is working but not getting fuel to the injectors it may be a dirty filter, or pressure regulator problems. If it's getting to the injectors but not passing through it could be they're blocked.

JRMock · 10-17-2003, 02:15 PM

You should be able to hear the pump run when you turn the key to ingnition on, just befor turning over the engine.

Or..

First you should remove the coil wire from the coil side...no need to have spritzen sparken in the area...then you can remove the bolt (I think 15mm) on the front of the fuel rail, and hold a big cup under it to catch fuel. Have your assistant turn the engine over for about 10 seconds. If you get a good stream of fuel, your pump and/or filter is OK.

The Hayes manual has some numbers, i.e. how many ounces per second, but I don't have the manual with me.

Good luck and be careful.

scrambled2k3 · 10-17-2003, 02:16 PM

i'll check what you said! The car was parked in a garage about 2 1/2 years ago, and hasn't been driven since. It was running fine whenever he parked it. So i thought it could be bad gas or something, but there was little gas in the tank, and i poured fresh gas in it and it still won't start. And i know the fuel lines aren't clogged from the fuel shut-off valve to the gas tank...cause i took it off and blew in it and a friend could hear me blowing when he put his ear to the gas tank.

scrambled2k3 · 10-17-2003, 02:19 PM

the fuel pump should automatically pump fuel up to the engine without turning over the engine right? shouldn't it atleast fill the lines going from the engine to the tank??

Dark Skies · 10-17-2003, 03:58 PM

Quote:

Originally posted by FR Wilk
Nope...... Fuel pump is on when the ignition is in the start position or the engine is running.

Safety feature, fuel shuts down when engin is not turning to prevent fires after an accident.

Is that something peculiar to the American imports? When I flip my immobiliser switch and turn the key to the on position my pump kicks in prior to turning the key to crank the engine.

SoCal Driver · SoCal Driver's Garage

Quote:

Originally posted by Dark Skies
Is that something peculiar to the American imports? When I flip my immobiliser switch and turn the key to the on position my pump kicks in prior to turning the key to crank the engine.

There is no difference in the wiring for ROW fuel pumps. Me thinks someone has buggered your wiring.

Dark Skies · 10-18-2003, 02:29 AM

Quote:

Originally posted by FR Wilk
Some do. Damn Britts, I was hoping to escape with only the short explanation.

It is not part of the design but some cars have the fuel pump come on when they move the key to the 'on position'. Most do not and the pumps wait for the key to be moved to the 'start position'. I did a survey a few years ago on another Porsche list and it does happen.

Quote:

Originally posted by SoCal Driver

There is no difference in the wiring for ROW fuel pumps. Me thinks someone has buggered your wiring.

Well that's a queer one an' no mistake Mister 'Olmes. I wonder if it's something that occurs when the immobilizer / alarm is wired up? Eh. But that wouldn't explain why the symptom stopped after replacing the snapped belt.

I've done / had done some quite extensive servicing under the bonnet and recently had all the fuel system off for various checks maintenance etc. and the pump still switched on with the ignition in the pre-cranking position. Many electrical connections have been unplugged / removed during my ownership and none of it has caused the pump to work as you have described once back together. I just reckoned that was how things were meant to be. Odd.

scrambled2k3 · 10-18-2003, 09:07 PM

is it hidden behind something cause i can't see it when i get under the car. Is it between the gas tank and the fuel filter or after the filter?

scrambled2k3 · 10-18-2003, 09:10 PM

and where is the 87b terminal??? i found 87a and 87...but i don't see a 87b! And do you jumper it with the slot 30 that has a fuse in it, or the empty slot with a number 30 beside it (where the big fuses go?)

AFJuvat · 10-18-2003, 09:15 PM

WHat year is your car?

If it is an 85.5 or later, it is under a plastic cover on the bottom of your fuel tank

AFJuvat

speed · 10-18-2003, 09:46 PM

200 rpm's then fuel pump comes on...

Scott R · Scott R's Garage

Had to read this thread as I about to order a pump from Pelican tonight. I did a 400 mile road trip in the 951 today, since the 911 has no radio, and no AC (It's a wife thing,) and about 300 miles in the pump started to whine.

The noise from my fuel pump is so LOUD that you can hear the whine over the radio.

scrambled2k3 · 10-19-2003, 09:42 AM

its an 86 944, non-turbo. just in case it might be an electrical problem and not the fuel pump, can somebody tell me how i can check that?

SoCal Driver · SoCal Driver's Garage

Early 944 uses pin 20 on the DME to ground the second coil and close the contacts for the fuel pump AND the idle bypass valve heater. The current for the fuel pump comes directly off off of the battery, through the second set of contacts in DME relay, through fuse #2 then splits between the fuel pump and the idle valve.

On later 944's (post 85.1) the fuel pump circuit splits to the heater in the Ox sensor. If you have one.

The wiring is the same for the turbos.

The most obvious way this can be cross circuited is by using a wrong relay. Pin 85b for grounding the second coil goes directly to the DME.