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fuel pump relay

my fuel pump doesn't work...how can i tell whether its an electrical problem, or just a bad fuel pump?

Old 10-19-2003, 08:14 PM
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How did you test the fuel pump?
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Old 10-19-2003, 08:28 PM
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i don't ever hear it turning on...i took the front bolt off the fuel rail and turned the engine over and no gas came out at all. And i had somebody continually spray gas into the intake while i started the car. The car would start and run until it burned off all the gas that was being sprayed into it. I changed the fuel filter so i know its not clogged.
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Old 10-19-2003, 08:45 PM
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Pull the DME relay and jump between the pins 30 and 87b on the socket. This will apply current directly to the fuel pump. You should be able to hear it by bending down behind the right rear wheel. Don't leave this jumper in too long.

If the jumper works then replace the relay.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Never break more than you fix!
Old 10-19-2003, 09:10 PM
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where is 87b? i have found 87a and 87. but i don't see 87b. And the 30, is it the 30 that the fuse is in, or is it one of the slots where the big fuses are. cause i see a couple of 30's by the big fuses.
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Old 10-19-2003, 09:14 PM
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is 87b under the dme relay?
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Old 10-19-2003, 09:15 PM
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What year car?

You have to pull the DME relay out and jumper the pins in the socket.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Old 10-19-2003, 09:31 PM
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If you have an early 944 you can use a short jumper from either aux fuse 3 or 5 to 2. This is the fuse rack that does not have the plastic cover on it. I use jumpers with aligator clips on them.

If you have a later model 944 with the fuses under the hood then I would jumper at the socket.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Never break more than you fix!
Old 10-19-2003, 09:41 PM
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Scrambled,
SoCal is trying to help me with a similar problem. I believe he is referring to jumpering the female connectors on the fuse/relay board itself. I have an '87 944 n/a so don't know if yours is the same vintage. You need to answer him for your model year. I can maybe help by interpreting which pins in the relay correspond to the fuse/relay board but hate to do that until we know what car you have. Sure don't want to fry something expensive.
Old 10-19-2003, 09:49 PM
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its a 1986 non-turbo. i took out the dme relay this morning and jumpered 87b with 30 while i had the key turned into the on position. I never heard any noise when i knelt down by the rear passenger side tire. But whenever i put the jumper in and pulled it out...i heard a faint knocking, but it only did it once, not consecutively. I think it was the sound of the fuel pump trying to cut on and off when the power reached it. but it never did cut off. to make sure....i also took the front bolt off the fuel rail and jumpered the two again, no fuel or anything came out.
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Old 10-20-2003, 07:35 AM
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Not good. Did you also check the fuse to the fuel pump?

If so then I would pull the cover over the fuel pump and check it for voltage when the pins at the DME socket are jumpered. It's been know to have these connections corrode on the fuel pump. By the way pin 30 is directly from the battery so you don't have to turn the key on. Use pin 86 if you want the key to turn it on and off.

Please add you car model and year to your signiture line.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Never break more than you fix!
Old 10-20-2003, 10:14 AM
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i checked the fuel pump fuse...its 34 i believe...and it was still good. but i haven't looked at the fuel pump connections to see if they were corroded or not. but i will try that.
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Old 10-20-2003, 05:03 PM
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The fuel pump sometimes goes bad. The impeller breakes loose from the motor shaft and the motor spins but no gas exits. the pump has a one-way valve on the end, and it may be stuck. If you jumper the dme relay, and hear no sound, its either the wires, the fuse, or the pump.
A way to test is to remove the pump (you need to carefully drain the tank), and hook the pump up to a power source like a battery charger.
If nothing happens, its the pump. Nopi sells the Bosch unit for less than Porsche does. About $50 - $100 less. Use the part number on the pump body to order the part.

Be careful, you are working with flammable stuff.

Its usually the dme relay, the fuse, or the pump.

Your fuel filter could be clogged too.
Old 10-22-2003, 01:55 PM
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i got the fuel pump off and the connections looked good. I hooked it up to a battery charger and it would vibrate and run. But i got jumper cables and hooked it to the car battery and it would do nothing. It just made a click sound like it was trying to cut on but couldn't. I hooked it back up to the battery charger and connected a hose to the inlet and a hose to the outlet. i stuck the inlet hose in gas and plugged in the battery charger, and i wouldn't suck gas at all.
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Old 10-23-2003, 07:20 AM
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That sounds just like what I seen before. I even cut apart a fuel pump to see what was going on inside. The body of the pump is just the motor. It has a plastic impeller driven by a plastic part that is attached to the motor shaft. The motor would spin but the plactic couplings were broken so the impeller didn't spin. On the one I did the "autopsy", the impeller was actually stuck to the pump body.

I tested mine exactly the way you described. It didn't suck gas either.


When pricing the pumps, Nopi and Porsche came up with the best numbers. Both right around $300. That was for the Bosch unit, using the Bosch part number. If I remember right, I bought the Porsche unit because delivery was quicker.

You might want to replace the dme relay while you are at it, and the filter. The new pump comes with a new one-way valve but not the rubber insulation so DON'T throw the old cover out!!

Tom
Old 10-23-2003, 07:29 AM
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thanks man...i already changed out the filter...just in case it was clogged or something. thought that might have been why it wasn't getting gas. The new pump will be in today. I'll report back after i try it and tell you if that was it or not. And i haven't thrown the old one away yet...
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Old 10-23-2003, 07:33 AM
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hah....it worked..but i'm having some other problems now...see my other post, "runs bad at idle"
thanks for all the help!

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Old 10-23-2003, 01:43 PM
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