Fuel Problem


lkgage03
08-31-2005, 08:14 PM
I just purchased a 1984 porsche 944. It has been sitting since november and hasnt been run. We charged the battery up on it and she jumped to life. we drove it around a couple of times, shut the engine off then swept it out. We went to start it again but all it would do is just sit there and crank. It seems like that no fuel was getting to the engine, which was surprising since it had been running less than a half an hour ago for over 20 minutes. what could be keeping the fuel from getting to the engine. where is the electric fuel pump located at? at the fuel tank? i know that its a fuel problem b/c it will run for a few seconds when starting fluid is shot into it. But i was careful not to blow the heads off. :)

thanks
lkgage03

pearldrum944
09-03-2005, 08:15 PM
The pump is behind the passenger side read wheel, pretty easy to see if you look for it. While someone is cranking it listen for it hum or see if you can feel it vibrate. It could be that the pump has gone out, but a bad DME relay can cause it not to run as well.

951racerX
09-18-2005, 05:50 AM
Check the DME relay...

Check for spark, pull a spark-plug wire, stick a spare plug into it and lay on top of intake-manifold. Crank engine, do you see spark on that plug?

Easy to check for fuel, just unscrew the cap at the end of the fuel-rail. Clamp a hose around the end and stick into cup/jar or some container. Crank the engine, do you have fuel flowing?

lkgage
09-20-2005, 03:47 PM
i thank you all for you help. i found the pump that is mounted next to the bottom of the tank on the frame of the car, but is there also an intank fuel pump? or is it just this one of the side of the frame?

pearldrum944
09-20-2005, 05:18 PM
There is only one fuel pump.

951racerX
09-20-2005, 06:56 PM
"i found the pump that is mounted next to the bottom of the tank on the frame of the car, but is there also an intank fuel pump? or is it just this one of the side of the frame?"

The pump's in the tank. The external cylinder is the fuel-filter. The pump ONLY runs when the engine is cranking or is running. You're really making this more difficult on yourself than necessary... Here's where something went wrong:

"shut the engine off then swept it out. We went to start it again but all it would do is just sit there and crank. "

What do you mean by "swept it out"? Retrace your steps and undo whatever was moved/unplugged that caused this.

pearldrum944
09-20-2005, 10:34 PM
The pump's in the tank. The external cylinder is the fuel-filter.
What? No.

lkgage
09-20-2005, 11:41 PM
i swept the car out with a sweeper. nothing to do with the engine. thank you for ur help. but there is not a fuel pump in the tank. it is right next to it. i know this because i have removed it. thanks pearldrum you have answered many of my questions so far.

951racerX
09-21-2005, 01:52 AM
What? No.

Yeah, sorry, brain-fart. Been staring at a Mustang too long this week. Fuel pump's hiding under the plastic cover next to the tank.

It's highly unlikely it's a fuel-pump problem anyway, they don't die suddenly. Usually makes squealing noises and reduce fuel-flow as they go bad. Here's how you test the pump:

1. remove end-cap from fuel-rail (don't lose that ball that falls out)
2. attach hose to end of rail, stick into cup/soda-bottle/etc. to catch fuel
3. yank DME-relay off relay-board
4. turn key to ON
5. make small wire-jumper and connect pins #30 and #87b on the DME-relay socket on the relay-board

This will turn ON the fuel-pump, you should hear it whirring away and see fuel flowing out of the hose attached to the end of the fuel-rail. This simple test verifies proper-operation of the following components all at once and saves you the time of testing and replacing them all to rule them out:

- ignition switch
- harness wiring between ignition-switch and relay-board
- harness wiring between relay-board and fuel-pump
- fuel-pump
- fuel-filter
- fuel-pressure regulator

I suspect it's the connectors for the speed & reference sensors at the back of the intake-manifold. They're 3-prong rectangular connectors held on a metal bracket at the rear along with the circular O2-sensor connector. These are not weather-proof connectors and will corrode with time. So inspect the connectors, pull them out and clean the pins, re-insert. Don't get them mixed up as they're the same.

pearldrum944
09-21-2005, 02:15 AM
I suspect it's the connectors for the speed & reference sensors at the back of the intake-manifold. They're 3-prong rectangular connectors held on a metal bracket at the rear along with the circular O2-sensor connector. These are not weather-proof connectors and will corrode with time. So inspect the connectors, pull them out and clean the pins, re-insert. Don't get them mixed up as they're the same.
Those sensors are a bitch to get to as well. When mine went bad I spent a good 5 hours replacing them. To remove 2 bolts and the sensors!! (well, my sensors were frozen into place and just shattered.) There is a way to check them, I can't remember which pins it is though. Search on rennlist, it's been discussed several times (link is in my sig)

edit:but those sensors control spark. So those should be fine if it fires up on starting fluid. So yeah, test the pump.

951racerX
09-21-2005, 03:42 AM
The speed & reference sensors controls everything to do with the fuel & spark. They tell the computer how fast the engine is turning and how far away from TDC it is. If either one of these sensors are bad, you won't get spark and you won't get fuel.

Actually, I was just talking about the rectangular connectors for the sensors. Due to age, the plastic housing on the connectors can crack and the plugs and pull apart ever so slightly, causing a loss of signal.

Simple enough to test the sensor's output signals. If they are bad, then replace them. The output should look like this:

http://www.ururacing.com/ImagesMisc/Porsche951SpeedRefSignal.gif

It's labeled 951, but the 944 signal is the same. The important part is to make sure the peak-to-peak voltage spread is at least the minimum amounts specified.

But, I doubt the sensors went bad that suddenly. Usually they start getting lower voltage outputs and the car starts sputtering and stumbling as you drive.

So for now, just unplug the sensors at the connectors in the rear of the intake-manifold. Clean up the pins, re-insert firmly and see if the car runs.

lkgage03
09-21-2005, 11:38 PM
i bought this car for $325 dollars at a farm auction. i had no idea of anything that had happened to it in its past. they said it had been sitting since last novermber at the auction yard. we brought it home like i have said before tried to get it running. we then figured it was a fuel system problem (thanks to you guys !!!) from this forum. i talked to my friends father about the problem who works volkswagons all the time. since we had already put a new DME relay in and a new fuel pump fuse in. he suggested taking off the fuel pump and touching it directly to the battery. the fuel pump looked as if it had been recently replaced (although i dont know this for a fact) it was bright blue and had no build up of crap and dirt of anykind..looked brand new in fact.

but as i was taking the pump off, i noticed that there was a 'dried blood' color, or brownish wire connected to negative terminal of the fuel pump and a black w/ a white stripe attached to the positive terminal.

but anyways. i connected to wires to the terminals and then touched the end of those to the battery (pos to pos and neg to neg) i made sure i connected it right. the only thing i felt it do was kick once while it was in my hand. but it did not spin.

is it possible that some idiot who owned it before me, connected the wires wrong on this new fuel pump before i got it? and burned it out or something?

again, i have not spoken with or did not know who owned this vehicle before me. so as of right now, the only logical thing to me is that the fuel pump is bad since it will not run when i connect it directly to the battery. and i need to buy a new one.

am i correct on this assumption?

i thank you guys greatly for the help you have given me and appreciate it greatly.

951racerX
09-22-2005, 02:40 PM
Hmm, so you hooked the pump directly up to the battery and it doesn't spin? Strange that it would die suddenly, they usually don't fail that quickly. Since it's a DC motor, if the previous guy had hooked it up backwards, it would just pump fuel in reverse. So that's not the problem either.

You're working on this problem from the individual components back up the chain. To troubleshoot that way, you have to replace everything from the pump all the way up the chain to the injectors.

Here's my prognosis of what will happen:

1. replace fuel-pump, crank car, no start, no fuel
2. replace fuel-pump wires going to pump, no start, no fuel
3. replace fuel lines, no start, no fuel
4. replace FPR-fuel pressure regulator, no start no fuel
5. replace all vacuum hoses going to FPR and fuel dampener, no start, no fuel
6. replace all injectors, no start, no fuel
7. replace all injector wires & connectors, no start, no fuel
8. check DME computer, replace DME computer, no start, no fuel
9. check AFM, replace AFM, no start, no fuel
10. check speed & reference sensors, replace sensors, maybe fuel, maybe start.


BTW, you have an alarm?

lkgage
09-22-2005, 09:08 PM
nope. unless there is a factory one on it. there is no aftermarket alarm on it

pearldrum944
09-22-2005, 09:16 PM
If there is a factory alarm there will be another lock behind the driver's door handle on the rear quarter.

lkgage
09-23-2005, 05:42 PM
than yes, there is a factory alarm. i do not know if it works or not though. does it take a different key or does the ignition key work in it?

951racerX
09-23-2005, 06:25 PM
than yes, there is a factory alarm. i do not know if it works or not though. does it take a different key or does the ignition key work in it?

The alarm comes before the DME-relay so if it's malfunctioned, you'll have no fuel and no spark. Here's the sequence of events to start the car:

1. key ON, battery-power flows to alarm box
2. if alarm OFF, alarm passes power to 1/2 of DME-relay
3. DME-relay powers on DME
4. key to START
5. DME powers other 1/2 of DME-relay (fuel-pump power)
6. DME squirts some blind fuel to start
7. car starts, DME check AFM-voltage
8. DME adjusts fuel based upon air-flow volume.

There's A LOT of components that can cause a no-start condition. You'll have to replace just about everything until that 1 out of 20 part that's bad will be replaced, quite a crap-shoot. So... test ALL of the components at once first:

1. TEST SPARK: pull out one spark-plug wire, stick a spare plug into it and lay on top of intake-manifold, crank car, DO YOU HAVE SPARK?

2. TEST FUEL: remove 4-bolts holding fuel-rail to intake-manifold, pull up rail with all injectors attached. Put little paper-cups under each injector to catch fuel, crank car, DO YOU HAVE FUEL?

That's it, simple test that will inspect the entire system. The important data here is IF you don't have BOTH fuel AND spark, that indicates one problem. But if you only have spark and NO fuel, that's another sign. Or if you have no spark, but ONLY fuel, that points to something else. So we need to collect this data and that'll help pinpoint where the problem is.

You sure the fuel-pump doesn't run when hooked up to 12-volt power directly? Are you using the battery? Or a charger? What's the voltage of the supply?

lkgage
09-30-2005, 07:23 PM
hey guys i just wanted to thank you all for ur help. the porsche only neeeded a new fuel pump and fuel filter. she is runnning so smoothly you wouldnt believe it. especially for her age. thanks again
josh

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