New fuel pump and it still won't crank

[Chris Carpenter]

I just had the fuel pump and filter replaced and drove about 30 miles and I cannot get it to crank? Any help on this issue is greatly appreciated.

[Project560]

I am sorry that you are having trouble Chris. This is the best place to get advice for sure. I am just starting to sort out my own project car and have been reading lots of information on the internet about it. There are a number of common problems with these cars. Checking some of the most common ones might help you rule out some things.

The first thing that I would check is the DME relay. This procedure at Clarks Garage will help: DME Relay Information and Testing

The second thing would be the factory alarm module which has been known to cause problems. This one has info on it: Alarm System - Bypassing

The next thing would be the reference sensors that tell the computer when the engine is at top dead centre and how fast the engine is rotating. This one has the details you need: Speed and Reference Sensors - Checking, Replacement, and Adjustment

Clarks also has some general trouble shooting guidance: Troubleshooting - Engine

My DME relay and alarm module were not my problem, but the reference sensors were. If you find that your reference sensors are the problem, I can point you to the best advice if they are difficult to remove. Mine were stuck, but I managed to get them replaced with the advice provided on this forum. Good luck!

[Project560]

I just re-read your post Chris. If you can't get your engine to turn over, then battery or starter or myriad of electrical issues could be the problem. Clark's general procedure TS-01 that I included in the other post is a good starting point. If your engine turns over, but doesn't start then my other advice might be useful. Thanks.

[dgcantrell]

Wait a minute. I've found that people's use of the word "crank" is all over the map. "It won't crank" means it turns over but doesn't fire, or it could mean it doesn't turn over at all. Two different animals. IF Chris's car will turn over but not fire, it's probably the DME relay. The DME Relay is actually two relays in one. One powers the DME (engine computer itself) and the other (controlled by the DME) runs the fuel pump. People and mechanics who are not familiar with 944's will automatically think it's an expensive fuel pump failure if engine is not getting fuel.

Of all the times I've had this issue on my 87 944, it has been the DME relay (Twice). The 88 944S I got back in the spring did have a fuel pump issue. I determined that by using my 3-way jumper (like the one in the Clarks Garage link above) wire to force power to the DME and Fuel pump. Bought a used pump for $90 and she fired right up. Discovered it had bad oil-cooler seals and a seized water pump about 30 seconds into it thought. Fortunately I had the timing belt covers off inspecting the belts and saw the belt start to smoke. Shewwwww...

Anyway, try the jumper and see if it will run. Don't leave it plugged in though, terminal 30 is hot all the time and you will run down the battery if you're not driving the car.

[Bukowski]

Ok I'll chime in for purely selfish reasons :

I think it will help to know : parts, fuel, etc:
What is old?
What is new?
What is of unknown age?

[fiily]

I 2nd the DME relay since the car ran for 30 miles and now doesn't. If the starter just clicks, replace the battery or bring it to the FLAPS to have them load test it to see if its bad and if its bad, then buy a new one while your there and use your bad battery as a core.

[jeffrsmith]

In addition to Bukowski's questions

What year is it?

Is it turbo or Na?

dgcantrell also makes a good point - does it turn over and not start?

What have you done to troubleshoot the problem? or have you just come here to see if we can guess what your problem is?

We cannot help unless you give us a reasonable amount of info regarding the problem.

[Chris Carpenter]

Originally Posted by Project560

I am sorry that you are having trouble Chris. This is the best place to get advice for sure. I am just starting to sort out my own project car and have been reading lots of information on the internet about it. There are a number of common problems with these cars. Checking some of the most common ones might help you rule out some things.

The first thing that I would check is the DME relay. This procedure at Clarks Garage will help: DME Relay Information and Testing

The second thing would be the factory alarm module which has been known to cause problems. This one has info on it: Alarm System - Bypassing

The next thing would be the reference sensors that tell the computer when the engine is at top dead centre and how fast the engine is rotating. This one has the details you need: Speed and Reference Sensors - Checking, Replacement, and Adjustment

Clarks also has some general trouble shooting guidance: Troubleshooting - Engine

My DME relay and alarm module were not my problem, but the reference sensors were. If you find that your reference sensors are the problem, I can point you to the best advice if they are difficult to remove. Mine were stuck, but I managed to get them replaced with the advice provided on this forum. Good luck!

Thanks. I will check this out.

[Chris Carpenter]

Thank you all for your information. I am just getting this info so I will check it out tomorrow. To give a little more info the fuel pump was replace due to the car going dead on an earlier trip. Once it was replaced it ran for about 30 miles and has now gone dead again while driving down the road. Same as before. I had it towed to a shop and although it turns over it will not crank. That mechanic says the pump is working. Since they are not familiar with a Porsche I am reaching out to you for information. Thanks. I will try the replays and let you know how it comes out.

[Chris Carpenter]

This is a 1994 Porsche 968 non turbo.

[mlue]

Originally Posted by Chris Carpenter

Thank you all for your information. I am just getting this info so I will check it out tomorrow. To give a little more info the fuel pump was replace due to the car going dead on an earlier trip. Once it was replaced it ran for about 30 miles and has now gone dead again while driving down the road. Same as before. I had it towed to a shop and although it turns over it will not crank. That mechanic says the pump is working. Since they are not familiar with a Porsche I am reaching out to you for information. Thanks. I will try the replays and let you know how it comes out.

Engine shutting off during a trip, this sound like a classic DME Relay problem, you should remove the DME and tap it several times, then replace it, if that gets you going then it is the DME Relay. On an off chance that this does not work, it could be cold solder contacts to the high power transistors on the DME that energize the DME Relay, resoldering the contacts is the way to fix it.

Mark

[Chris Carpenter]

Everyone,

The DME relay was not the problem. I replaced it and the mechanic said the injectors were still not firing. I could understand 1, 2, or 3 being stopped up but not all 4 at the same time. Remember that this is a 1994 968 non turbo. The fuel pump was just replaced and I drive it 30 miles and it went dead and has not cranked since. It turns over but will not start. Any ideas are appreciated.

[fiily]

Do the 3 wire dme relay jumper and if the car runs, replace your DME relay again. Check the mechanics install of the fuel pump/filter, it seems very coincidental that he replaced it and immediately afterwards the car no longer runs.

Do the free troubleshooting, and don't start throwing $$$ at the no start issue until you figure out what the real issue is as many have done previously. Reading threads of people replacing every single related item to a non-start when a majority of the time its the DME, DME relay, bad fpr.

If the car doesn't start doing the 3 wire trick below and you have triple checked the mechanics work, and all of your fuses , your DME would be the next likely suspect.

The reason why I highlighted the stuff in red is because of this statement "That mechanic says the pump is working. Since they are not familiar with a Porsche I am reaching out to you for information. " ---> Doesn't fix porsche's to me means doesn't know how to diagnose them. Bring the car to an porsche Indy shop, and we don't mind the challenge either of troubleshooting.

Emergency Repairs

If you suspect the DME relay is bad and you need to move the car, you may install do so by installing an "emergency" jumper across terminals 30, 87, and 87b on the relay / fuse panel. Some folks will tell you to jumper terminals 86, 87, and 87b instead. This allows you to only run the fuel pump, DME, and injectors when the ignition switch is turned on. Seems like a great idea on the surface. However, realize that the wire supplying power from the ignition switch to terminal 86 on the DME relay is a 1.0 mm wire and is only intended to carry enough current to pickup the primary coil on the relay. The wire connected to terminal 30 is a 4.0 mm wire which is designed to carry full current demanded by the fuel pump, DME, and fuel injectors. I strongly recommend using terminal 30 instead of terminal 86 to supply power via the jumper.
The emergency jumper consists of three leads with male spade connector on each lead (shown below).


Emergency Jumper
To start the car using the emergency jumper, install the jumper in the following sequence:
Install one spade connector into terminal 87.
Install the second spade connector into terminal 87b.
Install the last spade connector into terminal 30. When the connector is installed into terminal 30 you should hear the fuel pump energize. The car can then be started using the ignition switch.

[guru944]

Check ground on engine and especially engine injector harness. Run a gnd wire from intake manifold to strutmount chassis bolt any 1 of 4 available. All our vehicles have a floating gnd issue on the engine/harness.
Use a dmm to check voltages on engine from batt (-) terminal. It should read 0.001v dc. terminal
Keep us posted, later.