No start Porsche 944 Turbo

[951Porsche]

Hi Folks,

I have a 944 turbo that seems to be getting the better of me. I have no spark or fuel. I have replaced the reference sensors and the dme relay and even double checked them in a working car. These parts are definitely working. I have tested the 15 feed to dme relay and it has 12v when ignition is switched on. I also have ground and the 12v 30 feed. If I inset the jumper wire the pump runs and I get a very very weak spark (almost static!). The injectors fire. I took off the relay and the fuel sprays the exact same as it does on my running car that I have parked next to the turbo and have been using to double check everything. So to recap... with the three part jumper wire in place the injectors spray, fuel pump pumps and I get a tiny, weak spark ( plug is well grounded!). The car has 2 ecus, the main and the one that has oil going into it? The car is not fitted with an immobiliser. Any help or advice would be greatly appreciated. I am willing to try any suggestions, post videos etc, and am not the sort of person who will not post to say when its resolved! That drives me mad!

[DannoXYZ]

The KLR computer should NOT have oil going to it. Remove the MAP-sensor hose and clear out the oil.

Other than that, try:

1. swapping speed/ref sensor connectors? Easy to mix them up as the harness connectors are the same.

2. checked the speed/ref sensor signals with an oscilloscope? Should look the like the following:


Without these signals exactly as shown, the DME computer is blind is won't do anything with fuel or spark.

[kdjones2000]

Have you checked your coil is working?

[TrailRider]

^^ both good things to check above.

When cranking the car, do you have slight tach bounce? It'll be about 1/16th to 1/8th of an inch bounce for each crank. If not the speed and reference signals are not getting to the DME.

I had a problem with the wiring to the DME before and replaced the lines with the Lindsay Racing reference sensor replacement wires.

[951Porsche]

Firstly I would like to say a huge thank you for your responses. I really appreciate them. I don't have an oscilloscope but I will try buy one on ebay later. I put on a spare coil a week ago but to be sure I will put on the one from my working car. It is strange that the fuel pump doesnt activate without the jumper wires. The tach jump once to over the 1000 rev then drops fully and doesnt jump again. Then if I stop the engine and turn it again immediately it will give one small jump and then nothing... The sensors are good so I will check the loom. I swapped the sensor plugs and didnt get any jump.

[951Porsche]

Just checking... would this oscilloscope measure the pulse?

New Mini AVR DSO150 Digital Storage mini pocket Oscilloscope With USB Cable agz | eBay

[TrailRider]

You don't ~have~ to buy and oscilloscope.

Follow the steps here via this video with a volt meter -

https://www.youtube.com/watch?v=zeFOOcLSk60

This will show you if the signal from both sensors are getting to the DME. If you aren't getting it, then the wiring harness may be to blame if you know that both sensors are new / good.

[951Porsche]

Thank you so much! I have borrows one now...



I'll try the oscilloscope and should I not manage to work it will definitely use that multimeter one. I really appreciate all the help.

[951Porsche]

Originally Posted by DannoXYZ

The KLR computer should NOT have oil going to it. Remove the MAP-sensor hose and clear out the oil.

Other than that, try:

1. swapping speed/ref sensor connectors? Easy to mix them up as the harness connectors are the same.

2. checked the speed/ref sensor signals with an oscilloscope? Should look the like the following:


Without these signals exactly as shown, the DME computer is blind is won't do anything with fuel or spark.

Hi DannoXYZ,

Thanks for your help. You were right sorry... It looked like oil but the tube is just slightly yellow! I managed to borrow an oscilloscope. The speed sensor pin 27 and 8 on dme connector was exactly as your drawing showed. The reference sensor pin 25 and 26 was as follows:




(sorry this isn't exact... I tried to use microsoft paint to draw it as best I could.)

[DannoXYZ]

Ah, you can connect the oscilloscope to laptop and download the waveforms.
Or you can take a snapshot with phone-camera.

The important data to examine is ref-signal should start on a positive slope and have peak of at least 2.0v. And the speed-signal should have peak-to-peak of greater than 2.5v total.

The gap of the sensors to the flywheel determines the voltage. There's some spacers under the sensors that allow adjusting this gap. The trigger-bolt for the ref-sensor is also adjustable with an allen-key.

[951Porsche]

Hi, Thank you for that! I was starting to assume if it looked close to right I was safe! I will put in a few hours on it tomorrow and let you know the colt of it. Thank you very much.

[951Porsche]

So an update... I have replaced the coil with a sports coil from my car that works and still no spark. With the jumper in place the car pumps fuel and the injectors spray when I swing the engine. Having finally worked out the oscilloscope test my reference sensors are working and that is testing them at the dme connector which I assume means the wiring between the two is good...

I'm thinking that maybe its time I look at the dme relay and try to get this working first?

What I know...

The DME relay is definitely good.
The ECU and KLR is definitely good.
The sensors are good.
I have 12v at the dme relay on pins 30.
I have 12v at the DME relay at pin 15 when the ignition is turned on.


Now Im coonfused as to why the relay does not pump when these three are present yet the jumper does?

Does anybody know how I could test the 85b ground from dme to pickup pump?
what the pickup pump is and does?
how I check ground via the DME?

I would really appreciate any advice.

Thank you

[kdjones2000]

If you have no spark that can be due to several things:

1) Speed/Reference sensor or connections

2) Coil is bad

3) DME is bad

4) KLR is bad

5) Rotor / Cap are bad/not turning

6) Your alarm module has died

If you are getting injector pulse and fuel while cranking, with the jumper of the DME relay, then your sensors are fine. I assume that the jumper you made was a "Y" type, which powers both the DME and the Fuel Pump. Correct? The car should have started and run with that setup.

Have you checked for spark AT THE COIL? If there is no spark at the coil, then I'll bet 10 cents that your DME is kaput.

You say that 1 through 3 have been checked and are known good. That leaves #4, 5 and 6. You can jumper out the alarm and even the KLR to test things.

I would also find a "DME Test Plan" (online or elsewhere) and have a look at that. It goes through possible troubleshooting for you. Clark's Garage also has no start troubleshooting recommendations. HINT: I saw it recently on the Arnworx web site...

[nynor]

i like 6.

[951Porsche]

Originally Posted by kdjones2000

If you are getting injector pulse and fuel while cranking, with the jumper of the DME relay, then your sensors are fine.

This is excellent!

The DME ecu is definitely good as is the klr because I have tested them in my other 944 turbo.

I will check the spark at my coil next and see. I'll check out that clarkes website and try the troubleshooting as it might explain why my dme relay doesn't click in....

[951Porsche]

And it starts!!! Today I took out the plugs and tested the spark with the actual sparkplugs that are in the cylinder and there was no spark. tried an old plug and there was... I went and bought four plugs and tried to start it.... nothing! The I got 'easy start' and sprayed it into the throttle and when my friend turned the key it started and cut out. Then I put in the jumper instead of the relay and used the starter fluid again and it started and ran!! I stopped and started it warm no problem.... then left it and came back and it wont start!

[kdjones2000]

Time for new DME relay, sounds like.

Now you get the fun of chasing an intermittent issue. Sensors/Connectors and DME are possible culprits, among other possibilities.

[951Porsche]

So today was interesting.... I sprayed easy start in... fired the car up.... I then sprayed easy start on the air hoses on the engine and the engine picked up when I sprayed it under the air intake manifold as you look in from the right hand side.... I then removed a cracked air hose and replaced it but the car still didnt start cold i swapped the reference sensors, dme and dme relay with my good turbo and it drives perfect and starts perfect with them....

[DannoXYZ]

so you've narrowed it down to:

- speed sensor
- ref sensor
- dme relay
- dme

is the other Turbo working with these components from the non-starting car?
You can swap tem back one at a time to narrow it down to a specific component.

[951Porsche]

Ok and Its sorted!! I missed another vaccuum leak! The big corner rubber pipe that goes into the maf meter had a crack in it! For the moment I have sealed it with a type of tiger seal! And now she is running perfect! Guys thank you so so much for all the help!