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The engine in my '88 944 Turbo S died while driving. In the beginning, I felt that the throttle was totally unresponsive while the car was happily running downhill. I then pressed the clutch and saw that the engine was at 0 rpm. To give some context: I had been driving for about 80 miles including hard driving on some canyons and the car worked flawlessly. Stopped for about an hour for breakfast, started the car again without issues and just after about a mile of driving downhill I accelerated hard to overtake a van and the engine died.
The engine is stock and seems to crank normally but does not start. Had a check at the DME relay and it's working fine.
What else could I check? Has anyone had this kind of problem before?
Lots and LOTS of people have that problem with these cars. They're all 30+ years old, so it's to be expected. How did you check the DME relay? There's a way to bypass it on Clark's. Could also be a fuse, speed or reference sensor, fuel pump, fuel system blockage in the tank.
It's the first engine that does not start that I have to diagnose myself and I'm a bit lost. Any suggestion at what to look at that doesn't require specialized tools?
Had a similar issue with my 88 n/a and it ended up being the DME itself. My problem was intermittent and the car would lose power and shutoff moments after I noticed the loss of power. An issue like this, you're going to have to start somewhere and go through all the different tests. If you've already verified the DME relay is good, my next step would be to bypass the DME relay to verify the fuel pump is working. If the pump is good, I would then move onto checking spark. It would help too if you could get your hands on a spare DME that way you could swap it and see what she does. As noted above, I'm an n/a guy so I'm not familiar with the exact engine differences of a turbo engine, just wanted to put some thoughts out there, I know how disheartening it is to have this issue. Good luck and give as much detail as you can with your follow up posts.
When cranking, does the tachometer slightly bounce? If no, you probably have reference sensor issues (likely wiring) or DME/ECU problem. If yes, jumper DME Relay slots in fuse box and listen for fuel pump.
If it was running really well as you say, it's probably something catastrophic like total loss of some electrical connection or major part failure (as opposed to bad spark plugs or wires)
If you can get a 12v LED, it will prove very helpful in testing many things like coil, injector plugs, more. Also check out Tom's new reference sensor tester ("Carmonica").
Welcome to the "drives great then dies" world of old car wire, rubber, plastic, and paper
I had this on my '89 951 and it was the DME itself. Very frustrating, as it was intermittent and took a long time to diagnose. We thought it was easier / cheaper stuff first. Car would just shut off randomly.
Here are some pics of my "cracked solder joints" on the DME/ECU... however, with my cracks, the car did start eventually like within 10 mins of stalling.. then randomly die again while driving two days later.. and so on
These did not look like breaks nor were they loose in any way; indeed, they were barely visible to the eye. Yet heating them with a soldering iron and adding a touch of new solder solved my random stalling. Oh, the joy!
I just went through this after doing a reseal, etc. my cause was simple, a connector at the temp sensor wasn’t fully connected. Fired right up once connect d. Search Rennlist for “No start”...you will find a series of tests to eliminate potential causes. In my case, I had fuel, spark and air.
Find my no start thread and I rec’d lots of great suggestions and if you follow those you’ll likely find your issue. Guys on this forum are awesome and knowledgeable. You’ll be happy to know you’ll not be the first to troubleshoot a “No start”. Good luck and the more info you can provide on your situation the higher quality suggestions you’ll get.
When cranking, does the tachometer slightly bounce?
Interestingly, with the DME relay connected, the tachometer does not bounce but if I disconnect the DME relay the tachometer does bounce. Is this looking like a faulty DME?
Search for ECU Doctors video on testing reference and speed sensor at the DME harness for both impedance and voltage. If they test fine, you’ll know that both your sensors and harness are good, ruling them out.
Search for ECU Doctors video on testing reference and speed sensor at the DME harness for both impedance and voltage. If they test fine, you’ll know that both your sensors and harness are good, ruling them out.
Warning! My sensors passed these tests from that very same video and it turned out one of them was bad. It was a brand new FAE sensor and the construction allowed for the shield to have continuity with one of the pins; the ECU shut down the signal *after* the point where it's measured in the video.
It took an oscilloscope to offer a clue (one sensor's sine wave was not showing fully below the x-axis)
Short of Tom's excellent new "Carmonica" ref sensor diagnosis tool, you can either borrow an oscilloscope or swap in another ECU. These are the only three methods diagnosis methods I personally would count on.
Interestingly, with the DME relay connected, the tachometer does not bounce but if I disconnect the DME relay the tachometer does bounce. Is this looking like a faulty DME?
try a noid light in the injectors and see if they are blinking, measure the fuel pressure at the end of the rail should be around 35. Check for a spark at the plugs, check the intake boot to see if it is tight make sure power is going out on fuse 34 in the crank position
- DME relay ok
- Fuel pump fuse ok
- Speed/reference sensors ok according to ECU Doctors resistance and cranking voltage tests
- Spark plug testing light indicates that there is spark
I'm going to buy a fuel pressure gauge but I don't have it yet. Is there any other test I could run without specialised equipment?
Originally Posted by Seattle 993
Search for ECU Doctors video on testing reference and speed sensor at the DME harness for both impedance and voltage. If they test fine, you’ll know that both your sensors and harness are good, ruling them out.
I've just run the tests and it has passed them: both speed and reference sensors measured at about 1 kilo ohm. AC voltage tests when cranking are also OK: more than 1 V for the speed sensor and less than 1 V for the reference sensor.
Warning! My sensors passed these tests from that very same video and it turned out one of them was bad. It was a brand new FAE sensor and the construction allowed for the shield to have continuity with one of the pins; the ECU shut down the signal *after* the point where it's measured in the video.
My sensors have been in the car for a long time. Could they have gone bad and yet still pass the ECU Doctors tests?
09-21-2019, 10:42 PM
951 Engine died while driving
