Consistent no start issue.
 

Last weekend I drove up to Road Atlanta. Roughly a 300 mile round trip excursion. I got home, shut the engine off, and then decided to pull the car in the garage. But it wouldn't start up! At first I thought it was flooded, but after pulling a plug it was dry. After some time it started up and I was able to move it.

Here's the situation, dead cold the car will start. I have ran it for about 25 minutes and it runs fine. When you shut it off, and try to restart it will only turn over. I have NO tach bounce when it doesn't run, but does when it does.

This is what I've done so far. I bought a new speed/reference sensor, assuming they both wouldn't go out at the same time. I tried it on both with no change. I pulled the DME relay and inspected the solder joints, one was cracked, which I repaired. I also pulled the computer to inspect for bad joints. It all looked fine. I pulled the fuse panel to possibly look for a loose connection behind the DME relay plug, which does seem to be working properly. I even tried another one with no change.

I know it's hard to diagnose over the net, but anyone have an idea as the issue? Something I'm overlooking? I haven't checked for continuity, but I wonder would it be that if it's so dang consistent?

Thanks,

Btw, the car won't even restart if you immediately shut it off.

Can you hear the fuel pump turning on?
Are you getting tach display on the dash gauges?
Battery cable seated on battery?

The tach will bounce when it starts, but doesn't when it only turns over. It's not firing when it's not starting. Also, I think I can hear the pump, but I won't know until a friend of mine comes later this week to give me a hand. I checked my connections yesterday, they are tight and clean.

I'm wondering if both my new and old sensor are bad, because I'm not getting anywhere the amount of resistance is should be getting. I first though it might be my meter, but now I'm not sure. For example, I'm reading OL across pins 25&78, and across 8&23.

Assuming you are checking the sensor readings at trhe DME, how are the sensor connections at the firewall?
Also, pull your DME relay again and put in the 3 wire jumper. Yours are the classic symptoms for a bad DME relay. Fails when warmed up.

Good luck,
Jon

Do you have a factory alarm? That has caused similar issues on two of my cars.

Also, check all ground points for safety.

Do you have a factory alarm? That has caused similar issues on two of my cars.

Also, check all ground points for safety.

Fortunely, mine is a non alarm car. As for the relay I replaced it with a new one. Which didn't change a thing. The thing that gets me is it will not restart even if it's only run for a second. Is it possible for the ignition switch to be bad? I know they give problems on these cars.

Also, the wires going to the sensors look good, but I plan to check them at the DME this afternoon. Just to rule out a broken wire.

Look for something simple as well. I spent 4 days on a no-start issue. Even though all of the stuff usually associated with a no-start problem were new, I still ran down the check list over and over again. Wore out my starter too! Turns out the little tiny screw holding the rotor to the crank adapter was missing. I even put the camshaft at TDC and didn't see that the rotor wasn't pointing at the number one spark plug wire. When I first pulled the cap, the rotor screw was at the bottom and I didn't see it missing. The bolt holding the adapter to the cam was in plain sight and that's all I saw. Grrrrr.

Thanks for the suggestion. I looked at that this afternoon, since I recently replaced the timing belt it would be possible that screw could be left loose. Unfortunately, it wasn't the problem.

Sorry I just realized I never specified my car! An 84 944. Yes I'm that guy!

So the consistent no start has come more inconsistent. I've done all the testing I know to do. It's a matter of throwing parts on it to see if that'll do the trick. I've got an ignition switch and a good quality DME relay coming as my spare was a junky URO anyway.

So after two relays, one new speed/reference sensor, and an ignition switch. I found the problem of not starting has to do with the plug going into the ignition switch. Either the plug, or the wiring about two inches away from it will cause it to not start if it's twisted a certain way. I'm not yet sure which wire controls the DME, but I plan to study the diagrams this weekend to find out.

I know it's been a while, but the problem WASN'T in the wiring. It turned out to be a bad DME. After my last post, the car got worse and worse about not starting. To the point of not running at all. I began the task of pulling the dash, but looking at the wiring and doing all the continuity tests I could think of. And, after searching and asking questions from a number of reasources I finally came to the conclusion the DME was at fault. Through all this I wanted to do everything from cuss my car to burn it, but in the end I met some great people and gained a good bit of knowledge about my car!