VetteC5RFrEak

First and foremost, I appreciate any and all help that anyone can provide. Secondly, please stick it out and finish reading the entire post, I know its long, sorry.

I was given a 1985.5 944 N/A months and months ago. The only issue was that is needed a clutch. Months and months later I finished the clutch job haha. I discovered the timing belt and balance shafts belt was loose and the radiator was leaking. I replaced both belts and installed a new radiator. I finally got the car running and took it down to get it smogged. She BARELY passed by like 4-5 NOx at 25. So finally I had a legal 944 and was stoked to drive the car.

I have a daily commute of 150+ miles and decided to take the car to work. It drove great to work and back the first day. The second day I was on my way to work. I was about 2/3 the way there when I noticed the engine started surging but then it was fine. Few miles later it started again then cleared itself up. I figured I'd get it to work then deal with it after my shift. Few more miles later she completely died out. I then had the car towed all the way back home.

I had been referred to Clarks garage in the past and it was my first place to check out for diagnostic information. I checked the screw on the rotor, it was tight. I checked resistances on the speed and reference sensors, they spec'd out. Their pigtail connectors were broke because I accidentally broke them while doing the clutch job. But they worked so I never thought anything more about them. I checked for spark and wasn't getting any spark. I checked the resistances on the coil, all checked out. I even did the test of manually firing the coil and it produced a spark. I rented a fuel pressure tested, however it didnt fit the fitting on the porsche. I can however smell fuel at the tail pipe while attempting to start the car. I know even though fuel may be getting into the combustion chamber, it may not be adequate if the fuel pressure isn't correct. But considering I'm not getting spark, I'm not to concerned with proper fuel pressure at the current time.

At this point I decided I would try the local junk yard and grab the reference and speed sensors off the car. Unfortunately they were already gone. I then discovered that BMW used the same sensors in a few of their models. So I grabbed two from a BMW there. Got the sensors back home and installed them. Car still cranked but no start. I checked resistances and everything was still within spec except for one of the BMW sensors. So I swapped it with one of the original porsche sensors. The car fired up. I went for a test drive up and down the street and it began cutting in and out again. I even completely lost the brakes at one point; but pumping the pedal brought them back. It stalled a few times but I was able to get it to fire back up. I figured it was the sensors. So I ordered 2 new BMW ones and waited for them to arrive.

I installed the new sensors and the car started right up. I figured all was good (except for the brake issue I still had to diagnose). Garbage day came, I had to move the car. It started up, and drove just fine to the parking spot across the street. Few days later I went to move it back and it started up but then started cutting out again and eventually died. I started it back up and started to move it then it died completely again. This time it wouldn't start back up, and hasn't since.

Since then I have rechecked the resistances on the sensors. They check out. I do not have access to an oscilliscope (sp?) to check their signal. My tach isn't exactly reliable to see if its picking up signal or not since the tach would sometimes not even working while driving. But a slap on the dash and it would start working again. I've checked continuity from the sensors to the DME and no broken wires. I attempted to adjust the sensors, but I was unable to get the drivers side bolt to loosen and bailed on the process. I don't see how they would go out of adjustment just from driving the car a couple hundred miles anyways.

My g/f's dad provided me with an email that was copied from a post on a forum; it could've very well been this forum. In the post it states to check for 12v at pin 4 on the dme while cranking. I only get 10.3-10.5v with a battery putting out a full 12v+. I pulled the ignition switch out thinking maybe it was bad. Everything is fine with the switch. I even manually ran a wire from pin 30 to pin 50. Pin 30 was showing 12v+ and I'm still only getting 10.3-10.5v at pin 4 on the dme. I then discovered the remnants of a aftermarket security system that was tied into the ignition switch. I removed it and reconnected all the wires properly and again checked voltage. I still only get 10.3-10.5v at pin 4.

If you've managed to read this far, I am completely stumped where to go from here. There have been other tests and things I've checked and rechecked during this process, I just simply can't remember them all off the top of my head. Is there something I'm overlooking or over complicating? The engine cranks over nice and strong, no issues there. The belts are still intact. I just can't get the DME to fire off the coil and produce spark to the cylinders.

Forgot to mention, I even opened the DME and looked for broken solder joints and could find none.

Thank you,
- Chris

Travis - sflraver

Check the DME relay and/or Remove, clean, reinstall the main engine ground at the bellhousing. That would be my next step(s).

VetteC5RFrEak

I have done the Dme relay jumper and I can feel the fuel pulsing through the fuel rail but still get no spark. I will try the engine ground as you suggested. Thanks.

azbanks

I just replaced my coil. It was causing similar issues to the ones you are describing. No issues after I replaced it.

VetteC5RFrEak

I did grab the coil off the 944 at the junk yard. It spec'd out too. And still same issue.

Btw, your white cabrio is sexy!

Fara

I would actually, further to Travis's suggestion, do a clean and service on all the grounds in the car. There's plenty of maps on this forum as to where to find them all.

The DME relay was my first thought for this issue. No-spark is a pretty easy give-away.

In relation to your fault with the Tacho - Pull your cluster and clean the big football on the back of your tach. it should start working again properly after doing that. It's not too much of a job and clarks-garage has a full work through. This will allow you to accurately see if you have the tach jump when the ignition is turned over.

I doubt the issue you are having is with the reference sensors, but if you do want to be sure, you can get a wire harness for just the reference and speed sensors online for not much money (I can't remember the supplier - I came across it a few days ago but I have the memory of a Goldfish)

xsboost90

there are two contacts in the DME relay- one for the spark, one for fuel. If only one contact is not making correctly it could cause issues- Get a dme relay, even if thats not the issue its good to have a spare.

Martin

First try unplugging one injector and see if it starts, if so your fuel pressure regulator has failed high and you will need a new one, check for +12v at the coil, also check the wiring loom between the coil negative and dme, it is near the exhaust and can fail.
The fuel pressure regulator is the most likely cause
Good luck
Martin Taylor

LuigiVampa

If not for the fuel in the exhaust I would say fuel filter but it sounds like something else. But do yourself a favor and replace the fuel filter as well. It tends to make for some weird problems sometimes if it is getting clogged.

ZR8ED

To test fuel pressure don't worry about the fitting. Just jamb a rubber fuel line over the threads and use a simple wormgear clamp. Put the pressure guage on the other end of the rubber hose. (I bought a tester and no fittings worked. It did however come with lengths of fuel hose. Works just fine)

JohnKoaWood

Rotor button inside the distributor.. I bet the screw securing it backed out and the rotor button moved!

V2Rocket

Got a spare DME?

VetteC5RFrEak

Whoa, wasn't expecting so many responses so quickly, but thank you!

Fara, I plan to check the grounds as Travis suggested as soon as I get back to the car. And ill pull the cluster and clean it as suggested.

Xsboost90, yea I know the Dme relay has two functions to it, but using the jumper detailed on Clark's garage isn't it supposed to basically simulate that the relay is working? Cause I've tried that and it still won't start. Either way, I do have a new relay coming in the mail.

Martin, I need spark first otherwise disconnecting an injector wont do anything for me at the moment. If I finally get spark and it still wont start then I will try disconnecting an injector. I know I have battery voltage at the coil. Ill check the wiring near the exhaust manifold to ensure its intact.

Luigivampa, ill put the fuel filter on the to do list, thanks.

Zr8ed, ill try that out when I get a hold of the fuel pressure tester again.

Johnkoawood, its tight. That's the first thing I checked since I had read they can back themselves loose. I wasn't so lucky. I'm not even getting spark outta the coil at this point.


V2rocket, I wish I had a spare. The 944 at the junk yard was an, 84. I woulda grabbed its Dme but I knew things had been changed in '85.5.

Again, thanks for the help. I have a few leads to test out when I get home.

V2Rocket

Where are you located? Chances are a RLer is nearby that might have parts to try.

kinda5150

this is a long shot, but have tried wiggling the sp/ref sensor wires? the connectors themselves and wiring leading to them (from the dme side) tend to cause problems. wiggle one at a time and try to start to narrow down which one is causing the problem. good luck.