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Strange 944 Running/ No Start Issues....

 
Old 04-20-2019, 04:20 PM
  #301  
Jacob AbuKhader
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Originally Posted by Dan Martinic View Post
How many thirty-plus year old DMEs does it take to fix a voodoo running issue?

One. A good one. LOL

Broken multi-meter? That's a new one.. never think to check if they're working properly or not. Good luck and I hope that's a wrap on this!
Lol you and me both! 👍🏻
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Old 04-29-2019, 07:25 PM
  #302  
Max Miller
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well I just spent the past few hours carefully reading thru this entire thread, what a roller coaster. I have recently bought a 1983 944 with the same symptoms you have been chasing. The car fires up with a misfire and blowing raw fuel smoke out of the pipe. The car will run for a few minutes until it dies, then will not start up. One day last week the car started up and cleared up and ran like a top for 10 minutes, then died SUDDENLY with no warning signs, then would not restart. the next day the car restarted with the smoke and misfire.
here is a list of things the previous owner replaced. temp sensor, crank sensor, j boot, air filter, cap rotor wires, plugs, injectors, dme relay.

I found that the car was over fueling to the point that the oil was full of fuel, to the point that oil was being sucked into the intake. i changed the oil and the fouled spark plugs, the fuel pressure regulator, cleaned out the air box. no change

I installed a fuel pressure gauge directly to the end of the fuel rail. I went thru the pressure and pressure leak down test on Clarks-Garage. all the values were dead on. I found a set of new re manufactured injectors hopeing that would solve the problem. I have checked the compression several times, the spark, checked for voltage at the injector connectors. I have swapped both the relays I have back and forth. the plugs keep fouling and the car continues to misfire and run rich.

What i will try next- the relay jumper- Check the positive terminals at the battery- unplug the AFM- unplug the coolant sensor- try the combination of the injectors plugged/unplugged. These are some of the quick things i can try before getting down to business. looking for a systematic approach to try to work thru this. I will inspect the dme relay and the ]ECU right away if you guys think i should start from there. I honestly dont know which way to go after reading thru this whole thread.


I hope one of you guys will take some interest and mercy on my situation like you did for Jake. I have decent troubleshooting abilities, as i have been fixing bikes and cars for 10 years. I have a garage set up with all the tools i should need to get thru this, hopefully with a little support. thanks guys.
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Old 04-29-2019, 07:34 PM
  #303  
Jacob AbuKhader
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Originally Posted by Max Miller View Post
well I just spent the past few hours carefully reading thru this entire thread, what a roller coaster. I have recently bought a 1983 944 with the same symptoms you have been chasing. The car fires up with a misfire and blowing raw fuel smoke out of the pipe. The car will run for a few minutes until it dies, then will not start up. One day last week the car started up and cleared up and ran like a top for 10 minutes, then died SUDDENLY with no warning signs, then would not restart. the next day the car restarted with the smoke and misfire.
here is a list of things the previous owner replaced. temp sensor, crank sensor, j boot, air filter, cap rotor wires, plugs, injectors, dme relay.

I found that the car was over fueling to the point that the oil was full of fuel, to the point that oil was being sucked into the intake. i changed the oil and the fouled spark plugs, the fuel pressure regulator, cleaned out the air box. no change

I installed a fuel pressure gauge directly to the end of the fuel rail. I went thru the pressure and pressure leak down test on Clarks-Garage. all the values were dead on. I found a set of new re manufactured injectors hopeing that would solve the problem. I have checked the compression several times, the spark, checked for voltage at the injector connectors. I have swapped both the relays I have back and forth. the plugs keep fouling and the car continues to misfire and run rich.

What i will try next- the relay jumper- Check the positive terminals at the battery- unplug the AFM- unplug the coolant sensor- try the combination of the injectors plugged/unplugged. These are some of the quick things i can try before getting down to business. looking for a systematic approach to try to work thru this. I will inspect the dme relay and the ]ECU right away if you guys think i should start from there. I honestly dont know which way to go after reading thru this whole thread.


I hope one of you guys will take some interest and mercy on my situation like you did for Jake. I have decent troubleshooting abilities, as i have been fixing bikes and cars for 10 years. I have a garage set up with all the tools i should need to get thru this, hopefully with a little support. thanks guys.
My advice to you is to CAREFULLY check all of the wiring. Peanut and Dan as well as many others listed a lot of different testing methods to help me diagnose. Read this thread and read my old one to see what they suggested and the tests I conducted to see if yours follows the same path.

Compression is great

Fuel pressure within spec? Great!

Check for 12v at the pump while cranking.

If you get the car running throw a meter on the pump and let it run and see if it dies. Isolate between an electrical issue or a mechanical issue. Yours sounds electrical to me but again donĺt make any assumptions and keep testing!

Use clarks to test every single sensor in the engine or at least as many as you can. Look for correct voltages and continuity where it should be.


If you have fuel air spark AND all of your sensors check out and your fuel pump is not the issue, I would start the long arduous search for a reliable ECU. Keep in mind I had to go through like 3 of them and all the while I kept doubting myself.

Good luck!
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Old 04-29-2019, 09:10 PM
  #304  
Dan Martinic
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Originally Posted by Jacob AbuKhader View Post
If you have fuel air spark AND all of your sensors check out and your fuel pump is not the issue, I would start the long arduous search for a reliable ECU. Keep in mind I had to go through like 3 of them and all the while I kept doubting myself.

Good luck!
I for one am starting to save up for one of those new FTech9 ECUs. Been thinking about this lately: if simple and robust sensors such as magnetic reference sensors and the like need replacement after so many years, why am I assuming the ECU--full of sensitve chips, old passive parts, solder--is still ok?

Like the AFM, the ECU is a circuit board printed in the 80s and in operation under heat & stress for thirty years. I mean, if you strapped an 80s calculator to the floorboard or the engine and drove 100k+ miles over three decades, would it still work?

I can't believe I'm still relying on my original ECU. It's nuts!
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Old 04-30-2019, 01:30 PM
  #305  
Max Miller
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Default My thoughts after sleeping on it

So if you guys disagree with my conclusions, please take them for face value. After reading thru this thread my thoughts are that Jacobs initial problems he was facing was a deteriorated injector driver circuit on his DME computer. His secondary problem he was facing was a intermittent DME Relay. As he went thru relentless troubleshooting, making adjustments here and there, and disturbing fragile connectors and wiring; he developed a set of issues beyond the initial set of problems. His car ran great for a period of time, and did not develope a cluster of issues simotaniously. His issue concerning the rich mixture and and misfire suddenly curred with a properly functioning DME computer, and his stalling/no start stymptoms cleared with a functioning DME Relay.

These things come to a head to me, and apply directly to my symptoms. My car ran great for the previous owner for years, and suddenly this issues appeared. It's also shows to be internment, as witnessed by myself. Many things were tested and replaced and tried over and over, with no positive move twords a solution.

It's also worth mentioning that the previous owner gave me a box of parts, including a DME computer that came from a verified good running car. I also have a new DME relay on the way. The P/O told me last night that he never got around to installing the DME computer because he was never lead to believe that it could be the root of his problems.

So at this point, before I go any further disturbing my system, which still will start and run every time I let it rest, should my next move be to install this computer and relay?
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Old 04-30-2019, 05:56 PM
  #306  
Dan Martinic
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Originally Posted by Max Miller View Post
So if you guys disagree with my conclusions, please take them for face value. After reading thru this thread my thoughts are that Jacobs initial problems he was facing was a deteriorated injector driver circuit on his DME computer. His secondary problem he was facing was a intermittent DME Relay. As he went thru relentless troubleshooting, making adjustments here and there, and disturbing fragile connectors and wiring; he developed a set of issues beyond the initial set of problems. His car ran great for a period of time, and did not develope a cluster of issues simotaniously. His issue concerning the rich mixture and and misfire suddenly curred with a properly functioning DME computer, and his stalling/no start stymptoms cleared with a functioning DME Relay.

These things come to a head to me, and apply directly to my symptoms. My car ran great for the previous owner for years, and suddenly this issues appeared. It's also shows to be internment, as witnessed by myself. Many things were tested and replaced and tried over and over, with no positive move twords a solution.

It's also worth mentioning that the previous owner gave me a box of parts, including a DME computer that came from a verified good running car. I also have a new DME relay on the way. The P/O told me last night that he never got around to installing the DME computer because he was never lead to believe that it could be the root of his problems.

So at this point, before I go any further disturbing my system, which still will start and run every time I let it rest, should my next move be to install this computer and relay?
There is not much to disturb with the relay; just be sure to check that the female receptacle ends are still in the box socket

I forget if yours is early or late but regardless disconnecting ECU/DME always makes me weary of that old stiff loom of wires I'm moving.

However, when you see how microscopic lines and cracks in the solder joints can disable the unit, as happened to me, you realize that even moving the ECU around--bumping it hear or there--might cause an issue with it
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Old 04-30-2019, 06:52 PM
  #307  
Max Miller
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Okay I follow what your saying. It may be worthwhile for me to do thorough inspection of my secondary ECU before installation. I'm handy with an iron and have reflowed solder joints on many PCB boards for audio equipment and other circuit boards. I have my first gets crossed at this point. If I don't get the results in hoping for a will begin from square one with testing sensors and continuity and the other finer points
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Old 04-30-2019, 08:24 PM
  #308  
Max Miller
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Hey I wanted to let you guys know I swapped the DME and the car ran flawlessly. I was able to drive it around for the first time. The car began smoking a bit after a couple laps around my shop, I didn't have time to investigate. I'll fill you guys in with more info later. Thanks
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