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Strange 944 Running/ No Start Issues....

 
Old 11-20-2018, 11:42 PM
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Jacob AbuKhader
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Default Strange 944 Running/ No Start Issues....

Hi everyone, starting a new thread to make it easier for everyone trying to help me out with my 944 problem. I've made some headway on solving the problem but keep running into road blocks. Id like to thank everyone for their time and their suggestions both on this thread and on my previous one. Let's dive in.

'83 944 is showing severe signs of over fueling. Smokes horribly (black carbon soot), CO levels off the charts, Fumes eye watering with heavy raw fuel smell. Oil being diluted with gas. Car will sometimes run and drive perfectly or will stall at any given moment without warning. My plugs are carbon fouling left and right. Most of the time my car refuses to start. It will just crank and crank and crank. to avoid flooding I do not step on the gas when trying to start. However if I do the car starts and runs terribly on perhaps 2 or 3 cylinders. Other times the car starts and runs normally until it either develops a misfire or dies completely.

Here is what's strange. During a no start if I remove the fuel pump fuse and kill the pump, the car starts and runs. As soon as I replace the fuse the car dies.
If the car manages to start under normal conditions but runs bad and idles rough, it smoothes out once I disconnect the AFM. If I try connecting the AFM the car stalls and dies.

Here is a complete list of everything I have tested and replaced.

Replaced:
Battery
Battery ground cables
Starter
spark plugs (5 sets in the last 10 months)
Oil (3 changes in the last 10 months)
Fuel Pressure Regulator
Fuel Pump
Fuel Filter
Added in car fuel pressure gauge
Ignition coil
Intake manifold gaskets
Fuel Injectors 3/4 are replacements for my originals. All have been sonically cleaned and flow tested.
AFM replaced with a tested good unit.
Coolant temperature sensor (for DME not gauge)
AOS Seals (car was leaking oil back up through the intake. leak has stopped since replacement.

Test results:
Fuel pressure within spec, 29 psi running, 32 psi car off pump jumpered.
12 volts at the pump when cranking. Zero volts when fuse is removed.
Speed/ Ref Sensors. (ohm output within spec)
Wiring harnesses for injectors, AFM, TPS, Coolant TMP, Speed/ REF sensors, Checked for continuity/ shorts.
TPS tested via clarks procedure.
Timing, all timing marks line up perfectly, belt is in good condition.
Oil Pressure builds when cranking. Normal when running.
Spark, Each plug was removed and grounded to verify spark
Cap and Rotor were inspected, both in good condition.
Grounds checked/ cleaned.

Im not really sure where to go from here, the car is still showing these symptoms. car was my daily driver for 2 years. symptoms showed up in January. All parts replaced one at a time systematically after troubleshooting. others were just preventative maintenance.


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Old 11-21-2018, 10:21 AM
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Dan Martinic
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Hi Jacob! Sorry to see you're still after this one

I'm wondering if your motor is worn out to the point of not sufficient compression? Maybe your "over-fueling" is simply mixture not burning thoroughly. I know.. it's the last thing we'd like to admit possible
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Old 11-21-2018, 12:51 PM
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Originally Posted by Dan Martinic View Post
Hi Jacob! Sorry to see you're still after this one

I'm wondering if your motor is worn out to the point of not sufficient compression? Maybe your "over-fueling" is simply mixture not burning thoroughly. I know.. it's the last thing we'd like to admit possible
Hey Dan, good call on the injectors. Turns out one was leaking, one was spraying too much and 2 werenít spraying enough lol. Iíll see what I can do about getting some compression numbers. I hope thatís not my issue.
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Old 11-21-2018, 05:43 PM
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How do you know the DME is good? A bad temp sensor in the AFM can cause all sorts of grief, even if it works fine in other respects. How about the DME? If you loop checked each circuit, did you also check to insure there are no shorts to grounds, or other circuits? Make NO assumptions.
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Old 11-21-2018, 05:59 PM
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Jacob AbuKhader
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Originally Posted by tempest411 View Post
How do you know the DME is good? A bad temp sensor in the AFM can cause all sorts of grief, even if it works fine in other respects. How about the DME? If you loop checked each circuit, did you also check to insure there are no shorts to grounds, or other circuits? Make NO assumptions.
I have not had a chance to replace the DME yet. Iíve tried searching for ways to test it but there really doesnít seem to be much that I can do short of swapping it with one from another car. When I went around checking for short circuits I conducted the first test with the DME unplugged to verify the harness was good and then I went around again with the DME plugged to see if anything suddenly had a readingbit wasnít supposed to. The only weird thing thatís happening is now one of my relays is opening and closing wildly when the fuel pump fuse is in. When I pull the fuse the relay stops. Thatís very very very new just started happening yesterday. Hereís what Iím referring to.

The fuse for my antenna and radiator fan keeps blowing but some how both of my fans come on. Low speed with the AC **** and High speed when the temp gauge reaches the third bar and shuts back off at the first bar. I have no idea if this is related to my running issue but worth noting my electrical system has gremlins.



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Old 11-21-2018, 06:05 PM
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If someone has a pinout for this that might help. If I’m going based off of the owners manual this is my wiper relay.
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Old 11-27-2018, 09:45 PM
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Is there any way I can repair this without replacing the entire harness? Was wiggling wires the other day with the car running and it died. Could have been coincidence but Iím not sure
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Old 11-28-2018, 09:56 PM
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Alright well I opened up Pandoraís box last night. Hereís a video update for everyone. Too much info to type 😂.

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Old 12-12-2018, 06:58 PM
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Very very strong suspicion this may have been the rich issue all along. I sincerely hope it was. It was mentioned in my previous thread that even if the sensor doesnít fail completely it can still cause running issues.
So... any tips for getting the last half of the bracket out?



Wiring harness is out. Once that bracket is out things can finally start being put back together.
​​​​​​​
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Old 12-12-2018, 10:40 PM
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Recently, I had a weird stalling issue and I fixed it by re-soldering some joints in the DME. Turns out there were cracks enough to mess it up. They just look like little lines. Perhaps you can open up your DME and check for these lines on joints. I found zooming with my iPad's camera made these lines easy to find (or use cell phone camera same thing)







I didn't remove the old solder; I simply heated up joints with my iron and flowed a little bit of fresh solder real quick. Did this for all joints with lines above. I can't believe it solved my problem. Take a look inside your DME
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Old 12-14-2018, 01:21 AM
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Originally Posted by Dan Martinic View Post
Recently, I had a weird stalling issue and I fixed it by re-soldering some joints in the DME. Turns out there were cracks enough to mess it up. They just look like little lines. Perhaps you can open up your DME and check for these lines on joints. I found zooming with my iPad's camera made these lines easy to find (or use cell phone camera same thing)







I didn't remove the old solder; I simply heated up joints with my iron and flowed a little bit of fresh solder real quick. Did this for all joints with lines above. I can't believe it solved my problem. Take a look inside your DME

YOU'RE KIDDING ME... TINY CRACKS LIKE THAT CAUSED A STALLING ISSUE?!

Lol in any case Iím glad you got that resolved! CB looks great! Definitely going to open up my ECU and have a look see... although from the looks of it I suspect itís been opened before... red paint on the screws and they wonít budge an inch. Not sure if thatís supposed to be like that.

Im still struggling with removing the sensor bracket for the speed/ ref sensors... how the hell does anyone get an Allen key in those two bolts???? Only thing beeping me from reinstalling everything.
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Old 12-14-2018, 08:29 AM
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Not kidding; those little lines caused serious stalling! Crazy. The joints weren't loose at all.

Sensor bracket bolts: read this thread and note my solution post #22:

https://rennlist.com/forums/944-turb...cket-bolt.html

Cheers
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Old 12-27-2018, 11:15 PM
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Originally Posted by Dan Martinic View Post
Not kidding; those little lines caused serious stalling! Crazy. The joints weren't loose at all.

Sensor bracket bolts: read this thread and note my solution post #22:

https://rennlist.com/forums/944-turb...cket-bolt.html

Cheers
Dan youíre a genius. I found that removing the starter also helped me free up some room though wasnít neccissary. Unfortunately I still canít get those bolts out. Out of fear of stripping the heads Iíve decided to leave that alone for now until I can get a spare set of hands to help me. I sucsessfullty cut the bracket but didnít know Iíd have to spend $140 on a new one with the shield to prevent kick back. Oh well whatís done is done.

I popped open the ECU and Iím less than pleased. Dirt was entering the seal, and using your method of zooming in with an iPhone camera many of the solder joints donít look in too good shape. A new DME will be on its way shortly.

Second ive got the wiring harness out and have been able to pinpoint exactly what one of the 2 POs of this car as done electronically. It seems the reference sensor had a short, or melted due to heat or decaying wire. Rather than replace the connector or the harness they decided to splice to another ground. So I have 3 wires tied into two grounds involving the O2 sensor, the speed, and the reference sensor. Other than old decrepit heat insulation and some hot spots the harness appears salvageable. I think Iíll just order the replacement harnesses ready to go from Lindsey. Heads up for anyone shopping, you can buy a new one from the Porsche factory for about $350. Not that bad of a price compared to Lindseyís price of $500 for a full harness and $1200 for the turbo guys.

I believe the reference sensor was beginning to fail and along with the frayed wiring, the car would just suddenly not fire correctly or lose a signal altogether. New sensors, an updated harness, and a clean ECU should get my car back on the road. Iíll continue to post progress updates as well as photos. Hope everyone had a good Christmas and Happy holidays. Hereís to a new year of spirited driving and an empty wallet 🥂













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Old 12-28-2018, 01:20 AM
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You can get a new complete NA harness from Porsche for $350? Really?

Looks like you're making good progress on the wiring front. Great work!
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Old 12-30-2018, 09:47 AM
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Originally Posted by Dan Martinic View Post
You can get a new complete NA harness from Porsche for $350? Really?

Looks like you're making good progress on the wiring front. Great work!


Hereís the diagram. This one of of 3 Iíve seen however there are many different part numbers in relation to different harnesses. Havenít been able to isolate what PN corresponds to what specific harness.

Boy do I feel stupid. Service receipt from 2015 just before I bought the car. ďCar runs poor, smoking, plugs black, injectors cloggedĒ.... they rebuilt injectors, new cap new rotor, new plug wires, cleaned the plugs, RR reference sensor BUT NOT THE SPEED SENSOR. I knew it had to be something stupid.
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