944#447

I have spent days reading threads on this. I’m starting to think I have a bad DME.

Short history: It was very very well cared for by the previous owner. 75k mikes. Every receipt kept. All maintenance done as preventative. Car sat the 8 years. I was told it was parked due to failing smog. Then the PO developed health problems.

In the last 2 weeks I drained the tank pulled the strainer and flushed it. Flushed the lines. Replaced the strainer with a new one, new line to pump, new pump, new fuel filter, sent injectors off to be rebuilt and flow rated. I pulled a vacuum on the FPD and FPR for hours and it held. All parts OE.

When draining the oil almost 3 gallons of fuel and oil came out, it’s been sitting that way since it came into my possession, I had it trailered into my garage from the previous owners. I never even cranked it. Replaced with 20w50 and a Mann filter.

Spark plugs fouled beyond anything I’ve ever seen. I put in new ones.

I was so surprised, everything looks so clean on this car, it obviously is having some electrical issues and was parked for that reason.

When investigating the log of records I discovered the 2 new catalytic converters and O2 sensors in the last 5 years it was on the road and 5000 miles (2008-2013ish), before being taken to Porsche for a diagnosis to replace the catalytic converter again. Then it was parked.

It is over fueling so much to the point of me being able to pull the fuel pump pressure and it suddenly runs better until it dies. (I drained the fuel line again from the rail and while cranking to get the pump to purge the line it actually fired and ran.

I really want it to be a bad DME but I just don’t know where to go from here.

thank you for your time and assistance
​​​​​​-Adam

931guru

If you suspect the ECU/DME, remove your ECU and take it to another 83 to 85/1 944 and install it to see if the symptom follows the part.

Also, you want to check the bosch part number on the body of the injectors. There are early and there are late injectors that look almost identical.

You should not have a problem finding another early 944, if you belong to the Porsche Club of America... You do belong to PCA, don't you?

If all else fails, contact Tim Comeau at Comeau Racing in San Diego. He should be able to help.

walfreyydo

First thing I would do is test the fuel pressure, the actual measurement of the fuel pressure, not just "we have pressure". A pressure test kit can be had for $20 on amazon, although youll also need a metric to standard adapter to connect it to the fuel rail, a M16x1.5 to 3/8" I believe (double check this). If the pressure tests out good (seek out Clarks Garage for fuel pressure specs), then next step is to test injector pulse (requires a noid light kit, $25 on amazon). This will tell you if the DME is sending the correct signals/injector pulses. If the pulses are coming out ok (and not sending a constant signal to the injector), I would then send out the injectors for testing and cleaning. Google witch hunter. Old injectors can become stuck open, and with their age, its not a bad idea to get them refurbished anyways. It also wouldn't hurt to test the AFM and DME temp sensor (or replace the temp sensor, they are cheap), although its unlikely that these would cause that amount of over fueling, still worth a check.

If still over fueling after all that then I would swap out the DME as guru mentioned. My personal opinion is that yes, DME's can go bad, but its worth checking all the other potential issues first before going down that road because 1) DME's are expensive, and 2) finding one to swap is hard (although being in SoCal means you are close to Comeau, lucky for you). The added benefit of the noid light test is that it will also give you an indication if there is an issue with the DME and the pulses its sending to the injectors (ie: constant signal/pulse would indicate an issue with DME or wiring).

Note: one reason you may have found so much gas in the oil is if the car was turned over repeatedly without spark. This could be from someone continually trying to start the car without pulling the fuel pump fuse, thereby spraying fuel into the combustion chambers and having it leak past the rings into the oil pan below. So just because you have a ton of fuel in the oil doesnt mean its running rich or have an issue with DME/injectors... However it does seem that with the repeatedly fouled catalytic converters in the history of the car, that there is indeed an issue with over fueling. Just flagging here that we shouldn't make the assumption simply from the gas mixed with oil (not saying you are).

Injector pulse test:

Fuel pressure test:

Jfrahm

I agree, the DME temp sensor and a leaking FPR or damper are the top reasons for this issue. IMO the temp sender can flood out the car when misbehaving.

It's good that the FPR and damper hold vacuum but I'd test them under pressure anyway, ideally using a DME relay jumper and seeing if they push any fuel out the vacuum port with the pump running.
For the DME temp sensor if it tests OK at the sensor you want to check the reading at the DME as well in case of a wiring issue.

944#447

I could really use a lead for a test and repair manual.

Id like to test the temp sensor but I need the procedure.

I ordered a FPR and temp sensor, the blue injector type connector under the intake. It’s not very expensive.

I contacted Comeau racing in San Diego he advised me to noid light the injectors and put a pressure gauge on the rail. Somewhat difficult to do alone; crank the car and check injector pulses. I suppose I can solder and wire up some inline jumpers to my old oscilloscope and look at it on the floor next to me while I crank but that will take some time to set up.

Any links to a 944 thread on fuel pressure gauge I’m not installing one in the dash. Thanks again


*what really turns me off the most is ordering things online. I’d rather pick things up locally and support my small town’s local businesses. It’s been the longest month of my automotive life just due to availability of parts locally, and having to wait 5 days between orders online. It’s not even running yet. I was honestly just expecting a refresh on this one, not electrical gremlins. Really kills your spirit. What I mean is in a month I’ll easily have a motor and wiring harness from one car installed and running in another. .

Zirconocene

Have you found these yet? http://p914-6info.net/944%20Manuals.html

There is good diagnostic info in there on some of what you're looking at.

I know it's a little bit of a bummer for you, right now, but these are great cars when they're running right and, if you can be patient with the repairs, it will be rewarding to drive.

Good luck

T&T Racing

Go to Clark's Garage for the best maintenance manual and use RL advance search for another source. There are also free Porsche 944 manuals for download on the web.

walfreyydo

You ordered a FPR but did you ever test fuel pressure? I guess you like wasting money

walfreyydo

Sometimes I wonder why I even take the time to post. Did you watch the video on exactly how to test fuel pressure that I posted? Did you read through Clarks as we suggested?

Good luck with your issue.

944#447

It takes many days to get a part in. So while I head to my local fastener stores and plumbing supply to try and locate a schraeder to 944 fuel rail adapter fitting/s so I can maybe use the fuel pressure test tools I already own, I ordered a part that appears to be 41 years old and the possible reason for overfueling.

In the mean time before they opened, I looked through the receipt logs and never found a FPR replaced. So I figure the $80 is worth more then the time I may waste waiting to be able to test fuel pressure anyways. Who knows maybe that’s all it is.

working on this proprietary non SFI fuel system is sure difficult to say the least.

does anyone know the thread pitch and diameter without a doubt on the fuel rail?

I have not had time to watch the video I have however spent the last few hours sourcing and learning about what workshop manual/s to buy so I can be confident in my testing procedures.

I will test fuel pressure as soon as I have the correct tools to do so.

it’s really a shame I can’t run to my local auto parts store for literally anything for this car. Not even the tools to test the fuel pressure.

944#447

For reference, while I wait, I’m trying to use the fuel pressure test tool I already own so I don’t have to buy or build a proprietary tool.

**the ball is safe

944#447

Local hose supply shop said challenge accepted so I’m heading over there

944#447

944#447

35 ish psi while cranking, the perspective here is to the left so it looks closer to 32 in this pic.



So the FPR appears to be working and its been holding steady at 15 psi for a few min after cranking it





Whats the spec/sweep on the temperature sensor? I can pull that and test it.

I guess I'll go rent a noid lighf if i can. If I can't ill order one online

944#447

I rented a noid light and I can't tell if this is normal or not I made a video.


Cylinder 4
https://youtube.com/shorts/NgYA6tfeQ14?feature=share3

Cylinder 3
https://youtube.com/shorts/neWCE3irRQo?feature=share3

Cylinder 2
https://youtube.com/shorts/bg8VD_ziYDE?feature=share3

Cylinder 1
https://youtu.be/smHQ87iYoxU

They all look like they are blinking