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Troubleshooting 944 Turbo DME Relay Issues - Tech Article

Hi everyone,

We've just completed our DME troubleshooting tech article for your reading pleasure! Your input is invaluable and we're ecstatic to read all of the responses - keep it up!

Here's the article:
944 Turbo DME Troubleshooting

Mark at Pelican Parts
Old 02-23-2015, 02:09 PM
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Next Step, Fuel Pressure Testing

Keeping with the fuel investigation (based on your comments), we're looking at fuel pressure as a possible culprit. So our testing order looks to be fuel, then air compression and finally, spark.

We located the cap at the end of the fuel rail and removed it using a 19mm wrench. Keep in mind not to lose the metal ball bearing:





We then attached the pressure gauge to the end of the rail. Next, we jumped the relay using a jumper which incorporated a fuse and switch:





So with the gauge attached, relay jumped (fuel pump operating), we saw almost 2.5 bar of pressure. For reference, the yellow arrow indicates what a 16 valver would see.



Even though we're unable to start the engine, with the relay jumped, the fuel pressure looks pretty good.

Looks like a compression test is in our immediate future!
Old 02-23-2015, 03:18 PM
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NOW we are finally getting some place, why not spark and injector power instead of compression

Last edited by I FROGGY 944; 02-24-2015 at 04:45 AM..
Old 02-24-2015, 04:40 AM
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I second what Froggy said...even if you have low compression on a cylinder or two it should still run (or at least fire). Check spark next and then injector power.
Old 02-24-2015, 09:06 AM
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Quote:
Originally Posted by I FROGGY 944 View Post
NOW we are finally getting some place, why not spark and injector power instead of compression
Maybe this is a way how to demonstrate the full range of troubleshooting
Anyway, this thread returned some life to the 944 turbo forum.
Old 02-24-2015, 10:41 AM
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Four days?
Guess I'll check back in a month to see if it's running yet.
Old 02-24-2015, 04:33 PM
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Next step, no tools required, look in timing belt inspection hole next to distributor to verify timing belt exists.

Next: pull # 1 plug wire, insert a spare plug, ground the plug.
Check for spark.
If you get a spark when expected, this gives a pretty good indication that the DME part of the DME relay works, the crank triggers work, the coil works and the rotor is rotoring.
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Old 02-25-2015, 02:49 PM
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Start with the basics first. Has anyone checked to see if the battery is new, or rather fully charged? You need at least 12.5volts for the fuel injectors to fire. Does the car start and run for a few seconds if starter fluid is sprayed into the input manifold?

Did the car come with maintenance records? Check the records to see when the last full maintenance was done and what specific components were replaced. Such as: reference and speed sensors.

If no records came with the car, then I would do a full tune-up (rotor, distributor cap, spark plug wires) as well as timing components being replaced with new parts (timing belt, balance-shaft belt, rollers, seals for all components and the oil-cooler). I guess what I am saying is conduct an entire 50K mile Porsche factory maintenance. After all, this is Pelican Parts and you have everything you need including many, many great minds (mechanics) available as well as the Pelican Parts World famous "Search" function.

Good luck and I know I look forward to this car running at tip-top performance again!

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Last edited by TibetanT; 03-02-2015 at 02:00 PM..
Old 03-02-2015, 01:58 PM
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This thread is like watching paint dry!!! That with beating a dead horse that's reincarnated every other night. ha ha ha


ps. You're gonna need to do vac lines in the near future.
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Old 03-03-2015, 09:00 AM
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Quote:
Originally Posted by AZ_porschekid View Post
You're gonna need to do vac lines in the near future.
Oh the memories that statement brings back
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Old 03-03-2015, 01:02 PM
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Lit Show and Swap delays but we're back on the 951!

We've been offline for a while preparing for this past weekend's Lit Show and All-Porsche Swap here in Southern California but that's done and now back to the 951 project with out interruption!

Today we took a quick look at fuel flow delivery/fuel volume.

We disconnected the return line from the fuel regulator:





Once the line was disconnected, we utilized a large liquid container to catch the fuel:



Again, we had to jump the relay since our engine does not run. We ran the pump for exactly 30 seconds. Next, we poured the gasoline from the catch container to a measuring container and ended up with 850ml which is a perfect amount for our blue pump vs. a green pump which may yield 750ml over 30sec.





Great suggestions so far and later today we should be done with the compression testing - fingers crossed! Several of you suggested spark, so if all goes well with compression, spark will be next!
Old 03-10-2015, 10:20 AM
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depending on how long the car has been sitting, not running, the fuel may be bad and/or the injectors might be stuck.
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Old 03-10-2015, 11:58 AM
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nynor - we've replaced the fuel with fresh stuff and yes, there could be an injector issue. Almost done checking the compression, doesn't look too bad so far.
Old 03-10-2015, 03:53 PM
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Compression testing results....

Many of you have mentioned compression and we wanted to check out the health of the engine as well.

So we began by evaluating access to the plugs and as you can see, plus many of you are familiar, that the 2,3 & 4 plugs are easily accessible while #1 is partially blocked by the turbo pipe:



We started by removing the three fasteners securing the air box lid, then we disconnected the line running to the turbo pipe with a 17mm wrench. Note that there are two washers (red arrows) that need to be replaced if you remove the line.





We then removed the pipe exposing the plug wire. We gently removed the wire at the boot base, then removed the spark plug. For this test, we used your standard-issue compression tester which you can also rent from most auto parts stores.



A typical tester will have an end that looks like this with the different thread sizes and rubber O-rings:



We threaded the tester end into the spark plug port hand tight, no wrench needed, and zeroed the gauge! And again, we removed the fuel pump relay (getting really good at this!) and turned over the engine for what seemed about 5 or 6 compression cycles or until the gauge reached a max compression reading.



So compression on our 951's engine wasn't all that bad but more importantly, we don't have a bad cylinder:

#1 150
#2 148
#3 150
#4 150

Here's our detailed article for compression testing:
944 Turbo Engine Compression Testing

Most of you suggested spark so that's up for later today! We'll report back shortly!
Old 03-11-2015, 10:15 AM
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A bad cylinder would not cause it not to run!
Old 03-11-2015, 01:32 PM
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Please Restate Your Objectives for this Project


I am game to share my serious experiences and suggestions, but this thread has become kind of "mee too" in the way that serious 944T/951 players are avoiding. Can you directly state what you want to accomplish? Those of us who are both interested and serious will provide more input.
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Old 03-11-2015, 06:40 PM
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Dang You Are Lucky!

Quote:
Originally Posted by Mark at Pelican Parts View Post
Many of you have mentioned compression and we wanted to check out the health of the engine as well.

So we began by evaluating access to the plugs and as you can see, plus many of you are familiar, that the 2,3 & 4 plugs are easily accessible while #1 is partially blocked by the turbo pipe:



We started by removing the three fasteners securing the air box lid, then we disconnected the line running to the turbo pipe with a 17mm wrench. Note that there are two washers (red arrows) that need to be replaced if you remove the line.





We then removed the pipe exposing the plug wire. We gently removed the wire at the boot base, then removed the spark plug. For this test, we used your standard-issue compression tester which you can also rent from most auto parts stores.



A typical tester will have an end that looks like this with the different thread sizes and rubber O-rings:



We threaded the tester end into the spark plug port hand tight, no wrench needed, and zeroed the gauge! And again, we removed the fuel pump relay (getting really good at this!) and turned over the engine for what seemed about 5 or 6 compression cycles or until the gauge reached a max compression reading.



So compression on our 951's engine wasn't all that bad but more importantly, we don't have a bad cylinder:

#1 150
#2 148
#3 150
#4 150

Most of you suggested spark so that's up for later today! We'll report back shortly!
DANG, YOU ARE EXTREMELY FORTUNATE WITH THIS RESULT. Again, what do you really want to accomplish Mark?
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Old 03-11-2015, 06:56 PM
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Checking for spark

We see the light at the end of the tunnel! Checking for spark this morning and no spark to be found. A quick test revealed this so now we'll cut to the chase and test the coil itself.

Old 03-17-2015, 03:46 PM
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i hope the belts have been changed.
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Old 03-17-2015, 06:15 PM
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check the coil with a timing light ,if light comes on check the rotor i had one that was crack on the inside and was shorting to the camshaft, good luck.NOW can i get help with my 911 started the car once a month then had to move it, no start try fuel, ignition,then realized that the air box is blown the car was not even moving. THANKS
Old 03-18-2015, 01:46 AM
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