83 944 that won't start

[devilock138]

Hi,
I am brand new to this forum, but have come across some very helpful information from my googling.

I recently purchased an 83 944 that is not getting spark. I have found information from this forum and others as well as clarksgarage that I have been using to troubleshoot.

I have basically narrowed it down to an issue where the DME does not appear to be getting power.

I have:
replaced timing and reference sensors
replaced timing and reference sensor harnesses
replaced DME/Fuel pump relay
replaced the coil

I tested the outputs from the reference sensors through the DME 35 pin plug and they appear to be within the correct range for AC voltage, about 1.5 V on speed sensor and .1 V for the timing reference sensor also both read about 800 ohms resistance. However, I checked pins 18 and 35 on the DME plug and found no voltage. I believe these are the pins that power the DME. I was expecting to see 12V with the ignition on. My guess at the next steps would be to check the ignition switch. I also noticed that there was an additional keyhole on the driver side behind the door, which I believe is for the factory alarm(I don't have the key). Perhaps that should be bypassed.

Was wondering if anyone could offer any other ideas on what could/should be checked?

[John_AZ]

Alarm! yes bypass.

http://www.clarks-garage.com/pdf-manual/elect-23.pdf

Then
Even though you changed the reference sensors and DME/fuel pump relay....

Did you try the DME relay 'jumper?

http://www.clarks-garage.com/pdf-manual/fuel-05.pdf


When you crank the engine with the key in the ignition..............

DO you get tach bounce---a little bump of 1/16th of an inch

When you look at the DME computer---do you see water damage?

Try tapping on the DME computer---wiggle the thick wire connector---carefully,
then start looking for a spare DME on ebay or parts wanted-----usually about $100 for the early 944.

Whether you need it or not, it is good to have a spare.

Here is the basic troubleshooting/no start info on Clarks Garage.
Troubleshooting - Engine

GL & welcome!
J_AZ

[devilock138]

Thanks, John_AZ
I have not done the relay jumper, and I will probably try that next. Wish that the relay was more accessible. Had a heck of a time getting it out.

tach does not bounce when I try to start it, but I did notice just the slightest wiggle when I switch from "ON" to "OFF" on the ignition

DME does not appear to have any water damage. The entire interior is dry and does not have any smell like it was wet before.

I have tried wiggling the dme plug and tapping on it.

I believe pins 18 and 35 on the DME plug should be getting around 12V when ignition is on and that these pins are what supply power to it.

I'll try that alarm bypass too.

[GGX2]

Since the timing and reference sensors were replaced and you said you have no tach bounce, try to switch the sensor connectors. They may have been put on the opposite plugs, this was the case on my 83 when I got it.

Good luck.

[John_AZ]

+1^

Then go back to basics.
The early 944s had electrical/connection/relay/fuse/wiring ghosts

Check the relay panel for connections and burnt wires. Check the fuse panel for loose connections between the fuses and connectors.

Check the POS battery connector. Make sure the small 3 wires are clean and connected.

Check all the grounds.

Make sure all electrical connections on top of the engine are clean ---especially the AFM, car will not start if loose.

Keep looking for an early DME computer or a friend who can test yours. Pro testing is $50 with Specialized ECU Repair. Repair with 5 year warranty I think is $500 +- maybe less.

J_AZ

[devilock138]

Thanks for all the advice!
I have a feeling that the issue is with the dme relay. The whole panel is very loose and I am not certain that I have seated the relay completely. That would make sense since the DME is not getting voltage. I will also bypass the alarm. I think I found the control unit buried behind the stereo. Can barely get my hands on the plugs to pull them from the side. From the front, it is impossible.

If anyone knows someone in the Atlanta area with a running early 944, let me know.

Again, thanks for everyone's replies.

[devilock138]

I now have power to the dme, but I fear that the dme may be the culprit.
I have:
Confirmed 12 v on pins 18 & 35 on the dme plug

Confirmed that I am still getting output voltage from the speed and reference sensors.

I performed the 3 way jumper on the dme relay terminals connecting 30 with 87 & 87b(When I did this, the fuel pump started to run, even with the key off)

Confirmed voltage on terminal 30 at the dme relay

Confirmed voltage on terminal 86 at the dme relay with key "ON"(This should indicate that the alarm is not part of the problem, I think)

At this point, I am thinking to get an ecu swap from ecudoctors.com.

[spec guy]

dme relay is the same for early and late so if you know anyone with a 944 swap the relay to see if you get start

[Panzer909]

I had a similar no start issue two weeks ago. I super-cleaned all the contacts (particulary the starter contacts) and it fired right up. I initually ruled this out because they visually looked okay. Might be worth a shot if you haven't already

[kcoyle]

Maybe its the Mercedes plate on the front? Sorry, couldn't resist.

[devilock138]

the DME Relay I am now using is brand new. Even bypassing the relay, I get the same response. The way I look at it, if the DME is getting power and the crank/speed sensors are sending their signals properly, the DME should fire the coil.

The Merc Stern is vestigial from the previous owner. Not sure why he put it there, but I'm pissed about the plate holder and the self tapping screws he used. It put some nice gouges into the bumper. Probably going to put the front plate holder back and get a different plate, perhaps a nice airbrushed one that says "no fat chicks", "life's a beach" or something like that

[John_AZ]

Pelican has a "Used parts for sale or wanted"
Porsche 924/944/968 Used Parts For Sale & Wanted - Pelican Parts Technical BBS

eBay?

GL
J_AZ

[toyhole]

Hi. The sensor wires can be reversed; if they are not correct the engine will not fire, check/ reverse the connections for the Crank/speed sensors.
Bill in Augusta, GA

[kinein]

Sub

[devilock138]

Tried switching the sensors to each others' plugs, but no dice.

[Gawernator]

Could you swap for a good DME

[mattdavis11]

Sounds to me that the ignition switch could be the problem, but I'm leaning towards connections. The early cars aren't prone to DME failure due to water, the location is under the steering column, not on the floor.

Peel back the heat shrink on the wires going to the positive battery terminal, specifically the small one. Got me once, and it wasn't a problem I was after to begin with.

[devilock138]

I've checked the ignition switch and the wires coming off of the pos battery terminal and everything looks good. I also confirmed that I am getting +12V on pins 18&35 on the DME plug, which are the ones that supply power to the DME.

[mattdavis11]

Open up the DME and check for ring cracks on the solder joints.

[Marks924S]

My 83 had a similar issue, turned out to be a bad connector of the Temp sender on the head, the connector had crumbled an fallen off, put a new one on and never had the problem since. I do have a spare working DME I'd let for little money. Hope you figure it out!