IS MY 83-944 DME UNIT FRIED?
05-17-2007, 11:31 PM
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IS MY 83-944 DME UNIT FRIED?
HEY OUT THERE!MY 1983 944 LOST SPARK THE OTHER DAY AND I 'M THINKING I MIGHT HAVE A BAD BRAIN...I MEAN'T THE CAR!I CHECKED ALL THE POWER SUPPLYS AND GROUNDS ,PUT IN A NEW COIL FOR HA-HA'S.I HAVE ALLDATA AND IT SEEMS TO HAVE EVERY THING IT NEEDS TO RUN,OH I NOTICED THAT THE FUEL PUMP DOESN'T RUN FOR A COUPLE OF SECONDS WHEN I TURN THE KEY TO RUN IF THAT MEANS ANYTHING..IS THERE A WAY TO CHECK THE SPEED AND REFERANCE SENSORS WITHOUT AN OCCILLOSCOPE? I'M THINGING OF TRACKING DOWN A USED DME AND SENSORS BUT I WOULD WOULD LIKE MAKE SURE FIRST.THANKS GUYS..... 
05-18-2007, 11:14 AM
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Ignition switch, DME relay, sensors. Hardly ever the coil. Sometimes the HV wire between the coil and the dist cap. Broken timing belt keeps the rotor from rotoring.
05-18-2007, 11:17 AM
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Try not to hi-jack other threads. The fuel pump runs during engine cranking and while the engine is running. It does NOT run with just the key on. You should hear the pump run for a half second or so after you stop cranking the engine. Listen at the rear passenger side wheel.
If the fuel pump runs with just the key on then someone has hacked the wiring. Not a good idea.
If the fuel pump runs with just the key on then someone has hacked the wiring. Not a good idea.
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05-18-2007, 01:55 PM
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Thanks SO CAL! Rotor is turning ,held long screwdriver to coil hv post -nothing-.the dme is not triggering the coil even though it has all the grounds and power to come alive.The thing I was wondering is if the speed sensor or sensors were bad would you still get a quick fuel pump run when turning the key to run? Sorry about that high -jack ,it was late and I was learning how to navigate in this forum,---story of my life.....
05-18-2007, 02:04 PM
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The DME relay powers the injectors and the DME with the key on (not the aux position). The coil should be getting power also with the key on. The DME controls the second set of contacts in the DME relay for the fuel pump. The current sent to the starter solenoid is also sent to the DME. The DME then closes these second contacts during cranking. Once the engine has started and the DME sees the speed sensor the fuel pump contacts are kept closed by the DME. Note that the second set of contacts (fuel pump) can NOT close if the first set of contacts are not closed.
So if the coil and the injectors are getting power with the key on and the fuel pump runs for a half second or so after you stop cranking BUT there is still no spark then look at the reference (front) sensor connections. Loose and/or corroded and/or cracked plastic connectors are the usual suspects.
Remember that everything is simple once you understand it.
So if the coil and the injectors are getting power with the key on and the fuel pump runs for a half second or so after you stop cranking BUT there is still no spark then look at the reference (front) sensor connections. Loose and/or corroded and/or cracked plastic connectors are the usual suspects.
Remember that everything is simple once you understand it.
05-18-2007, 02:30 PM
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Thanks SO CAL!The coil and injectors are powersd up but the fuel pump does not run no matter what .The DMEis not sending the ground signal to the fuel pump relay at pin #9 to complete circuit for pump.The relay clicks with key but the other side of the relay is working do to the no spark condition.I have ALL-DATA -so I'm really learning what makes this sucker tick.Well I gotta get back to work ,thanks man I'll keep you posted...........
05-18-2007, 08:42 PM
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Check the fuse for the pump. Use a jumper from aux fuse 3 to 2 (count from the door it's the fuse holder with out the cover) to run the pump. Does not require the key being on. Check that the pump actually runs. If so replace the DME relay then test is all again.
If AllData was so hot you would have this fixed by now!
Try www.clarks-garage.com
If AllData was so hot you would have this fixed by now!
Try www.clarks-garage.com
05-18-2007, 11:32 PM
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OUCH! ALL-DATA is all I have for diagrams.... anyway--the first thing I did is put a new relay in,then I jumped power to the pump fuse and I heard it kick on in the back of the car.I then checked for spark and realized ,no sparky,no pumpy.I went back to ---yes---ALL-DATA---and printed out the 35 pin ,DME connector diagram and with a volt meter checked every input for power and ground and to my surprize they all came up good.The coil has 12 volts and has a good connection to the DME for trigger.I know it might be rare but it sure looks like the DME the culprit.It would be great if I had a spare but don't ,so if any one out there has one to sell at good price I'm game. thanks guys.....
p.s. My brother says I should pay a crackhead 25 bucks to get one.
I wonder about that guy ....................
p.s. My brother says I should pay a crackhead 25 bucks to get one.
I wonder about that guy ....................
05-19-2007, 02:26 AM
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Having decent electrical diagrams is just half the battle. You need to understand the logic behind the injection/ignition system. If you have voltage to pins #18 and #35 on the early DME's with the key on you should also have power to the injectors. All come off of the first set of contacts in the DME relay. This is non-fused power. If there is power to the coil but no power to the DME and injectors it's the DME relay or related wiring. Note that some alarms do interrupt the power to the DME relay.
The trigger for the DME to ground and release the coil for spark comes from the reference sensor (front). The leads of the large transistor that fires the coil have come unsoldered. There is a recent thread about resoldering them.
The signal from the speed sensor (rear) keeps the pump running once the engine starts.
The fuel pump is Aux fuse #2.
The trigger for the DME to ground and release the coil for spark comes from the reference sensor (front). The leads of the large transistor that fires the coil have come unsoldered. There is a recent thread about resoldering them.
The signal from the speed sensor (rear) keeps the pump running once the engine starts.
The fuel pump is Aux fuse #2.
05-19-2007, 03:50 AM
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Hey joe.
I am trying to track down the same problem on my car.
SoCal seems to be the one who was helping me GREATLY on pelican boards.
I'm very interested in seeing how your problem turns out while I wait for my Noid light to come in.
BTW. what year car do you have, joe?
I am trying to track down the same problem on my car.
SoCal seems to be the one who was helping me GREATLY on pelican boards.
I'm very interested in seeing how your problem turns out while I wait for my Noid light to come in.
BTW. what year car do you have, joe?