Quote:
Originally Posted by shiftdrift944
ok ill see thanks outback porsche for clearing things up , well the DME it self should be fine since it stared up fine when i got the car, and then i replace the fuel pump and relay and i had to start it with starting fluid everytime...
well i could lose signal from the sensor since; last time i tried to start it, it will start once i had the key back on the on position and then it dies 5 sec. later. i could also check the wiring from the connector of the sensor to the DME plug, and ill see if the resistance are correct.
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You might be right about the sensor signal, since Outback explained the fuel pump section of the DME relay will only stay energized when going from START to RUN if the DME is getting a signal from the speed sensor and the wiring and connections between the DME and the relay are good. 5 seconds is about how long it would run with a correctly operating fuel pump suddenly stopped, seemingly caused by the DME relay losing the energizing voltage supplied when the key is in START when the key is released and not replaced by the voltage delivered when the DME gets the speed signal.
It's definitely a good idea to test the applicable DME wiring. Test the sensor resistance at the sensor connector, then at the DME connector. They should be pretty close, otherwise you have some sort of wiring or connector problem. Test voltage at the assorted inputs and outputs at the DME and relay to see if voltage is getting to/coming from where it sould be when it should. Work from the battery outward to the ignition switch, DME/relay voltage inputs, DME/relay voltage outputs, fuel pump. Somewhere it's not getting through when it's supposed to.
Just like the DME relay which also has solder joints prone to cracking, the DME could just as easily work fine one day and not the next, so it is a possibility if everything else checks out and the voltage is stopping there for no other apparent reason. Others have successfully fixed theirs by re-heating all the solder joints inside.
(just in case you don't have these.)
DME Connector 35-pin
Pelican Parts: Porsche 924/944 Electrical Diagrams