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Join Date: Mar 2011
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Question Damned Electronics-no spark, no fuel pump

Never had to deal with this on my '66 912, I hate electric, what ever happen to compression fuel and spark???

Ok, 1987 924S, new head (PO made prezels with the valves), full tune-cap, rotor, wires, plugs, compression 145 even of all four (cold 'cause the dog won't bark!!!). Took 5 hours to do a rebuild on the head, light milling, guides, valves, springs and caps and slap it on, got great compression but no spark. 5 days with the meter chasing wires and am skunked.

I can not get spark on the coil and the fuel pump will only go with a jumper on DME relay, so I'm guessing the FP is ok if I could get consistent current to it.

Checked all connections and following sensors/relays, speed, position, injectors, firing (or rather clicking) coil's good (resistance OK) and checked with spare, DME relays good, tried two spare new one (just in case) but no FP hummm, no zap. ECU apparently was clean and has never been down judging by the cleanliness of the box and connections. Did secondary test of my ECU plug - good speed, position, grounds show continuity (except 10 which my ECU guy said was N/A for 924S) Fuel pump worked on jumper, showed 12 VDC at ECU plug. I don't have a scope to check the ECU, don't have a spare (but will be mometarily trolling craigslist for one) ECU to test against. As noted the ECU was clean, no exterior damage or water staining and have not yet opened as I dread the ECU gods.

Mow I could admitt defeat and box the ECU up and send it to the Treatment Spa, but then the sense of annoyment would be way too high if it came back ok or was repaired but I still could not get some spark.

I'm guessing that that little brown line at the fuel pump may not have a clean earth but where would it be? The diagram shows a short run to ground but in chasing it, it seems to join up with the shift sensor and disappear under the back seat. Does it ground there or just run back to that damned ECU???

There are reasons I stick with old cars and I believe this is it-my daughter wanted this black beast so I gotta find the light at the end of the tunnnel!Thoughts, comments or valuim would be greatly appericiated.
Old 03-25-2011, 01:19 PM
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Garage
Did you ck for 12v at the DME could be a bad fuse i just went through this with my 83 944 ck for
connections at the battery the two red wires that hook to the pos. cable that is your supply power
to the inside of the car
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Old 03-25-2011, 03:08 PM
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check both the DME Relay (had 2 good spares) and DMECU, had 12VDC strong. The fuel pump worked when jumped but still had no spark. Pulled the ignition switch this morning (which was cracked at the key end) and put in a new one from the local store. It was odd that they had it but apparently is not a true match-missing pole "P" and marked VW but the computer matches it. Wiring schematic shows a grey or blue line out a pole "P" but don't see where it goes, (see page 3 and can't find it!!!) guess tonight I'm studying all 8 pages of Haynes to see if it's needed. Doesn't the Throttle valve have a blue line in it and would that prevent spark at the coil?
All plugs and connection were cleaned and hit with di-electric grease during assmebly of the head-speed and postion sensor are sending clean signal and I have a jump on the tach during my futile efforts to start it. Gotta be something simple...had wife lock away the shotgun

Last edited by Larry Bud; 03-26-2011 at 12:46 PM.. Reason: spelling
Old 03-26-2011, 12:41 PM
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Old 03-26-2011, 12:41 PM
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