a 928 owner in the
Netherlands had this problem:
1987 928s4, No start
- no injectors clicking
- LH ok, swapped and worked without problems (even swapped together with EZK
onto another car)
- EZK swapped and worked fine
- Ignition worked, sparks show at plugs from both sides
- temp2 is about 3k ohms at both sensor sides at 20C
- fuel pump is not activated, but runs when you bypass the relay, still no
start
- relays LH, EZK and Pump swapped, no difference
- spray fuel in the MAF and the engine briefly starts
- no alarm start immobilizer existing
- all electrics seem original
So......
Turned out to be the kickdown relay. It caused a load on the speed signal
between EZK and LH, causing the LH not to see a speed signal and thus not
activating normal operation but stay in standby until the engine starts to turn.
No injector pulse yet so no fuel, so no start.
Pulling the #15 relay immediately made the car start.
ps: Funny that the EZK fires the plugs... making you think things are ok with
index pulse and such.
regards
Theo
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And once more I had this problem with another customer (928 owner). He has a manual 928GTS and while troubleshooting at a Porsche Center (workshop for another repair) the car failed to start. Lots of things tried, still no go. Turned out a 53 relay was installed in the kickdown position effectively blocking the engine rpm signal.
regards Theo
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Similarly Rich Andrade had the same issue once. Here is a short write-down of the issue