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Subaru ej20 '99 no spark on front cilinders

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I got an engine wich came in for "not starting after a broken timing belt due to a frontal crash".

The engine was rebuild but doesn't start now. so i visually inspected the wiring and found that the camshaft sensor plug and the injector plug were switched. i sorted that and put the engine on the engine dyno, tried to fire it up but theres no spark on cilinder 1 and 2(these share 1 part of the coil). cil 3 and 4 do spark without a problem.

what i've done:

Put the scope on the coil trigger wire of the rear cilinders. there a good signal on there.

did the same on the front. No signal at all.

I've measured both trigger wire circuits and they are ok , and there's no continuity to ground.

I've pinned out both trigger wires in the ecu plug , swapped them around and plugged back in , then the fronts spark and the rears dont.

I've checked feeds and grounds on the ecu. with ignition on and while cranking. all stay fine.

These factors forced me to conclude the ecu output was dead. so theowner tested the ecu in another car and that just ran fine.

So i am clearly missing something here.

ECU is a prodrive one and i have no acces to parameters.

maybe the cam pully is swapped after the damage with one from a wrong model ?

any input would we appreciated :)


Kenny J

Have you scoped the two trigger inputs to the ECU? It's possible that the ECU may not be syncing correctly. This would typically result in no spark at all but it's possible that the ECU you're running may be doing something unusual.

the trigger signals look fine on the scope yes , its a weird situation.

next up i'll have a look at this ecu in a running car and compare trigger signals to those of the other non running engine.

so last update,

i tested the ecu myself in another car and that was running on only back 2 cilinders also , so ecu was faulty after all

That would explain things!

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