Question98 Voyager wont start, turns over fine. No fire, ecu/ecm replaced, crank sensor replaced, getting fuel pressure. Mechanic doing above repairs says that he now thinks there is a short somewhere and needs to trace/eliminate individual wires- wiring paths in effort to locate short. Says engine itself is fine - not blown, timing belt is good. Says has checked coil wire.
Any pointers most likely failure points that you could suggest would be appreciated.
Thank you
AnswerHi Jo,
By "no fire" I assume that you mean no spark. If so, and there is 12V on the dark green/orange wire at the spark coil pack when cranking, then the possibilities are that the coil pack is bad or there is no signal to the driver wires of the two coils in the pack that come from the ecu/ecm. If there is no 12V on the dark green/orange when cranking then the signal wire (gray/black) from the cranksensor should be checked for voltage pulsing when the engine is turned by hand using a ratchet on the crank with the ignition in the "run" position. The signal should appear on pin 32 of the plug to the ecu, I believe.
The driver wires from the ecm/ecu to the coil pack are black/gray and dark blue/green and those leads should also pulse voltage when the crank is turned using a ratchet as when testing the crank sensor. They derive from pins 3 and 11 of the ecu plug, I believe.
If those check out then the spark coil pack should be tested. The primary resistance of the spark coils should by 0.51 to 0.61 ohms while the secondary resistance should be 11,000 to 13,500 ohms between the output sockets and ground.
That is the basic circuit for spark output.
Let me know if there is something else I can help with or if you have spark but no start, in which case we need to look at the fuel and mixture ratio controls.
Roland
