hi guys,,,,...im done....
the car ....my brothers 72 satellite 318/904
the problem,,,....starts fine when cold ..runs 30/40 mins ..then dead stop...no spark at coil lead on upon cranking....
replaced all new parts.......ignition switch
....distributor
....ecu x 3
....eng bay wiring harness
....ballast resistors numerous (dual )
....coil
....volt reg
....pulled bulkhead connector cleaned , checked continuity everywhere , every wire....
....done everything known to man...!!!
....tested resistive ohms, voltage everywhere , had complete dash out of car back to firewall, every connection and crimp joint cleaned and tested...fusebox, etc etc etc..
now the strangest......after its been running and stops dead ( when warm) it has no spark upon cranking then when you turn it off it lets one spark go from the coil lead....
(thinking ballast resistor )
now if when hot , I unplug distributor ,just plug in another distributor...earth it and spin the shaft I have a beautiful intense spark rom the coil...so to break it down..
when its warm. it loses all spark, then hook aup another distributor , earth it. spin shaft by hand , it has a beautiful full spark!...
stranger....with ignition on, not cranking or running unplug ecu, plug another ecu in , then earth the ecu it throws a inch long spark out of the coil lead!...can any of you mopar igniton tech heads help out a frustrated aussie? I drove this car all over los angeles before I shipped it home never missed a beat...must be the clean aussie air!..
How are your battery cables and ground connections?
This sounds like the typical Mopar ECU "Ground Loop" problem.
Basically the magnetic signal from the Dist is referencing the engine block ground, and the ECU is referencing the chassis ground (if the ECU case is even grounded good?
What happens is when the wiring gets hot, it creates higher resistance. Because voltage is Current * Resistance (V=I*R), the starter cranking current in the ground cable to the battery will have a voltage created. Because the Dist magnetic pickup is using a ground reference at the block, the signal at the ECU is at too high a voltage to sense the pickup signal.
Best fix is two parts, First good battery cables and ground connections, and second a ground strap from the engine block to the ECU box.
