Mopar Action On-line – Tech Questions


Tech Question

Josh Tracy, Kirkland, WA, 1969 Plymouth Sport Satellite 318

I just switched to electronic ignition and it worked wellfor a while (though harder to start from the get go, which confused me sincemy understanding is that the spark is increased) as the starting go more andmore difficult you guessed it, no starting now.

I have my DMM (a FLUKE) ahandfull of ballast resistors (resistances check between 0.9 and 1.4 ohms)two pickup coils whose resistance measure approximately 280 ohms mostly newcap and wires, dist. is good……and being the frugal student I am, I havethree different junkyard ECU’s. I have checked all the wiring from thebattery to the switch to the distributor to the coil, etc. all new wiring,good ground….I have done EVERYTHING I can think of and checked the wiringdiagram against all the ones I have (they are all the same except for thetwo or four pronged ballast resistor) and the wiring is good (since it didrun for a time), I get battery voltage in the accessory position and when Igo to the “run” position, boom, it drop to 10.8 or so. Cranking obviouslydoes about the same and as the ballast resistor heats up it drops a bitmore. Is my ECU bad? I’ve tried em all with no change in voltage readings.How can I check one of these things? I put the points distributor back andre-wired the two prong resistor and she fired right up as if to say, “whatare you waiting for?” So, wish I could pin down my loss in voltage and whythe electronic ignition won’t work but the dinosaur system will…..don’tlet my wife be right!

Thanks for any help, Josh


You somehow wired it wrong. I’m sure of that even from 3000 miles away! Howdo I know? The tipoff is that you say the ballast resistor heats up duringcranking. If wired correctly, the ballast resistor is completely out of thecircuit – bypassed- by the ignition switch during cranking. There are a fewways to prove this. The technician’s way would be to take one probe of yourtrusty Fluke and clip it to the battery positive terminal, and the other tocoil positive. During cranking, the voltage displayed should be under onevolt. The pessimist’s way would be to pull the ballast resistor connector(assuming a 4-pin ECU is installed) – the car should still start (but willquit the second the key is released.) The car thief’s way is to run a smallclip lead (jumper) from coil positive to battery pos. The car should startquickly, even by just jumping the starter relay – no key required! (Don’trun it too long this way, the ECU and coil will cook.)

As far as the total death, you need to follow basic troubleshootingprocedures. If you made one wiring error, you might have made more, fryingthe ECU.

These systems are stone-axe reliable. You just screwed it up!



Picture From Tech Archive

Main Index | Current Issue | Tech Q & A | Tech Archive | Subscription | Advertisers Links | Contact Info