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Tech Question
David Buchanan, Hillsobor, OR, 1968 Dodge A108 318
Thanks for all the help you provide to your readers. You are an awesome resource. I have a problem with my 1968 Dodge van. It has a 318, Auto with electronic ignition. I rebuilt the engine and transmission a couple of years ago and it's run fine with no problems. A couple of weeks ago I drove it to the store and when I returned from shopping about a half hour later, it would not start. I've never had this kind of problem. I didn't have that many tools and did a rudimentary check for spark by holding the coil wire away from ground to check spark. Nothing. Popped the cap and the rotor is turning. I got a ride back to my shop and pulled an old module, ballast resistor, coil and coil wire and drove back over to my van. Each of the parts had worked in the past and were replaced when I would upgrade my other Mopars (MSD, MOPAR performance.) I usually don't try and just throw parts at a project, but it was cold, rainy and I didn't want to leave the rig overnight. I replaced the coil plug wire, no go. Switched out the coil, no go. Swapped out the module still no go. Odd thing was that when I crank it, there is nothing, but when I release the key from the start to run position before going to off, it almost sounds like it's going to start. Just a split second. I know there is always the dreaded bulk head disconnect, but this doesn't have one that I'm aware of. The fuse block is a little rusty but my volt meter doesn't indicate an open circuit. Any recommendations? I did get the van towed back to my shop but I'm kind of baffled.
Thanks again for your great tech and restoration articles. - David
Dave-
I will assume you have converted to stock-style '72-up Mopar electronic ignition, and that you have a 4-pin ECU.
I don't have an A-100 FSM handy as I write this, but, obviously, the wires need to go through the firewall somehow, so I'd look there first -- once you find and inspect the connector, and problem is usually obvious.
Then you'll need to do some real, actual troubleshooting, although it sounds like you wanna keep just throwing parts at it, so I'll mention that you haven't swapped the ignition switch and the pickup coil. The easy way to try the pickup coil is to simply hang another distributor nearby, plug in its connector, turn on the ignition, and twirl the second dist's shaft while checking for spark as you describe.
The first step in troubleshooting is to use a DMM and measure the voltage on the coil's positive lug. With the key in the run position, it should be in the vicinity of 8 to 9 volts, and, during cranking, a bit higher. If it fails the first test, suspect the ballast and / or the "ign run" wiring / switch, if NG during cranking, the "ign start" wiring / switch.
It is also conceivable, but unusual, that your (original) coil is shorted, toasting both ECUs, assuming that you tried the ECU first.
Also, be aware that the ECU needs a good ground to function.
There's a whole procedure to troubleshoot this "by the book", but usually the above will get you going.
Rick
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