I have a spark problem in my ignition system I cant figure out. The vehicle is my 75 Dodge D100. The engine will start up and run then lose spark and die. I know its losing spark because when it turns over and wont start I can hold the coil wire against the frame and no spark. But what I did notice is when holding the coil wire it would spark when the person turning the key backwards (after cranking) and passing thru the "on" position in the ignition switch it would spark. When this happens the engine shakes from trying to fire off the little bit of spark it gets when coil wire is conected. Most of the components of the ignition system are new (not including switch) and it runs great when it has spark. Ive swapped out ecu and ballast resister so far to known good parts with no difference.

It could be the pickup coil in the dist. But before changing it, check the gap between the reluctor and the pickup. Should be about .008

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

My 75 duster had a similar problem, it would not start and no spark while
cranking. But when key is being moved from start to off it sounded like
it almost fired up.
Found high voltage coil wire terminal blue green corrosion, and
inside coil tower socket was brown dust and terminal contact was
brown. I changed coil wire and coil and reseated ecu connector and
now it starts and runs. The coil and coil wire was only 2 years old.
Also the coil resistance checks out okay.

2 years previous , sometimes the engine would run slower and
die out. I changed that coil and coil wire to solve that problem.

I checked distributor pickup clearance and it is adjusted right on .008". I dont see any corrosion on the coil wires but I am going to try changing them out with spares to see what happens. The coil and wires are only about a year old. I'm suspicious of the ignition switch being faulty because I beleive it to be original and am wondering if the problem could be in there? I'll try the coil first tomorrow. Thanks for the replies! Sam

Then test the ignition switch; connect a voltmeter to the coil + & engine ground, unplug the ballast resistor then crank the starter. If the switch & the wiring is ok then you'll have battery voltage at the coil while cranking.

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63 Valiant Wagon
225 - 4 bbl