78 C35 HEI/Ignition Woes

[jared p]

Started running funny, cruising on freeway, for a second, would feel like something just put a finger on it and it'd load down a little and then poof, would go away. Did that for a few weeks, wasn't sure what was going on or even where to start looking.

Fast forward, on a drive home it gets worse, then dies. Turn key, crank crank crank, no spark. And cue tow truck.

Get it home, tested parts, hooray this tested bad, replace it! Replaced ignition module, internet says this is what always breaks so, easy peasy and bam, nothing. crap. replaced ignition coil cuz it tested bad. nothing again. ok now...well, replaced pick-up coil.
 
Remembered blinkers act up. flash like normal speed, then suddenly speed up to 1.5x speed or more, then go back. anyway, It wouldn't start... Charged the battery, and it started... Tweaked the timing so it ran smooth, went to hook up the timing light and it died as soon as I touched the #1 wire. Started again perfectly, checked timing and got it in the ballpark, waiting for it to warm up, touched the gas pedal and it died. Now won't start.

next up, new ignition switch is coming tomorrow.

so forum guru's, what say you? after this i'm out of ideas

[Irish_Alley]

stop tossing parts at it.

did you test the coil or someone else and how was it done?

what have you replaced?
ignition coil?
ignition control module?
pick-up coil?
cap and rotor?

[jared p]

stop tossing parts at it.

did you test the coil or someone else and how was it done?

what have you replaced?
ignition coil?
ignition control module?
pick-up coil?
cap and rotor?

yes, tested each part before replacing it. had bad signal off the module. replaced it. bad signal off coil. so, replaced it. after replacing them they both tested properly to spec on multimeter, same story with pickup coil. haven't done cap and rotor. ignition switch was giving lots of different readings, never constant or consistent so, i'm taking that as bad and so, replacing it.  so far, ign coil, pu coil and ig mod replaced, next is ignition switch. other thought could be roll pin on shaft holding gear in place but, tested it, works fine. so...Rotor is spinning, timing is where it started and all that good stuff. It was running at about 8° BTDC when it was running, but can't do the final timing until it's warm and vacuum advance is disconnected. Plus the thing makes sparks. I tested it on the bench with a scary looking fabri-cobbled setup involving a 12v tool battery, plus it fired up when I put it in. It apparently just doesn't seem to work reliably while installed in the truck. Testing the switch it was all over the place in resistance while checking the various functions, it would only go to no resistance on the ignition circuits when I held it just right - and gave it a little jiggle. Given that there is ultimately only one wire going to the distributor, hopefully the gremlin is running out of places to hide

[Irish_Alley]

how did you test the ICM. afaik it can only be tested with the appropriate tester and you have to go to the parts store. and the pickup coil cant be tested. when i worked at autozone we had books on this stuff and these are the pages for the coil from wells

http://forum.73-87chevytrucks.com/smforum/index.php?topic=29995.0

[jared p]

well, new ignition switch. and still bunk. retest things. ah ha. the new ignition module, is bad. put a new new one in. and it hasn't died yet. so, here's to hoping it's good