Discussion in 'Engine Performance + Maintenance' started by Mingwro, Jul 28, 2020.
New to forum...is there an existing thread to troubleshoot no spark to plugs...thanks in advance
Check for spark at the ignition coil. If no spark there check the ignition control module and pickup coil on distributer. I'm not too familiar with the TBIs, but I helped my brother's C1500 with the same problem.
I narrowed it down to those 2 items. I think I checked with digital voltmeter in AC mode. The pickup coil is part of the distributor. Luckily for him a new distributor came with both of those 2 things already included.
Truck started right up. Just took him longer to set the timing. Had to buy timing light.
I hope this helps.
thanks...I downloaded wiring diagram....no spark at coil....pick up coil good...changed ignition control module and fired right up
It's funny how many times it boils down to the ICM on these trucks, glad you found it without throwing too many parts at it. I hope you got a good quality ICM like AC Delco, Delphi, etc.
An ICM can fail on it's own. Yup, it's possible.
Fairly likely that the ICM was killed by a faulty ignition coil. The insulation on the ignition coil breaks down over time. The coil develops an internal short-circuit. The short circuit lowers resistance, increasing current (amperage) draw, and at some point, the module can't handle the amperage load so it fails.
This may--or may not--be picked up by ohmmeter testing of the ignition coil. If it tests bad...it is bad. If it tests good...it may still be bad.
You'd want to use an HEI-calibrated spark tester to verify the old coil can still deliver proper spark power.
If it passes the ohmmeter tests, AND it can fire an HEI-calibrated spark tester, the coil is probably good.
Another trick is, while the engine is running, spray some water on the coil body (not the wires on top). If the engine stumbles, replace it. I had a Pertronix Flame Thrower fail at about the same time as my ICM - go figure huh? Don't know which came first but as @Schurkey said, probably the coil 1st.
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