gm with no spark

[SilentUnicorn]

hello all
i am trying to fix a gmc 1/2ton serria pick truck 1990.
has fuel, but no spark. it was parked and the next day didnt start. there is power to the coil and to the ign module, cap and rotor are less than 6 months old. we now have a new coil and ignition module. still no spark. Any ideas ?? anyone??


mark

 

[Paul Johnson]

Age of cap/rotor are of no consequence. Those rotors had a tendency to burn through, so look at both carefully.

 

[philman]

is there an alarm system on the truck?

 

[SilentUnicorn]

putting a rotor on today, and there is no alarm system on the truck. also jumping the obdI gives no code other rhan the diagnostic mode code.


mark

 

[Steve]

Is the HT lead from coil to the distributor cap okay? Try replacing that, or at least ensuring that it's secure if it's fairly recent....I would suggest that's a suspect.

 

[aeronca65t]

Sometimes with cases like this, it's worth cranking the car over after it's nice and dark.
You might see some "spark traces" jumping from the cap, wires, coil or whatever.
I usually "help" this test by misting a bit of water on the engine before cranking.
I don't recall if these cars have a ballast resisitor...the ignition module was my first thought too.

 

[jcatnite]

Sounds like a hard fault. Most sensors would just give an error and the ecu would put it in "limp" mode. Ignition module would have been my first guess but since that is replaced it most likely isn't the culprit. There isn't a crank sensor or a cam sensor on this vehicle is there? There has to be some pickup that is telling the electronic ignition to fire. I'm just guessing though. I wouldn't suspect plug wires so much. If the high tension wire from the coil checks out good it might be time to test other sensors.
JC