truck cranks, no spark

[Randysbodyshop]

my 1978 gmc 350 will crank over, but has no spark to #1 plug wire. What would be some things to check for?

 

[Honky Kong jr]

my 1978 gmc 350 will crank over, but has no spark to #1 plug wire. What would be some things to check for?

Make sure your 12v power source to the distributor it functioning. Also make sure your rotor hasn't broke. Also make sure your rotor button on the cap hasn't disintegrated. Also welcome to the site.

 

[1987 GMC Jimmy]

If none of those, I'd take the ignition control module out of the distributor and have it tested at Autozone or whoever does it closest to you.

 

[Honky Kong jr]

If none of those, I'd take the ignition control module out of the distributor and have it tested at Autozone or whoever does it closest to you.

Oh yeah how could of forgotten that it isn't like they fail if you look at them wrong or anything. Big duh on my part.lol

 

[towman]

check the rotor real close those years had a habit of burning a real small hole thru them and made the spark go away

 

[84 C20]

Is the plug not sparking or is there no electricity getting to the plugs?

- seems basic, but check the advance, then check to make sure wires are going to the right cylinders

- check the red wire feeding the module, sometimes it'll come out of the plastic connector and not make good contact thereby not charging the HEI module

- are the plugs fouled?

- are the poles on the dist corroded?

- are the plug wires on tight?

- is the connection inside the cap for the rotor corroded or screwed up?

like the others said, check the HEI module too.

 

[Randysbodyshop]

Ok, thanks everyone. All good suggestions. seems like it should only be a couple of things it could be. So far I have checked the wiring off of the starter. I have continuity thru a fusible link in the wire at the starter solenoid. I have used a test light to confirm power up to the distributor. the cap is newish, so are the rotor and plug wires. upon inspecting the cap and rotor I could not see any problems with them. they all look new.

No corrosion on any connection that I could detect. Plug wires all on tight. Spark plugs are new, and clean.

I checked for spark by taking out #1 plug and grounding it to the engine bracket with the plug wire attached to the plug, and then cranking engine over. It seems to me the only thing left to check is the ignition module and coil.

This truck has been in my garage warm and dry for a long time, and has always started and ran. Then when I recently needed to move it, it would not start.

 

[MrMarty51]

Hold the coil wire away from the top of the distributor cap just a little ways, have someone crank over the engine and see if there is any spark there.
Much better than trying through a plug wire that only sparks on every other rotation of the cranking shaft.