No start, Weak Spark

1990BlackSC

Registered User
I have a 1990 SC thet has a rebuilt engine. New everything, New autolite platinum spark plugs, New DIS module, New coil pack, new spark plug wires.
We had it running once, shut it off and now it won't start.
It ran smooth when it was running.
Fuel pressure 40 lbs
Have seen situation where cylinders 1,2,3 will not fire, but cylinders 4,5,6 will.
Other times using timing light, various cylinders fire with no rhyme or reason.
 
Auto? Does the upshift light come on when cranking? If so, it's not getting a crank signal.

Verify all the wires are hooked up and proper. Are you aware of how the coil pack works? The coils, wasted spark ignition, two cylinders fire on each discharge, with one spark wasted. If you've seen spark on all wires, that rules out a bad coil pack. The coil pack get's it's go signals from the DIS module. Did you make sure the bottom right screw on the DIS module is connecting well? That one, or both the ones on the right are used to ground the module.
 
I would check for fouled plugs. Also with the new engine is everything stock or do you add upgrades?
 
Weak spark

Everything is stock. It had a blown head gasket when we bought it. Is there anyway to check to see if the DIS module has gone?
 
It would need to go onto a scope to check the dis. If you have another SC owner close buy you could swap the parts with them and see if it helps. Make sure its a DIS and not an EDIS though. (94/95 have EDIS)
 
Mike8675309 said:
Auto? Does the upshift light come on when cranking? If so, it's not getting a crank signal.

Verify all the wires are hooked up and proper. Are you aware of how the coil pack works? The coils, wasted spark ignition, two cylinders fire on each discharge, with one spark wasted. If you've seen spark on all wires, that rules out a bad coil pack. The coil pack get's it's go signals from the DIS module. Did you make sure the bottom right screw on the DIS module is connecting well? That one, or both the ones on the right are used to ground the module.

Not sure if the upshift light comes on when cranking ??? I'll have to check
that.

I'm aware of how the coil pack works. Using the timing light as an indicator,
if #1 fires then #5 should also fire. Sometimes it does, sometime it doesn't.
If I disconect a plug wire at the coil, the spark will jump a good 2 inches. If
I pull a spark plug and its wire, the spark plug barely fires. All the plug wires,
measured with a ohmn meter, appear to be O.K.

The screws on the DIS module you refered to are both grounded. The DIS
module reads 1 ohmn to ground.

Reading some of the other members troubles, there appears to be some
question about the type of spark plug to use. Autolite platinum O.K.???
 
That plug should work just fine. Keep in mind that with the wasted spark design, if that spark plug isn't the one on the combustion stroke then that one will have less energy and also is setup to jump center electrode to outer electrode. Opposite of the one that's supposed to fire the combustion charge.
 
Back
Top