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Lets see.....80 Model K-Jet
Been a while...but here goes.
Cold start OK.
Hot start OK.
Let sit after warm up......No start.....no pumps operating while cranking.
Can Jumper Pumps and make them run....Yes
Are those the symptoms?
Why don't pumps run when cranking?
It sounds to me like the Ignition Module is not supplying a ground signal to the fuel pump relay.
The Relay must receive this signal to "pull in".
It will only do so if the Ignition Module is receiving a signal from the distributor indicating that the engine is rotating..i.e. running.
This is a safety feature that prevents the fuel pumps from continuing to run if the engine stalls..like in a accident.
This signal travels from the ignition module to the coil negative (white/red wire) and from there back to the fuel relay (white/red wire).
The distributor must be rotating and sending a signal to the ignition module which in turn causes the ignition module to send a (pulsed) ground signal to the coil and fuel relay.
This ground signalcauses the fuel relay to pull in and power the pumps.
At the same time, it causes the coil to fire.
When you have this "no start" condition, I would try the following.
Check for battery voltage between the ground and the blue wire on the ignition module with the ignition switch turned to the ON position.
If there is no voltage, the problem is probably in this circuit back to the ignition switch.
Try jumpering a hot wire (12V) to the connection where this blue wire plugs into the ignition module and see if the engine will start.
If so, you've found the problem.
If not...
If there is voltage to the ignition module, check to see if the coil is firing when you crank the engine.
If so, and the pumps don't run, there may be a problem in the wiring circuit between the ignition coil and the fuel pump relay (white/red wire).
If the coil doesn't fire, the problem is likely in the ignition module.
The reason for the no-start after sitting may have something to do with the "heat sink" affecting the ignition module after turning the engine off.
Just a few ideas.
steve
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