electrical problems

[Marc M.]

Having a problem with my 77 bronco where spark to plugs fails after about ten minutes of engine running? Then after about an hour or two truck will start again and run fine! I changed module, coil, D. cap and rotor and still have problem! Just can't figure it out. Anybody have any ideas? Thanks.

 

[gearida]

Sounds like I would check the gas cap for a vent.

 

[Explorer]

Only thing that pop's to mind is the ballast resistor or coil wire.

 

[Viperwolf1]

The stator inside the distributor could be on it's way out. Measure resistance from the purple wire to the orange wire with distributor unplugged. Should be 400-800 ohms. Resistance from either to ground or the black wire should be more than 70K ohms. Check it hot when you have no spark. You can check the voltage to the coil positive terminal with key ON to determine if the resistor or ign switch is bad.

 

[Marc M.]

Thanks for responding, I was considering the Ign. switch and also replacing the distributor. I'll check that out, and get back to ya.