78 bronco engine shutting off

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Furumo

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Hi all,

I have a 78 bronco with a 400 engine that has been running fine until recently. It starts right up but after about 5-10 minutes the engine shuts off and won't restart until hours later (it will crank but won't turn over). Usually have to let it sit 4-5 hours and then it starts right up again and does the same thing. It runs great for that 5-10 minutes but without warning it dies, rendering it un-drivable.

Suggestions on where to start troubleshooting? My initial thought is that it's running too rich?

 

Bully Bob

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Rich would give you dark smoke out the exhaust.., and a nasty smell.

Usually this is a symptom of a bad coil or elect. ignition module.

While cranking the eng. when it won't start..., check for spark at a spark plug.

 

Seabronc

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That is also a classic symptom of a Duraspark II pickup coil inside the distributor.  They will run until the engine warms up and then the pickup shorts out and it is like the key was turned off.

Read through the troubleshooting procedure, it can isolate between components.

:)>-

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