6.8 won't start when hot
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6.8 won't start when hot
I have a 1999 6.8 manual trans that gives a problem only in the summer months. After driving and using the AC when the truck is shut off it sometimes will not restart until it sits for minutes, or hours. Starter will operate, but it will not fire, Truck can be push started and it will start up and run fine. I just cannot figure this one out, it does not make sense to me. Anyone have any idea?
Fleet Mechanic
Joined: Oct 2017
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From: Southwest Ohio
When this hot condition no-start occurs, do the following:
- Hold throttle wide open
- Crank over the engine while continuing to hold throttle wide open
If the truck starts while doing the above, you have an excessively rich running condition, possibly caused by a leaking fuel injector.
— Dave
- Hold throttle wide open
- Crank over the engine while continuing to hold throttle wide open
If the truck starts while doing the above, you have an excessively rich running condition, possibly caused by a leaking fuel injector.
— Dave
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I'll try that next time, but it still does not seem to explain why it will start with the smallest of push starts. if it was a "flooded" condition, it should not start by cranking, or pushing, but all it takes is the smallest, short incline, and less than walking speed to fire it up, just enough to roll the engine and away we go. And why only when hot after using the AC? Almost acts like some permissive is not being satisfied when using the starter. Replaced the relay that controls the fuel pump and computer, still the same problem. Was thinking of replacing the crankshaft position sensor, but again, it starts when pushed, if the sensor was bad it would not allow the truck to start either way. As I said, this doesn't make sense.
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Update. Replacing the IAC solved this hot start problem. The truck was also surging when shifted into 3rd gear, and that problem is also gone. Replaced the IAC with OEM Motorcraft parts bought on Amazon(best price).
IAC - CX 1870 or YC2Z-9F715-CA
Gasket - CG-763 or F7UZ-9F670-AB
Thanks Krewat!!!!
IAC - CX 1870 or YC2Z-9F715-CA
Gasket - CG-763 or F7UZ-9F670-AB
Thanks Krewat!!!!
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