Won't accelerate when temp reached...
Thread Starter
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Freshman User
Joined: Oct 2003
Posts: 47
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Won't accelerate when temp reached...
I have a 78 F250 with a 400. The engine starts and runs fine until it reaches operating temp, then it won't accelerate at all. But it will idle all day!
Hooked up an electric fuel pump and nothing changed. Changed the pick-up coil and ignition module and no change. Thought about ordering the KD-tools ignition tester but not sure if will do more than idle? Any thoughts?
Thanks in advance for any help.......
Hooked up an electric fuel pump and nothing changed. Changed the pick-up coil and ignition module and no change. Thought about ordering the KD-tools ignition tester but not sure if will do more than idle? Any thoughts?
Thanks in advance for any help.......
Thread Starter
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Freshman User
Joined: Oct 2003
Posts: 47
Likes: 0
Thanks for the input!
It will accelerate and run perfectly when cold, as soon as the temp needle gets to the 'O' on normal, the motor will fall on its face during acceleration, whether stopped or under a load. If I shut it off and let it cool a little a bit it will run fine until the same temp again.
I have since changed the ignition coil, fuel filter, bypassed the tank selector, made sure the hard fuel line from the pump to carb is not touching any hot spots. Not sure if the m. advance is working. How do you check that, timing gun w/ v. advance unhooked?
Any help is greatly appreciated.....
It will accelerate and run perfectly when cold, as soon as the temp needle gets to the 'O' on normal, the motor will fall on its face during acceleration, whether stopped or under a load. If I shut it off and let it cool a little a bit it will run fine until the same temp again.
I have since changed the ignition coil, fuel filter, bypassed the tank selector, made sure the hard fuel line from the pump to carb is not touching any hot spots. Not sure if the m. advance is working. How do you check that, timing gun w/ v. advance unhooked?
Any help is greatly appreciated.....
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
Check both the vacuum advance and mechanical advance with a timing light. There are directions in a service manual along with some numbers you should see. It sounds like the vacuum advance may go to zero when the Thermal Vacuum Switch by the thermostat activates.
