Help!
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Senior User
Joined: Jan 2009
Posts: 100
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From: Howell
Help!
ok. so my dad has an 85 f-250 with a 4.9L. rare, i know. but lately its been having a hard time running. it idiles very erradic, if at all. any time you shift down or slow down to stop or turn it dies, and you either have to pop the clutch or crank it. i've rebuilt the carb, and i've replaced all the usual things, (plugs, wires, dist. cap, rotor) but it is still doing it. i've tried three different firing patterns but to no avail. someone please help...
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Check the float height and drop in the carburetor. Unforunately the Carter is not a carburetor that you can run with the air horn removed, so you can't watch the fluel level with the motor idling. You'll have to measure the float height and drop. Also check for vacuum leaks. With the motor idling, spray some carb cleaner around problem areas (carburetor base, intake manifold flange, power brake booster, etc) and listen for a jump in idle, which indicates a vacuum leak at that location. You should also verify your EGR valve is not stuck open, and as a final check, use a timing light to observe your base timing.
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