The truck, 1978 F250, 460, is hitting a wall at about 45-50mph when going up over the local mountain here. It's like a giant flat spot in the throttle where the engine is running but just continues to bog and slow as the grade gets steeper. Used to be she could fly over at 60+ without even really trying. This problem seems to come out of the blue, and only seems to be present when going uphill. Heavy throttle in city or on flat highway yields no hesitation.
Just did a tune-up with new plugs, wires, distributor cap and rotor, ign coil. Didn't solve the problem.
Re-wired questionable wiring for the ignition coil and distributor. Didn't solve the problem.
Checked ignition timing. Base is 10 deg adv, and goes up to approx 36 advance. Seems normal right?
Accelerator pump on carb is working.
Fuel filter is easy to blow through so I'm not thinking it's that...although I haven't checked the microfilter up near the carb. It's not that old though (3 yrs, installed when installed the Demon 625).
Would old"ish" gas cause this prob? The truck is usually used to some extent over the course of a couple weeks, but just prior to it having this problem it had sat for about 4-6 weeks. And the gas in it was probably closer to 2-3 months old. After it hesitated over the mountain I topped off the tank with fresh gas but the majority is still the old stuff. Any recommendations on fuel additives I could try if this is the problem?
Just did a tune-up with new plugs, wires, distributor cap and rotor, ign coil. Didn't solve the problem.
Re-wired questionable wiring for the ignition coil and distributor. Didn't solve the problem.
Checked ignition timing. Base is 10 deg adv, and goes up to approx 36 advance. Seems normal right?
Accelerator pump on carb is working.
Fuel filter is easy to blow through so I'm not thinking it's that...although I haven't checked the microfilter up near the carb. It's not that old though (3 yrs, installed when installed the Demon 625).
Would old"ish" gas cause this prob? The truck is usually used to some extent over the course of a couple weeks, but just prior to it having this problem it had sat for about 4-6 weeks. And the gas in it was probably closer to 2-3 months old. After it hesitated over the mountain I topped off the tank with fresh gas but the majority is still the old stuff. Any recommendations on fuel additives I could try if this is the problem?