Took my '67 F100 240 engine, 3 speed out for it's shake down cruise on Monday. Not good. Truck has only 12K miles on it and has been stored since 1989. Gas tank professionally cleaned, new fuel pump, fresh gas. I started up a long hill outside town and it began bucking. Runs for 5 seconds, turns off for 5 seconds. Limped home and cleaned the carb but found nothing. Read old posts here and decided on condenser. New condenser, new points set at .025, new plugs. Same results. Check timing and it's at 0 so I bumped it up to 6 deg and noticed it was not advancing. GREAT, found the problem. Today put new vacuum advance in and the truck seemed to run stronger when I drove it all around town. Decided to run the errand that goes up the long hill and bingo, starts bucking half way up the hill again. Turned around and headed home it ran fine. I pulled a steeper but not so long hill earlier today and it pulled it in high gear with no problem. What am I missing?

 

 

Sounds like you covered all the electrical side. What gear were you in? 3rd? Were you lugging it, or was it pulling it strongly right up til it starts to quit? As you increased the load(increase throttle), it starts bucking?
How's the coil? Under the hardest load(3rd gear, low rpm, steep hill), if it is weak you won't get a strong spark and it will not run well. Have you tried the same grade in 2nd gear, slower maybe, but less load on the ignition and see if it runs okay.

We had an 01 F150 and it ran awesome, til you got it on a hill and put a load against it in OD it would start to miss/buck. One of the coil packs were bad.

 

Is the new condenser a ford part or a Chinese one. Put a ford one in and try it again.

 

Update: Heat riser works, condenser from NAPA not sure where it's made. Running 55 mph up the hill mid throttle somewhere. BUT! Checking the timing again I had the air cleaner off and saw a lot of gas leaking out of the throttle shaft on both ends. Shaft has very little play. Went to remove carb again and taking fuel line off it is under pressure and sprays gas everywhere for a few seconds. Checked the float and it seems in fine shape and is adjusted to specs. This problem is kicking my butt but thanks for all the help guys.

 

I'd throw a fresh fuel filter in the fuel pump. They are cheap and easy to replace.

 

I have a '69 Ranchero with a 289 2bbl. It runs well until the fuel starts boiling in the carburetor bowl. It also seems to leak or seep out of the choke side throttle shaft. The most pronounced symptom is a bog from a stop, like no accelerator pump shot. I don't believe I've taken it up a grade as you've described when its boiling fuel, but I expect it might do the exact same thing. 2100 carburetor you can pivot the air horn off while the engine is running and can see the fuel boiling. Good luck!

 

Mike, Autolite carbs are notorious for accel pumps not working smoothly. The pump is actuated by spring pressure off the throttle arm. If the spring is weak and the linkage is stiff, it won't push the pump, thus giving you a bog. I hate Autolite for that design. Heat soak is typically only when you shut it off or sit in traffic for extended time.

Chief, sounds like it's getting plenty of fuel. If you shut the truck off and remove the fuel line and it sprays....then the pump is apparently putting out enough fuel that the needle/seat is holding it back correctly. If it was boiling out, then the float would allow more fuel in and there would be little/no pressure on the line.

That leads me back to the coil? Has it been replaced? If it is weak, under a load you will not get enough spark. That is why I questioned your throttle input. If you continue to ease off the throttle, does it continue to run okay? Only stumbling if you continue to add throttle.

 

Ok. Today I went out (Good thing I'm retired) and put the carburetor back together. Put it on and test drove, found out the hill wasn't the problem. The truck drives about 3 miles and starts to die and I limp home no matter the terrain. Throttle position does not seem to effect anything. Tried a different coil, same results, wired the heat riser open and then closed, same results. Checked the fuel filter, looks new. Seems like the carb isn't leaking but the truck will not go past 3 miles. I will not give up but I have no idea where to go from here.

 

How's the ignition switch? If you have some intermittent contact that can cause the ignition to drop out. Check the wiring and connectors on the back of the switch. If they are loose, replace the socket. Other than that I would be tracing the wiring in the engine bay on back. Might be something shifts, and shorts and that's the issue. My old Toyota had a wire come out of one of the tag lights in the bumper. My dash lights were out so I replaced the fuse. They were on for about a week, then out again. I replaced the fuse, backed out of the driveway and when I stopped the dash lights went out again. The wire was swinging up and touching the bumper. Your hill situation makes me think you have a bare spot or a loosey just waiting to find some frame.

 

I see you replaced spark plugs in your first post. How do they look now?

I think Raputin53 has offered a really good suggestion. Perhaps your problem is heat/resistance related, and am I'm sure you're aware resistance=heat. You could likely rig up an ignition system with your own jumper wires and take that for a drive on your test circuit.

Good luck!

 

Is your muffler plugged part way? Rusted baffles inside or critter nests?

 

Besides a partially plugged muffler, your symptoms could be caused by if your gas cap should be vented but isn't. I had that one time with my COE. Old gas cap fell off never to be found. So I bought a locking gas cap from Bob Drake to replace it, so that I wouldn't have to worry about it working loose and falling off again.

However, by default it is sealed. It is necessary to remove a screw to turn it into a vented cap.

The truck drove great for a few miles until the vacuum in the tank was great enough to stall the engine. There must have been a slow air leak because after 10 minutes or so, it would start right up and run OK for another few miles.

 

Mike, Went out tonight to check a plug. Tip and white part are clean but the inside of the plug is black. I did notice while I was pulling the plug that the fuel line from the fuel pump to the carb runs less than 1/4 inch from the head just above the side cover. Maybe it's getting hot there and vapor locking? Think I'll bend the line or put something like my asbestos gloves between there and take a test ride. My next trick I guess will be to run a wire from the battery to the coil and see if that works. Getting desperate here. Lucky this isn't my daily driver! Again thanks everybody for the time and effort spent on my problem(s). Chief

 

Probably not related to your problem yet something to check. Unless I am badly mistaken you should also have a centrifugal advance system in the distributor. After many years of sitting it may not be free to move and would be worth checking since you said you were not getting any advance. Ball park figure would be 25 degrees of centrifugal advance at around 4000 rpm. Total advance, base+centrifugal+vacuum usually will be around 42-44 degrees.