Engine loses power at 55 MPH
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From: Alvin TX
Engine loses power at 55 MPH
67 F-100 with 240. Engine loses all power cuts out at 55mph in third gear. Problem is not RPM related I can floor it in 1st and 2nd and it goes fine. Just converted the distributor to pertronix so its not the points. Any ideas are appreciated. Thankyou.
-Matt
-Matt
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From: Alvin TX
Dont believe it to be timing related I have a timing light its at 10 BTDC pulls really strong through all gears just cant get it over 55 in 3rd. Problem existed prior to pertronix conversion. I have had the truck for 2 months and it has gotten progresivley worse. It used to be intermitent and I could hold 65 on the highway no problem.
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Sounds a bit like a clogged exhaust. In the lower gears you won't notice it as much because of the torque multiplication, but in high you are putting a lot more fuel into the system. I had a similar problem many years ago. I cut the pipe just in front of the muffler and took it out for a spin. The difference was amazing. I brazed the pipe back together and the problem was back. I put on a complete new exhaust system from the manifold to the tail pipe. Didn't feel like messing with a bunch of rusty bolts and pipe. Good luck.
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How old is the dizzy? Could be a torn vac diaphragm or a problem down inside the dizzy...timing can be right, but not enough mechanical advance. Is the carb clean?...kits are cheap. Your gonna be lucky to get 75-80 mph out of a 240 that is tip-top...depending on rear gears. They are plow horses, not thoroughbreds unless highly modified.
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From: Alvin TX
Thanks for the replies. Gonna rebuild the carb tomorrow and new distributor should be here Tuesday hopefully that will take care of it. Coil is not new and a new better flowing exhaust could be in order anyway. I understand this truck isnt going to be fast but it should be able to go the speed limit.
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From: Alton, MO
I had an old Bronco that if lucky would do 55 with a tailwind downhill. It was just a 170. These old trucks usually have fairly low gears which translates into low top end. My guess is something in the advance of the distributor. Do you know how to read a distributor cap? Look for carbon tracking. How it behaves in 1st or 2nd is irrelevant as it is a different type of load. Most likely your problem is not at full rpm which is why when you totally wind out 1st or 2nd it does fine. The load is lighter in the lower gears. Do you have a tach hooked up to it? If not can you get one temporarily hooked up so you know what rpm it starts at? Can you drive through it?
Lead Driver
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From: **** hole San Jose ca.
hmm -I'd first do a basic compression check before just throwing money at it until you find the magic fix. This is the first things you do and workup through until yor find the cause. Check plugs for condition and or color like dry black fluffy color, possibly bad wires, lose power & carb backfiring due to unleaded gas over heating and burning of valve seats most always noticeable in high gear going up hill or passing another vehicle or just putting your foot down on the gas peddle .
orich
orich
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You say it does not fall off in lower gears?Have you ever tried to hold a sustained rpm in all gears?My first guess would be fuel starvation.Sustained rpm in high gear put more of a demand on fuel delivery If it were mine I would first check for a weak fuel pump they do go bad.At the age it is a cheap and easy replacement.Rust in the tank a pinched line, clogged filter,trash in carb.Just possibilities.
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From: Alvin TX
Did a compression test this morning it has 140 psi on all cylinders. Got the carb kit so Ill see where that gets me. Unfortunately it seems it could be a multitude of things. Plug wires appear to be fairly new plugs are new and are a light brown color which to my knowledge is the way they should look and I replaced the distributor cap and rotor when I did the pertronix. Fuel filters are also new. Thanks for the input.
-Matt
-Matt
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Best way to check fuel pump condition is get it started, put a good rag under the carb/fuel line connection, loosen the connection and pull the line quickly and route it into a quart jar. The engine will run long enough on the gas in the carb for you to gauge fuel flow...it'll fill a quart jar pretty quick, so have someone to start and kill it on your command. Do this with the engine cold and the dist. covered.
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