Stumped
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Freshman User
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Stumped
I need someone's advice or ideas. Have a 78 f250 pu, 400 ci 2bbl carb. Problem is it losses power after warm up. I can be going down the road 60-70 mph and she will start to lose power and began jerking like she is running out of gas. I can let up on the gas jpedal and she will quit and if then push baack down starts to jerk. This will go on for about 1/4 to 1/2 mile then quit and run fine. I retimed it, new plug wires, cap and rotor look fine. The only thing I did different is put fuel in the aux. tank that wasn't being used. Is it possible that there is rust in the bowl. And if so why does this happen at approx the same time when I drive it. Thank for your advice.
Elder User
Joined: Jun 1999
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From: SE PA
Stumped
It sounds like the engine is runnin' lean, after the choke comes off. If you had alot of crap in that aux. tank, it may have clogged the filter. This would be most noticable at higher speeds when the engine is lookin' for more fuel. May also have had some water in that tank, although this would effect overall and not just when warm or higher rpm's. Rust in the tank may also be blocking the pick-up in the tank and could cause the same condition. When shut off, the crap drops from the pick-up until you drive a few miles and it gets sucked back up again. Just a thought, Chuck P.
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From: SE PA
Stumped
Just thought of this after re-readin' your post, the choke may be comin' off to soon. If it happens at the same point in the drive after start-up, the choke comin' off to soon may now be makin' itself known with the cooler weather. If you have the warm air(stovepipe on manifold) hooked-up, it may not be pullin' the warm air into the intake and would tend to cause this type of problem until completely warmed-up. There is a flapper valve in the snorkel to the intake, at start-up, this should be in the closed(intake tract pulling from around exhaust manifold)position, if this is not working, the sensor is located in the air cleaner on the bottom with a couple of vacuum hoses. My ranger would do this exact same thing and thats what it turned out to be. Hope this helps, Chuck P.
Posting Guru
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Stumped
very good posts Chuck P. !!! I want to add the probability of the fuel pump being weak,if the other stuff doesn't correct it.Also, a lean out at high speeds could be from a bad gasket under the EGR Spacer Plate, which directly below the carb, before the intake. In my experiences, this gasket is often overlooked if not completely forgotten,and,spraying carb cleaner around it won't show a vacuum leak from the EGR port to the throttle bores,you got to change it to find out.
Phillip
Phillip
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Stumped
Thanks guys for your ideas. I found my fuel pump leaking, replaced it, no help. I am going to change fuel filter and put in a inline fuel filter. In my snorkel the damper is open all the time, no vac hoses. I am running the main tank now , still same problem. I am going to unhook the choke and see what happens. I believe in manual chokes over auto. I run one in my bronco, never have had a problem w/ it. Thanks again, you gave me some more starting places w/ this.
P.S. As far as I can tell all the proper vac hoses are plugged.
P.S. As far as I can tell all the proper vac hoses are plugged.
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My 77 with 351M did the same thing. When the filter becomes partially clogged the truck will run fine at idle and even accelerate ok for a short while until the fuel flow can't keep up with the demand. I replaced the fuel filter into the carb several times and the problem kept recurring. Basically the screw in fuel filters are crap. Take your old one and run a drill bit through it and use it as a fitting to attach the fuel hose to the carburettor. Get a large fuel filter and put it inline between the pump and the carb. The larger filter will not become clogged as quickly. By the way always carry a spare filter when having this problem.
Senior User
Joined: Jul 1999
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Stumped
Something to think about... On my truck, I have gotten an older model fuel pump to fit the engine that has the screw-on cannister on the bottom. These have replacable large capacity elements and the cannister also is a sediment bowl. These are about the same price as a regular replacement fuel pump. Engines such as the FE series, 302, and perhaps the others can be fitted with the older style fuel pumps.
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Stumped
Well today I unhooked the choke, change no filters found one hose that needed to be blocked off. Let her warm up before going to work, no problems. After leaving work, of course hard starting, drove home using same route no problems. I think I am going to put on manual choke. I sure hope this is it. I just hope the temp today wasn't a factor as today was the coldest it has been since I bought the pickup. All you'r ideas were much appreciated. And will keep in mind. I do like the idea of drilling out the fuel filter and having a inline, thanks.
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Stumped
I was experiencing a starvation under load and traced it to connecting hoses at the fuel tank selector valve being split and allowing air into the line when a big demand was placed on it, starving the carb for fuel. Check your hoses
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This is a long shot but......
I am running a 351M with a points dist for a 460. During the summer and warm weather about every 3 mos. my truck won't run for squat below 2000 rpm. My problem is the points go out of adjustment. Once regapped it runs fine. The only reason I bring this up is can't be the only one out there to have converted an electronic iginition engine to points.
I am running a 351M with a points dist for a 460. During the summer and warm weather about every 3 mos. my truck won't run for squat below 2000 rpm. My problem is the points go out of adjustment. Once regapped it runs fine. The only reason I bring this up is can't be the only one out there to have converted an electronic iginition engine to points.
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Stumped
she has no points, but I have been driving around put a few miles on her with the choke unhooked. It hasn't given me any more problems. I am going to go with manual choke. thanks guys for all the help here. Hope I will be able to help now that I found the best Ford site with message, I will be reading on a normal base. One question, does anyone know of a site like this one for Harleys, I have one of those to and would like to share my ideas and recieve as this site. Thanks again.
Rollingthunder.
Rollingthunder.
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