1979 with 400 engine starts and runs then runs out of power.
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6th Gear
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1979 with 400 engine starts and runs then runs out of power.
I have a old truck recently got a new fuel tank and new lift pump. Starts and runs goodbut once you get driving down the road seems to be lacking in power. Feels like the engine is going to die when you push the pedal to the floor. It has a four barrel carburetor.
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it has a 1408 edelbrock carburetor
Last edited by Lodermeierbr; May 8, 2023 at 09:20 PM.
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6th Gear
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I don't think edelbrock have power valves do they? I recently replaced fuel filter and blew out the lines did not seem to help any. This is a manual transmission 1rst and 2nd gear does not seem to bother when I shift to 3rd and 4rth then the motor kind of chugs along.
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From: Angier, NC
I am pretty sure even if it had a PV and if it was leaking it would only run rich and not lack power.
I am guessing the truck has been sitting a long before you got it if you changed the tank & lift pump?
How long has it been sitting?
Where is this lift pump located in tank or motor?
Where is the tank on the truck, in cab, front side of bed or rear of bed?
When you replaced the tank did you also replace ALL RUBBER HOSES?
When you have been driving it the gas cap has been in place? If so remove it and try again.
Truck have a cat?
Dave ----
I am guessing the truck has been sitting a long before you got it if you changed the tank & lift pump?
How long has it been sitting?
Where is this lift pump located in tank or motor?
Where is the tank on the truck, in cab, front side of bed or rear of bed?
When you replaced the tank did you also replace ALL RUBBER HOSES?
When you have been driving it the gas cap has been in place? If so remove it and try again.
Truck have a cat?
Dave ----
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6th Gear
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Truck has sat for about 15 years in a shed. It has a mechanical pump located on the engine. We did replace all of the rubber lines when installing a new tank. The tank is located under the the bed left front side.
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From: Angier, NC
15 years is a long time.
Did you rebuild the or replace the carb?
What carb is it a factory v2 that I think would be a 2150?
Good you tried the no cap trick. Bad that it was not the issue
You did not say if the truck has a cat?
What I am thinking is a plugged exh system.
It maybe the cat as the honey comb is small and any rust & carbon from upstream could plug it.
Also if a mouse got in the tail pipe it could have made a home and plugged it.
What happens is it may not be totaly plugged and as you drive the system builds up psi and when you get into the higher gears to psi is to great and kills the power. One way I know of testing is using a vacuum gauge.
The other is to drop the exh system before the cat or muffler and go for a test drive.
That is all I can think of ATM
Dave ----
Did you rebuild the or replace the carb?
What carb is it a factory v2 that I think would be a 2150?
Good you tried the no cap trick. Bad that it was not the issue
You did not say if the truck has a cat?
What I am thinking is a plugged exh system.
It maybe the cat as the honey comb is small and any rust & carbon from upstream could plug it.
Also if a mouse got in the tail pipe it could have made a home and plugged it.
What happens is it may not be totaly plugged and as you drive the system builds up psi and when you get into the higher gears to psi is to great and kills the power. One way I know of testing is using a vacuum gauge.
The other is to drop the exh system before the cat or muffler and go for a test drive.
That is all I can think of ATM
Dave ----
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6th Gear
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There was a lot of mice in the exhaust it does not have a catlic converter. But could be plugged in the muffler ? It's a 1979 f250 and have a edlebrock carburetor on it that was rebuilt. I have owned the truck since 2005. It just starts and runs to good for it to seem to be carburetor trouble. I think I am going to look into the exhaust system.
More Turbo
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Could be a coil. Works when cold but fails as it warms up.
Edelbrock carbs have a power valve piston that uses a "step-up spring. Probably not that.
My bet is the accelerator pump. There have been problems with the acc pump plunger degrading from the fuel. It would start if it's using the choke, then when choke comes off the accelerator pump doesn't pump and you get a flat spot when you hit the throttle.
A plugged fuel filter acts like a power limiter, you can go the same speed max in all gears. it hits a speed and won't go faster.
Distributor mechanical advance has been known to stick and limit power. It starts good but engine has no guts above idle.
Good Luck
R.
Edelbrock carbs have a power valve piston that uses a "step-up spring. Probably not that.
My bet is the accelerator pump. There have been problems with the acc pump plunger degrading from the fuel. It would start if it's using the choke, then when choke comes off the accelerator pump doesn't pump and you get a flat spot when you hit the throttle.
A plugged fuel filter acts like a power limiter, you can go the same speed max in all gears. it hits a speed and won't go faster.
Distributor mechanical advance has been known to stick and limit power. It starts good but engine has no guts above idle.
Good Luck
R.
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