fuel pump losing prime ?
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fuel pump losing prime ?
I have a M151 A2 that loses it's prime if it sits for and hour. I have to pour gas in the carb intake. It has done this for a long time. I've put a new fuel pump on and it still acts the same. Does anyone have a suggestion???????? TJ
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Re: fuel pump losing prime ?
This is a very expensive way of doing things. Also good reason to diagnose properly & not just replace good parts with other good parts.Tom wrote:I've put a new fuel pump on and it still acts the same.
Testing/checking the original fuel pump would have ruled it out as the problem & even though you have a new one you should check it. Vacuum/pressure gauge from HF about $15 is a good investment.
Any kind of fuel pump relies on pressure differentials to operate.
If you don't have these differentials you have a problem like yours.
Unless the fuel pump is an in tank type, you will no doubt find there is an air leak caused by loose union/s or leaking gasket/s between the fuel tank & fuel pump.
This will not necessarily show as a fuel leak @ any potential leak point & usually doesn't.
It will show if you low pressurize the fuel tank then check right to the fuel pump for fuel leaks or dampness. Then repair each one.
Leaks after the fuel pump will dangerously show, if the engine is running [potential engine bay fire] & will not cause what you call loss of prime.
Last edited by artificer on Tue Jan 26, 2016 11:04 am, edited 1 time in total.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.
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Re: fuel pump losing prime ?
Are you using the choke and does the choke close all the way? Without a manual accelerator pump to inject gas before you start you have to use the choke to start a lot of the time even when hot. Also make sure the intake hose from the carb to the air cleaner is left on, if not you lose the last shot of gas that is injected into the carb throat as it shuts down. There are one way valves in the fuel pump to prevent gas from running back to the tank but that would not cause the problem you are having since the carb bowl holds more than enough gas to start the engine and keep it running long enough for the pump to pull gas from the tank. The pump draining back will not drain the carb bowl.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: fuel pump losing prime ?
Gentlemen, I thank you for the interesting comments. That gives me much to think about and diagnosing to do. I'll be getting on it soon. Thanks, TJ
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