low fuel pressure?
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Joined: May 2012
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low fuel pressure?
I have a 66 F100 with a 300 cu. in. from a 1975 in it. It runs fine for the most part, with one annoying problem: I mounted a gas tank between the rails under the bed in the rear, as the one behind the seat was pretty much beyond saving when I bought the truck. A tank from an old Chevy Blazer fit up there pretty well. It seems though that I have low fuel pressure, especially when the tank gets even half empty. It will stumble and starve. I installed an in--line pressure guage up near the carb and sometimes when it's acting up it is fluttering slightly at around 3 PSI, which I know is low. The line has been blown out, the filter changed, and the sending unit seems fine. If I fill the tank with fuel, it helps, for a while. I wonder if the pump is a little too weak to pull the fuel that distance and if I should try an electric pump. Anyone offer any advice?
Lead Gopher
Joined: Aug 2012
Posts: 10,080
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From: Seattle
I've found electric fuel pumps to be noisy and not overly reliable since they often use the fuel to cool the pump.
One thought would be to try a new, fresh mechanical pump.
But, if you have good pressure when the tank is full and not so good as it starts to empty it sounds like the pump might be OK.
Any chance the gas tank should be vented but you have a non-vented cap on it? Once a suction builds up drawing more fuel would start to become more difficult and pressure could drop down some. It might still get a tiny bit of air coming in and so it doesn't completely starve but gets close to it?
Just a thought from outside the box.
One thought would be to try a new, fresh mechanical pump.
But, if you have good pressure when the tank is full and not so good as it starts to empty it sounds like the pump might be OK.
Any chance the gas tank should be vented but you have a non-vented cap on it? Once a suction builds up drawing more fuel would start to become more difficult and pressure could drop down some. It might still get a tiny bit of air coming in and so it doesn't completely starve but gets close to it?
Just a thought from outside the box.
Post Fiend
Joined: Dec 2013
Posts: 5,967
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From: Philly Suburbs, PA
sorry. didn't pick that up.
Cargo Master
Joined: Apr 2003
Posts: 2,389
Likes: 58
What is the pressure when it is running right?
The ford sending unit operates at a different resistance range than the Chevy, right? Could it be possible that the tank is actually empty even though your gauge is indicating there is still fuel left?
The ford sending unit operates at a different resistance range than the Chevy, right? Could it be possible that the tank is actually empty even though your gauge is indicating there is still fuel left?
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