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Mechanical Fuel Pump/Fuel Pressure question
Posted by: guthrie1068 ()
Date: July 12, 2022 09:26AM

My car has a mechanical fuel pump on it with a pressure gauge in line at the pump. Last year it was running around 6psi, but this year when I fired the car it was around 9, and has been climbing. This morning it was at 14psi, and leaking around the bolts in the housing. I know 6 is higher than I'd like, and 9-14 is a problem, but I can't figure out why it happened. I'd like to fix it instead of just buying another one.
I also know that I can buy the adjuster kit for the pump, but if I can make a simple repair I would prefer to do that. Any ideas?

Chad Guthrie
Rives Junction, MI
'63 convertible

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Re: Mechanical Fuel Pump/Fuel Pressure question
Posted by: Frank DuVal ()
Date: July 12, 2022 10:20AM

No idea! The pressure is made by the internal fuel pump spring, nothing else.

The pump is before the gauge, right? The gauge is in the lines going to the carburetors?

Frank DuVal

Fredericksburg, VA

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Re: Mechanical Fuel Pump/Fuel Pressure question
Posted by: MattNall ()
Date: July 12, 2022 10:22AM

This is unusual! The spring controls pressure and coil springs get weaker, not stronger, with age.

Take it off, dismantle and clean. Tell us what you find.

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
...............110-PG.................................................Webered-Turbo

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Re: Mechanical Fuel Pump/Fuel Pressure question
Posted by: guthrie1068 ()
Date: July 12, 2022 10:38AM

Correct, the gauge is in the T, between the pump and the carbs.
I'll pull it apart and take a look.

Chad Guthrie
Rives Junction, MI
'63 convertible

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Re: Mechanical Fuel Pump/Fuel Pressure question
Posted by: Brizo ()
Date: July 12, 2022 11:46AM

its more likely the gauge is weakening . ?

Dan Brizendine, Circle City Corvairs
'64 8 door Greenbrier, +.060, stroked 1/4", 186 ci.140 PG. "In beautiful Wanamaker Indiana...with one stop light and 5 pizza shops"

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Re: Mechanical Fuel Pump/Fuel Pressure question
Posted by: guthrie1068 ()
Date: July 12, 2022 11:53AM

I also wondered about the gauge, but the car didn't want to run this morning and I think it is fuel pressure related. I haven't pulled the air cleaners off to see if fuel is dripping in the venturi, but I will get to it.

Chad Guthrie
Rives Junction, MI
'63 convertible

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Re: Mechanical Fuel Pump/Fuel Pressure question
Posted by: azdave ()
Date: July 12, 2022 05:38PM

My testing showed softness/hardness of the diaphragm material plays a part in the pressure achieved. I can get 2-3 PSI on some pumps with the cap spring completely removed. I also saw the pressure fall a bit while driving as the pump became warmer. I attribute that to the diaphragm getting more supple. It was not enough change to worry about but was observed multiple times.

Dave W. / Gilbert Arizona
65 Corsa 140/4
66 Corsa 140/4
66 Corsa 140/4 w/factory A/C
66 Corsa 455 Toro V8
65 Monza Convertible 110/4
66 Monza Convertible 140/4 A/C
65 Monza 4DR 140/PG w/factory A/C
65 Monza 4DR EJ20T/5



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