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Lemons 4 Gigi
Samba Member
Joined: May 18, 2020
Posts: 89
Location: Slidell, LA
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 Posted: Fri Apr 09, 2021 12:10 pm Post subject: Lowering fuel pump pressure... |
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Is stacking gaskets the preferred method of lowering fuel pump pressure? Has anyone experienced problems in fuel delivery at high speeds that have used this method?
My new "no name" pump is putting out over 4 lbs causing flooding after I shut off my engine. I can clearly see the fuel fill up the carb throat after I turn off my engine thus leaving me in a hard start situation...
Thanks!
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1971 Super Convertible "Gigi", Lemon Yellow (Factory Zitronengelb L-11E)
1970 Dodge Challenger R/T "Jezzy", 440, 4-spd, pLuM cRaZy!
A couple of Jeeps.. |
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pwmcguire
Samba Member
Joined: January 30, 2011
Posts: 1108
Location: Kennesaw GA
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| Posted: Fri Apr 09, 2021 12:38 pm Post subject: Re: Lowering fuel pump pressure... |
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No this changes volume, I have never had any success doing this. Yet people will
say to do it any how. |
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74 Thing
Samba Member
Joined: September 02, 2004
Posts: 7391
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| Posted: Fri Apr 09, 2021 12:39 pm Post subject: Re: Lowering fuel pump pressure... |
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| Yep, volume vs pressure. |
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busdaddy
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Joined: February 12, 2004
Posts: 51144
Location: Surrey B.C. Canada, but thinking of Ukraine
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Eric&Barb
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Joined: September 19, 2004
Posts: 24757
Location: Olympia Wash Rinse & Repeat
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VW_Jimbo 
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Joined: May 22, 2016
Posts: 9966
Location: Huntington Beach, CA
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| Posted: Fri Apr 09, 2021 2:48 pm Post subject: Re: Lowering fuel pump pressure... |
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If you need to reduce pressure, you will need to use a pressure regulator. Holley 12-803 or 804, I think. They have a range of 1 - 4psi.
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kreemoweet
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Joined: March 13, 2008
Posts: 3898
Location: Seattle, WA
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| Posted: Fri Apr 09, 2021 4:32 pm Post subject: Re: Lowering fuel pump pressure... |
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Fuel pump gaskets have only insignificant effect on output pressure. Adding gaskets could also reduce output volume, since they
reduce the maximum possible output stroke by the thickness of the gaskets, but maximum stroke only occurs in extreme
circumstances, such as turning engine over with starter with an empty float bowl and perhaps at very high rpm's if a large
number of them have been used.
Modifying the diaphragm spring is the most direct and effective way to affect pressure, but one might as well
just get a correctly made pump in the first place.
4 psi is well within the fuel pressure spec for the stock carb on a '71, so I do not think that is your problem.
There is no more pressure made by the pump when the engine is shut down, and it can not cause "flooding"
of the carb bowl. It sounds like you have gravity flow to the carb, due to a bad needle valve in the carb or the
lack of a fuel cutoff valve, which was stock on carbed VW beetles since the early sixties.
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Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 24757
Location: Olympia Wash Rinse & Repeat
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| Posted: Fri Apr 09, 2021 5:00 pm Post subject: Re: Lowering fuel pump pressure... |
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We have also in warm weather had fuel drip in the carb after shut down. Added a second gasket to the float shut off valve and that solved our flooding troubles.
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Lemons 4 Gigi
Samba Member
Joined: May 18, 2020
Posts: 89
Location: Slidell, LA
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| Posted: Fri Apr 09, 2021 5:04 pm Post subject: Re: Lowering fuel pump pressure... |
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Yeah, that was my first guess... You get what you pay for.
Thanks All for the feedback. Much appreciated!
_________________
1971 Super Convertible "Gigi", Lemon Yellow (Factory Zitronengelb L-11E)
1970 Dodge Challenger R/T "Jezzy", 440, 4-spd, pLuM cRaZy!
A couple of Jeeps.. |
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Lemons 4 Gigi
Samba Member
Joined: May 18, 2020
Posts: 89
Location: Slidell, LA
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| Posted: Fri Apr 09, 2021 5:33 pm Post subject: Re: Lowering fuel pump pressure... |
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| kreemoweet wrote: |
Fuel pump gaskets have only insignificant effect on output pressure. Adding gaskets could also reduce output volume, since they
reduce the maximum possible output stroke by the thickness of the gaskets, but maximum stroke only occurs in extreme
circumstances, such as turning engine over with starter with an empty float bowl and perhaps at very high rpm's if a large
number of them have been used.
Modifying the diaphragm spring is the most direct and effective way to affect pressure, but one might as well
just get a correctly made pump in the first place.
4 psi is well within the fuel pressure spec for the stock carb on a '71, so I do not think that is your problem.
There is no more pressure made by the pump when the engine is shut down, and it can not cause "flooding"
of the carb bowl. It sounds like you have gravity flow to the carb, due to a bad needle valve in the carb or the
lack of a fuel cutoff valve, which was stock on carbed VW beetles since the early sixties. |
Thanks for this. I've added a gasket to the needle valve to lower it and cleaned it out real good. I also just replaced the older steel fuel line that's routed in the engine compartment since I relocated my filter (should have been done while I was restoring her). When I removed the top of the new carburetor, I noticed small rust particles that I contribute to the older fuel line and no filter to catch it. I think I'll run her at the current 4 psi and see if it was the stuck valve allowing the fuel to overfill the bowl. Afterall, when shut off, it would take 15 - 20 seconds until you see the stream coming out of the emulsion tube.
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1971 Super Convertible "Gigi", Lemon Yellow (Factory Zitronengelb L-11E)
1970 Dodge Challenger R/T "Jezzy", 440, 4-spd, pLuM cRaZy!
A couple of Jeeps.. |
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Eric&Barb
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Joined: September 19, 2004
Posts: 24757
Location: Olympia Wash Rinse & Repeat
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| Posted: Fri Apr 09, 2021 5:47 pm Post subject: Re: Lowering fuel pump pressure... |
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Also could be the float is just too heavy.
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Floating VW
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Joined: April 28, 2015
Posts: 1597
Location: The South Zone
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| Posted: Sun Apr 11, 2021 10:57 am Post subject: Re: Lowering fuel pump pressure... |
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| Lemons 4 Gigi wrote: |
| Thanks for this. I've added a gasket to the needle valve to lower it and cleaned it out real good. . . |
Be careful, changing the float height can also change the air/fuel ratio of the carburetor, especially under partial-throttle conditions.
Adding gaskets under the needle valve might solve one problem, but create another.
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