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Adjusting mechanical fuel pump pressure.

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Adjusting mechanical fuel pump pressure. #1
wesleygarrard wesley garrard Pekin, IL, USA Sign in to contact 1963 Volkswagen Beetle "Herbie" 1979 MG Midget 1500 "Pete"	Topic Creator (OP) Mar 1, 2015 10:43 AM Joined 11 years ago 269 Posts

We are switching back to a mechanical pump on Whitney's midget and I have heard that some pumps put out more pressure than factory specs. If the one we ordered produces too high a pressure, I would like to be able to adjust it.

In the Aircooled VW world, we adjust the fuel pressure on the mechanical pumps by stacking gaskets under the fuel pump. This works very well. Would it also work on the 1500? What are your thoughts?

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Re: Adjusting mechanical fuel pump pressure. #4
TeamEvil Thomas C (Disabled) Kingston, MA, USA Sign in to contact	Mar 2, 2015 01:52 PM Top Contributor Joined 12 years ago 5,815 Posts

The Beetle pump operates with a rod, easy ti adjust with shims or gaskets. The MG pump operates with a lever riding on a lobe, it's pre-set. extra gaskets or shims will just pull it further away from the lobe.

The lever is stamped steel and pretty much non-adjustible, a fuel pressure regulator (a GOOD one, NOT the chromed circular piece of crap !) would be the best way to go.

SU and Weber carbs can be very sensitive to fuel pressure, a Solex doesn't know or care as long as the float bowl is full, accelerator pump functional, and inlet jet not sticking. Most Solex carb problems are caused by an 009 distributor swap.

Solex carbs are like dumb dogs, just want to be loved and exercised three of four time a week.

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Re: Adjusting mechanical fuel pump pressure. #5
wesleygarrard wesley garrard Pekin, IL, USA Sign in to contact 1963 Volkswagen Beetle "Herbie" 1979 MG Midget 1500 "Pete"	Topic Creator (OP) Mar 2, 2015 02:17 PM Joined 11 years ago 269 Posts

In reply to # 2931284 by TeamEvil The Beetle pump operates with a rod, easy ti adjust with shims or gaskets. The MG pump operates with a lever riding on a lobe, it's pre-set. extra gaskets or shims will just pull it further away from the lobe.

The lever is stamped steel and pretty much non-adjustible, a fuel pressure regulator (a GOOD one, NOT the chromed circular piece of crap !) would be the best way to go.

SU and Weber carbs can be very sensitive to fuel pressure, a Solex doesn't know or care as long as the float bowl is full, accelerator pump functional, and inlet jet not sticking. Most Solex carb problems are caused by an 009 distributor swap.

Solex carbs are like dumb dogs, just want to be loved and exercised three of four time a week.

The Solexes are quite good. I run twin 34PDSIT Solexes on my Beetle. But I use an electric pump on it.

On the Midget, I have adapted twin Mikuni BS 38 carbs and I am having overflow issues with both the Purolator pump and Holley Blue pumps I had laying around, even with a good Quick Fuel 1-3psi regulator. Currently with the Holley pump, even though the gauge reads 1.5psi, I am having overflow issues. Could be due to the large volume of fuel that the Holley pushes. I thought I would try a mechanical pump that would be more suited to the pressure and volume that the carbs would need. It is good to know that the pressure on a mechanical pump can be adjusted with a regulator.

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Re: Adjusting mechanical fuel pump pressure. #6
capnkx nathan c Albuquerque, NM, USA Sign in to contact 1979 MG Midget 1500	Mar 5, 2015 01:59 AM Joined 12 years ago 633 Posts

Even with two gaskets my pressure would creep to 15 and stall while idling hot. With Holley regulator. Added a bleed return at the carb and solved heat soak and excess pressure in one go. Use a vented gas cap and then use the vapor line as a return. Eliminate the charcoal canister of course.
If the fuel boils in the line you'll never get the pressure where you want it

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sprout1960 russel riley preston, lancasher, UK Sign in to contact	Mar 2, 2015 12:19 PM Joined 9 years ago 18 Posts

Re: Adjusting mechanical fuel pump pressure. #3
zippy brian j vista, CA, USA Sign in to contact 1966 Austin-Healey Sprite 1971 MG Midget MkIII	Mar 2, 2015 01:38 PM Joined 10 years ago 260 Posts

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