Malpassi fuel regulator

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peterc
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Malpassi fuel regulator

Post by peterc »

You may possibly be aware that I had a problem leaving the Silverstone Classic resulting in being rescued by the AA and re patriated over night to home.
I have spent quite a few hours investigating why the fuel pump was not doing its job and not finding an answer to the problem.
Finally removing the filter bowl on the Malpassi regulator fitted in the engine bay I discovered that the regulator valve was laying down inside the filter element and not in its correct position against the diaphragm.
Yes, this must be rather unusual for this item to fall apart but BGC says they have heard of it happening before.
So suggestion that when checking the lack of fuel in the carb perhaps you should check the filter bowl first before delving deeper resulting in un necessary work.
Remember if you take the filter bowl off it’s most likely the two seal rings will drop out so be prepared.
I have managed to re assemble mine and surprised how tight a fit the plastic retaining Bush was to push back in but by then I had made the decision to not take chances and ordered a new one.

Peter C
Last edited by peterc on Mon Sep 12, 2022 8:45 pm, edited 1 time in total.
cobraboy
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Joined: Mon Jul 26, 2021 6:50 pm

Re: Malpassi fuel regulator

Post by cobraboy »

This may be a crazy coincidence, but I can assure you that it is totally true.
Last Sunday my Cobra failed to proceed on the way back from a show. I started out with 3 gallons in the tank, 1 gallon there, 1 gallon home, 1 gallon spare, plus I took a 2 gallon can in the boot.
The reason for running light in the tank, I do not know if I will take the car to Goodwwood, if not I don't want a full tank of fuel going 'off'.
Anyway I cornered hard round a long bend, the fuel surged away from the pickup pipe, the pump sucked air and would not re prime.
By putting in the 2 gallons from the can, taking apart the pipework, sucking on the outlet from the pump, I managed to get it to pull fuel, and I made it home.
In the garage at home it was idling roughly, I looked at the pressure gauge on the filter king and it showed 8 psi, Hmmm.
Backing off the adjuster screw on the top made no difference, in fact I removed the screw and it still showed 8 psi.
I took off the bowl and looked in the filter and there was the brass regulator needle, a spring, and the plastic retainer !

To fix it I put the plastic retainer in my lathe and turned it down around 1mm, I re assembled the gubbins, pushing the plastic retainer further in than before, allowing for its reduced length, this allowed me to stake the bottom of the alloy housing with a chisel, that bugger ain't coming out again!
I have heard the motorsport community don't rate the Filter King, I now know why.
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peterc
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Re: Malpassi fuel regulator

Post by peterc »

I have not modified the plastic retainer but did center pop the edge of the bore in four places to ensure a tighter fit. Still surprised it could come out in the first place. Yes the pump can create a lot more pressure than the 5.5 psi needed it must need a fair bit to push the retainer out.
Peter C
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