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MG Midget and Sprite Technical - Measuring fuel pressure

Chaps

Any smart way of measuring fuel pressure into the carb?

I have a Facet pump, then a regulator - but would like to check what fuel pressure is actually being delivered to the carb.

I have a dial type tyre pressure gauge if it helps!
Oggers

You can buy Bourdon tube type gauges off ebay reading 1 bar for about £6 delivered so that might be an option to plumb one in, a U tube manometer with water in it would need to be about 3m high to measure 4psi.
David Billington

Agreed David. The manometer was what I was thinking of also - but filled with oil instead so as to reduce the length.
Oggers

The problem there is that oil is less dense than water so you would need a taller U tube.
David Billington

Malpassi, who make a fuel regulator (as well as their well known Filter King), do a fuel pressure gauge that goes inline after the pressure regulator. Styec do too. Note there is a carb version and a fuel injection version.

https://www.glencoeltd.co.uk/catalogsearch/result/index/?cat=26&q=Fuel+gauge

Cheers
Mike
M Wood

I use the 0-15 psi Sytec gauge, it just screws into the Filter King body. Only used it once then removed it and fitted the brass blank.
John Payne

Good point David! Mind the stuff I pump from under the sea often feels like it is not.....
Oggers

Oggers. Do you intend to install a full time fuel pressure gauge or simply verify the accuracy of your pressure regulator as a one off? Full time, simply install a T fitting in the line from the fuel filter (in case the filter has any impact on the pressure) and carbs, then hook up a gauge to it. Good thing for the gadget minded individuals who like the interior of their car to look like the cockpit of a jet fighter.

My own experience has been that simply setting the regulator up with a pressure gauge at the end of the line that would normally go to the carbs has been sufficient for my needs. Thus, set the regulated pressure (if it actually needs it--sometimes it does not depending on the fuel pump used), remove the gauge from the line after the pressure is set, reconnect it to the carbs, enjoy life.

Plumbing in the gauge, on a permanent basis, is simply one more system that may, and sometimes does, go wrong. I can drive a modern car if I want excessive levels of complexity. Simplicity, resulting in being able to work on the vehicle without tens of thousands of dollars of test equipment, is why I keep driving these cars and have for over 50 years. Les
Les Bengtson

Les

It will be a one off. The engine is fitted with bike carbs which operate at less fuel pressure than the pump delivers. Just want to check what it is, adjust if required, then disconnect.
Oggers

If you don't know what pressure the bike carbs will take (usually gravity fed) then you have no known value to set the reg. to anyway
I'd just adjust up one click at a time till the pressure overcomes the needle/seats then go back one click- and then pull a hose off and check the volume at that setting
For a setup like that I'd be looking for something like 150-200ml minimum in ten secs
William Revit

This thread was discussed between 14/10/2020 and 19/10/2020

MG Midget and Sprite Technical index

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