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Re: [TR] What is the correct way to measure fuel pressure

To: "'Sujit Roy'" <>, "'Triumphs'" <>
Subject: Re: [TR] What is the correct way to measure fuel pressure
From: "Randall" <>
Date: Mon, 21 Oct 2019 14:12:04 -0700
References: <>
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Don't forget to account for the difference in height between the pump and
carbs.  The spec in my book is 2.7 psi measured at the pump; and if I've
done my math right, each 3.75" rise will reduce that by 0.1 psi.  So
assuming the carbs are about 2' above the fuel pump, you should see closer
to 2 psi at the carb inlets.

But I don't trust measuring tools from HF, especially used ones.  Check it
with another gauge; or if you don't have one, build a simple manometer.  A
6' length of pipe or tubing could make a simple "go/no-go" gauge; hold it
vertically and if the pump can push fuel out the top, you've got enough fuel
pressure.  Or for temporary use, some cheap vinyl tubing from Home Depot
tied to a piece of wood will let you read the height.  Vinyl isn't rated for
fuel of course, but should do for a quick test.  (Don't use it for anything
else afterwards, though.)  37.4" should equal 1 psi of gasoline (using
numbers I got from Google).

Not at all relevant, but the book also calls the pump "high pressure", which
I find amusing.

-- Randall 
56 TR3 TS13571L once and future daily driver
71 Stag LE1473 - awaiting engine rebuild
71-2-3 Stag - awaiting gearbox rebuild 

> I borrowed a Harbor Freight fuel pressure gauge from a fellow 
> Triumph owner. I disconnected the supply to the ZS carbs and 
> connected the pressure gauge directly to the feed.
> The gauge read less than 1 PSIG. I have a Stag and it is 
> using an SU electric fuel pump.The stag pump should be around 3 psi. 
> Am I measuring the pump correctly? Should I Tee in the gauge 
> inline with the carbs instead?

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