Checking fuel pressure

Does anyone have a simple idea on how finding out what your fuel pressure is?

Many thanks!--Jack

Pull carb fuel inlet line have someone "key on" as you aim the hose into a coffee can looking for a good strong squirt-stream...not the most accuate method but gives you a visual check.

Thanks Alan. I am considering some new carbs and need some kind of a psi number to check compatability. My engine has the stock '72 mechanical fuel pump--is there a standard pressure delivered by these pumps?---Jack

3psi

for under 30.00 bucks you can buy a fuel pressure tester to eliminate the guess work. The one I have tests vaccum as well. I'm running a set of tweeked Kadron's which as I was told run best at 1.5 to 2 psi and they do. A lot different then the 3.5 to 4 psi I had on the Webbers. Also you can change the fuel pressure some with the thickness of the gasket under the pump or go regulated electric.

victor

They make gauges that do this. All the hot-rod guys seem to love to put these on. I am guessing you could get one to read down at these levels. You could also make a manometer, which is to say a long clear tube of any diameter running vertically. By my calculations, if your pump puts out 3 psi, then it will support a column of gas about 9.8 ft high. You could hook this tube up to the system, and with the pump off, you may notice if gas runs into the tube, and where it settles. All things being equal, it should find the same level as the gas currently in your tank. All things may not be equal, since the system may have a check valve in there somewhere, so maybe no gas will come out. If you see gas, call that zero; if not, call the pump location zero. Turn on the pump and see how high the gas goes up the tube. (This will be hard if pump is mechanical, as you will need the engine running. The make-shift manometer would then have to be T-ed in to the line, so gas goes to the carbs too.) With total height at 3 psi of 9.8 ft, you will have plenty of accuracy w/ a tape measure to read out the pressure. This is based on assuming gas is 0.7 grams/cubic centimeter density (water is 1.0 gm/cc, BTW). I think I'd buy the gauge.

PS: tube does not have to be straight, just has to have an opening comfortably higher than ten feet, and open at the top. Furthermore, if your neighbors see you doing this, they will rightly believe you have lost your mind.

Kelly--thanks for your idea but I'm certain I could never pull this together! Kudos to you for smarts though!!

Anyone---can you tell me where to but a simple accurate fuel pressure tester with proper connections, etc?

Many thanks to all---Jack

Jack, Your stock pump will work well with any carb you pop on top of the manifold.
The issue with carbs (the cheaply made newer types) is that they have trouble holding
back more than 4 psi at the float needle. If you have no trouble now you won't after your mod. I've said this before but sometimes people get flow and pressure mixed up. You carb is like a toilet tank. Your pump only fills the bowl(tank) like your water supply. After that the fuel/water pressure has little to do with the operation of the fuel ingestion(flush). It only refills what is used. A stock (read german) pump is hard to beat.

Why not just buy one of the EMPI fuel pressure regulators for $20 from CIP1? They seem to be accurate and easy to twist a dial to adjust pressure. Weber carbs seem to be fussy and require 3.5 PSI.

I'm going to invite Kelly over, and then I'm going to sit back with beer and popcorn.
My report on his activities will not be nearly as technical.

I've been warned that the dial type fule pressure regulators are not real accurate. Go a few extra bucks and buy a screw type regulator with a gauge built in. I like Holley myself, but there are others. A dial regulator without a gauge backup may not solve anything - says my local hot rod supply - and they sell BOTH types.

You may want to consider buying a high quality electric rotary fuel pump that's calibrated to 3.5 PSI.
I've been running a Pierburg with great success for the past two years.

Check out Bus Boys website: http://www.bus-boys.com/bb13386.htm