RowJ

Anyone tested their needle valve to see if they can shut off fuel flow to mech. FP gauge?

My ISSPRO gauge has been acting up..jumpy and starting to make noise. I tried totally closing off needle valve to prolong gauge life. Still got FP reading?? It had some crud on it so took it off, cleaned it, fluid tested it (not under pressure) to be sure it closed all the way...and reinstalled.

Appears that, when under 15 psi pressure, needle valve will NOT block flow to gauge! At least mine won't.

Good news is, shut full off, gauge no longer jumps/rattles...and I can't remember ever hearing of anyone recently having a leaking gauge.

Anyone else ever tested their fuel shut-off?

RJ

mysing418

You have a mechanical gauge isolator inline or is it straight lined in to the gauge from the needle valve?

I did my plumbing with an inline 1/4" brass ball valve instead of a needle valve. It will be on or off with a 45 degree twist. I mounted a mechanical gauge isolator on the firewall filled with antifreeze on the gauge side as per instructions and no problems for 2+ years...

Bluedeviltorque

RJ,

I have noted that the same thing happens with my gauge set-up. Even if I crank the needle valve closed tight I still get a nice smooth gauge movement. The gauge also reads the same pressure as it does if I open it up a few turns.

On a side note, I have never experienced the gauge rattle that many have described. Maybe I'm just lucky with my autometer gauge.

Mike

RowJ

Yes, I have a T in my 1/4" fuel line to a needle valve...reduced to 1/8" line direct to gauge. Your system sounds great...live & learn.

Found interesting info on another thread reguarding TST fuel line valve which flows VERY small amount of fuel - hole less than a human hair. Seems thats all that's needed, since there is no flow.

See here...https://www.dieseltruckresource.com/...887#post535887

Guess it's not suprising after all that needle valve won't shut down gauge! Thought this info was worth sharing in case others had same misconception.

RJ

Shovelhead

Interesting.
When I fire mine up, shut my needle valve off, then shut off the engine, I still see 16 psi.
And when I open it enough to bleed off the pressure, then shut it off, and fire the engine, I don''t see any reading until I crack the valve open again.
Must be using a different needle valve.

infidel

Seems like Ed's is working perfectly, trapping the pressure change down stream of the valve.
Makes me wonder if that's what the rest of you are seeing also.
Will the gauge climb up from zero if the valve is closed?

I've installed dozens of these valves but had never had a reason to shut one off completely, no leaks. But on the initial adjustment have been able to freeze the gauge reading when running to the same with the engine off by closing the valve while running.

RowJ

Mine is a 1/4" valve...as stated above.

I reinstalled my needle valve fully closed and started it up. Got bump & back to zero with key on...Got fuel pressure reading just like before gauge started singing and dancing! Goes to zero on shut down???
Maybe did not get valve totally clean...it was pretty dirty. Good to know they should work under pressure!

RJ

mysing418

I bet on a bad needle valve RJ. As far as the rattling gauge... the fuel line to the gauge is filled with fuel causing a hydraulic lock hammering on the gauge. Like in some houses when you turn the water off too quick it causes a hammering noise in the pipes. Need to bleed the fuel out of the gauge line an it'll quieten up and act right. The gauge needs an air cushion to work right. Really for safety sake too put on an inline gauge isolator or you might get an eye full of diesel fuel if the gauge lets go.

dodgediesel4x4

My needle valve will shut off the fuel supply to my fp gauge, making it read zero. I don't have an isolator, just running it from the back of the fuel canister and into the cab. Hope that threadlock works, but 8 months later, no leaks.

MARKY MARK

This is what my needle valve does. I start the motor and then shut off the valve and pressure stays the same on the guage. But if I shut the motor down with the valve on, then shut off the valve and start it up...I have no pressure until I open the valve.

Rain Man

I know from my expenience as a plumber that you need to exercise valves occasionaly to keep the seating surfaces clean and free from buildup. This could, and probably should, be done at oil change times as a matter of routine maintenance.

Moose10

Same here Marky Mark. If I close the valve, start the engine, I'll have 0 on the gauge 'til I crack the valve open.