tywebb3

I want to try removing my fuel pressure isolator to see if it affects the reading on my fuel pressure gauge. I have a needle valve attached to the bottom of the fuel filter canister which now runs to the isolator. Can I just connect the line from the needle valve to the back of the gauge to see what it reads? Is there any way to bleed this once connected? I am going to do this leaving the gauge in the engine compartment just to see what happens. The truck runs great but I have been getting readings of between 0-2psi on the gauge and it just isn't adding up?

mishkaya

I have been running my fuel pressure gauge the way you described for over 6 years now with no issues. Some gauges don't take too kindly to diesel however....
You can bleed the gauge by loosening the fitting at the gauge with a paper towel around it to catch the trace of diesel coming out. Of course you will want to make sure the needle valve is just barely open....

tywebb3

I have an Isspro gauge if that makes any difference?

kreynolds

I've been running my issopro that way for about a year. I bled my line by bumping the starter to get the pump running. Cracked open the needle valve and let the line fill up with fuel then closed the needle valve. Hook up the gauge then open the valve back up. A little air in the line won't hurt anything. With the pump running the line will fill up fast so you only have to open the valve a little bit.

67HotRod

I would try another gauge, connected at the vp44 inlet.
That low of fuel pressure might cost you a new vp44.

kreynolds

I ditched my isolator because I was getting inconsistent readings. With a new lp, pressure would start around 15 then steadily drop over several miles. Removing the isolator is a cheap and easy method to eliminate it as a problem source. You should be able to quickly and easily tell if the isolator is your problem before any damage is done to the vp.

mishkaya

ISSPRO is what I am running as well, so you should be good!

Junk Man

ISSPRO with no isolator also. I closed the needle valve completely. Then started engine and opened the valve a little at a time until I got a reading. Apparently, bleeding took care of itself. Mopar1973man posted a video of how he thinks the needle should move (slowly) on start up. My needle valve won't adjust to get that response but gauge is still working at 40,0000 mi. FP = 13-15# even under load.

infidel

16 years in two trucks with no isolators and no problems.
After about ten years I went to replace one gauge for a nicer one I had found and got all prepared for diesel in the cab.
Not one drop of fuel, I could see though the clear nylon tube that it was still full of air after ten years.
Gauge read just fine, no need to bleed.

One problem if I'm not mistaken though is the bottom of the fuel filter is the inlet/dirty side of the filter.
To get a good reading you need to be on the clean side of the filter.

tywebb3

Well....the isolator was the problem. I took it out and put a simple union in its place tonight and what do you know, the gauge went right to 18.5psi.....where it used to be when I initially installed it years ago. Guess I'll just run it without the isolator now

nkennedy

Isolators give a lot of faulse gauge readings. I work in insturmentation, and we just find a gauge that will stand up to the fluid being measured.

Junk Man

You want a needle valve to damp the LP pulses and provide a method of shutting it off if necessary.