rockjeep73

well just got done installing my Isspro fuel pressure gauge with isolator, and not the results I was looking for. Ignition on - 10psi, at idle - 5-6psi, anywhere above idle - 2psi. So I guess im gonna be installing that FASS system this weekend thats been sittin in my room.

My questions are:
1) I hooked the gauge up to the schrader valve that goes into the injection pump (i took out the valve core), is this ok?

2) There are air bubbles in the line that goes to the gauge, im assuming this is fine and there is no way to bleed them out? Also, when I shut the truck off the gauge stays at like 2psi, is there still pressure in the system that slowly bleeds off, or should I unhook the gauge to allow it to drop to zero and then reconnect it?

Thanks in advance.

HOHN

Rock Jeep--

Sorry that no one responded to you sooner.

It's been my experience that isolators can cause screwy gauge reading under some conditions. I had a mechanical gauge that used an isolator. At some point, the the readings started showing 25-30psi-- with a completely stock fuel system (LP, banjos, etc.). The problem was my isolator. When I removed it from the system, the readings were normal and proper. I'm surprised my gauge wasn't damaged, because I found that the super-high FP readings were actually a severe suction-- the needle was being pulled lower than zero to where it went back around to the high side of the guage!

When I removed my isolator, I found that there was diesel all the way to the guage anyway. Meaning all that glycol that was in the line originally went through my VP44 and fuel system!! Not good.

So let me get to your questions:

1) Hooking it up to the Schrader is fine. Just make sure you use the right fitting. There is a special hose fitting available from Geno's Garage that is perfect for this purpose.

2) The air bubbles won't hurt anything. They will elastically transmit the fuel pressure to the guage, so they aren't goofing up your readings. Disconnecting the gauge to let off the pressure might help to zero the gauge.

If you get FP readings that are fishy, there's a VERY high chance of probability that the isolator has failed or is about to. With isolators, failure is a question of WHEN not IF.

If the system is fine as is, then leave it. But if you have problems, the first thing to do is ditch the isolator and run fuel right to the gauge. You'll also want to plumb in a small needle valve to the gauge so that you can 1) shut off fuel in the freak chance that you have a leak, and 2) dampen the pulses from the VP44 that seem to cause gauge noise and/or failure.

Finally, I can't recommend highly enough Scotty's Smart Fuel system. It's inexpensive, VERY high quality, and fixes the problems with the OEM setup while keeping what's good about it. See for yourself: http://www.scottyairsystems.com/2nd%...art%20Fuel.htm

Justin

rockjeep73

thanks for the information.

I'm sure that the isolator and gauge are working fine, they are also brand new. Also, the gauge only reads 2psi when the truck is off after I have been driving for at least 30 minutes, so I think it may have something to do with the underhood temperature, because once it cools down (overnight) it drops back to zero and acts normal. So not a big deal.

Oh yeah, the lift pump is pretty much gone, at idle I only get 5psi and any amount of throttle it drops to 0psi, it hurts to drive it like this but im forced to until the weekend, and as far as I know the truck may have been like this for several thousand miles.

And as far as the scotty fuel system goes, I already have a FASS unit with all the hose and fittings ready to be installed, and as far as I know it completly bypasses the stock filter, so that system wouldnt be necessary.

Thanks Again