lwcmattlifter

Hey guys, I have a quick question. I installed a set of Isspro gauges (pyro, boost and fuel pressure) on my 01 2500 this weekend. Everything works fine except the FP gauge, I think. I have 11-12 psi at idle and it drops to 6-8 under heavy acceleration. When I turn engine off the gauge stays at 10 psi. Is this normal? I was thinking it should go back to 0, right? BTW it's a mechanical gauge.

Matt

MKELLY

Yes, it should return to 0 psi, I've got a mechanical Isspro also, but have never seen that condition.

Shovelhead

If you're using a needle valve as a snubber, turn it about another 1/8 turn open, or until you see the pressure drop fairly quickly when you shut the engine off.

lwcmattlifter

I'm not using a needle valve. I have a braided fuel lind connected to a banjo bolt replacing the schrader valve on the IP. The other side of the hose goes to an isolator. Should I be using a needle valve?

JD farmboy

Yeah, if you don't the pulses from the pump will eventually damage your mechanical guage.

lwcmattlifter

I thought the isolator was supposed to stop the pulsing. Do I need any special needle valve and which side of the isolator should it be on?

Shovelhead

The isolator only provides a diaphram to keep diesel fuel from coming up the line to the gauge.
The "inside" section of the line is usually filled with anti-freeze.

The isolator shouldn't cause the gauge to "hang".
If you disconnect the line at the source, does the pressure reading drop?

A needle valve is usually installed on the engine side of the fuel line near the source.
This is the setup on my '99.
https://www.dieseltruckresource.com/...ure_Hookup.jpg

lwcmattlifter

If i crack the line at the source, pressure drops to 0.

Shovelhead

Most folks use a banjo bolt that's drilled and tapped for 1/8 NPT thread to replace the banjo at the feed line into the IP.

Maybe the port you're using has an internal valve that holds pressure.
I know some have tried using a line attached directly to the schrader valve and forgot to remove the 'core'.

lwcmattlifter

I replaced the schrader valve with a banjo bolt from Diesel Manor.

JD farmboy

check out this thread

https://www.dieseltruckresource.com/...pressure+stays

lwcmattlifter

Thanks for the link JD. I really hope this isolator isn't broken because it barely has 15 miles on it. I'm going to stop by NAPA or Grainger tomorrow for a needle valve, hopefully that will help.