adidasman23

i am doing this for a friend so i haven't read any of the 3gen thread because i have a 2nd gen. but anyways, he has an 06 dually and we put a isspro macanical gauge on his truck and it is reading 9psi at idle and it will go down to 1psi. i think the gauge is wrong because of the diafram. what should the pressure be and where would you put the tap into the line be. we put it on the line going into the fuel pump. do you think the gauge is the problem or do you think it is his truck. i have another gauge for him but he is out of state and i can't change it. he is just calling me and telling me there afraid of his truck blowning up.

35" 05'

mine is the same thing. 9 psi and can drop quick

adidasman23

does yours drop to 1psi. is it the gauge or the truck

35" 05'

i believe its the truck. gauges are brand new. i think the dealership should put a bigger pump on even for stock......wait for someone else to jump in and say something

adidasman23

ya well i have never put an machanical gauge on a truck. i didn't like it. he bought it without telling me

badcompany

I was thinking about getting one of there gauges but do I have to run a fuel line into the cab or is that what the fuel pressure isolator is for? Would like to buy one them but not to fond about having fuel in cab. Could someone tell what to buy so I could stay way from that. Thanks

FiverBob

I run about 9 when idling. I have never seen 1, even when floored towing 16,000lbs up a 9% grade. It would run about 5 doing that. Obviously, the condition of the fuel filter affects the loaded pressure quite dramatically.

adidasman23

no you don't run fuel into the cab. on the other side of the diaphram you run anti freese. well that is what i was told

adidasman23

well i have another friend that doesn't see below 5psi on his 06 MC. he also has the autometer gauge not isspro.

yelloz28

I was seeing 3-4 at idle and could draw to 0

badcompany

ok thanks for the help

P.J

I run fuel into the cab, second truck I have done this way. I think you will find a majority of us prefer it this way.

Isolators are a inaccurate reading waiting to happen.

Thread started by me a year and a half ago, before I installed the gauges in my old truck:
https://www.dieseltruckresource.com/...echanical+fuel

Here is a poll, I think if someone started another one for JUST the guys that have either an isolator or fuel straight to the back of the gauge (in other words, take out ELECTRICAL) you would find that very, very few people have had issues, the ones that did most likely found out it was due to an error during the install (crimped line, loose compression fitting, etc.)
https://www.dieseltruckresource.com/...highlight=Leak

P.J

To answer the OP, I would bet $50.00 it's a faulty isolator.

Mine (same truck) sits at about 8-9 idle and I can't suck it below 6 WOT (stock truck).

badcompany

Would i put the gauge before the fuel filter houseing or after?

tdm

Mine also idles around 10-11 pounds and will drop to 5 at WOT. I was a little worried about it at first so I talked with my local Dodge tech. He made the comment that the newer trucks don't worry so much about pressure, more about the volume. He stated that 10 is spec and that they can drop down to 2-3 without issues. If below that he said to check FF, if good you have some other issue to find.... like LP.