I had put in an ISSPRO Fuel pressure mechanical gauge with isolator a few days ago. This is routed from the VP with steel braided line to the isolator mounted on the firewall (no rubber bushings on the isolator mount, I was told that if it was firewall mounted the vibrations would not effect it) and then from the isolator to the gauge is the tube provided with the DieselManor kit in which we put -84 Deg antifreeze (straight, not mixed with water).

The truck is running a FASS 150/95 GPH unit with a 95 GPH pump mounted on the framerail in front of the driver's side rear wheel as per the fass instructions. We used a banjo fitting right off the VP which is where we tapped the fuel pressure. When we put the antifreeze in the tube for the gauge we first filled the isolator diaphragm as much as we could then we filled the tube before putting one end into the isolator connector ferrule and the other end to the gauge and we used Teflon tape on each of the fittings to the isolator. We wanted to try our best to make sure there was no air in the system or any leaks...how much do air bubbles even slight ones, if any, effect the reading?

I'm seeing 13.5psi at idle on the gauge, I can get it as low as 11 but this has only been unloaded driving at full throttle...most of the time around town or highway it'll be right around b/w 12 and 13. I thought with this setup I'd be seeing more like 17 or so at idle and nothing lower than 15 psi at full throttle. My numbers are lower than what I thought...why do you think this is the case? I'd like for the Fuel Pressure to be where others are seeing, right in the 17 -15 range (or higher)...from other folks on the forums

Please let me know what you think..or if there is something I'm not getting or have done not as well as could have been...thanks

 

i used the same kit in my truck..gauge/isolater from diesel manor, and you installed yours just like i did and so far mine has been great with no problems.... been a little over 6 months now, i have checked mine with a good mechanical guage and it reads exactly the same, so im not sure whats going on with yours unless its some with the fass system isnt right?? have you changed your fuel filter recently? that can make a big difference...

 

Are you sure you got all of the air out of the line?
That may make a difference in your readings.
I have a FASS 150/150 running the same gauge.
I see a constant 15 psi.
it will drop to 13.5 psi at WOT.
11 psi at WOT shouldn't be an issue.
I think the stock lift pump runs 11 psi at idle.

 

mx684...The stock Fuel filter and housing has been removed...now there's the FASS unit in place which runs between the tank and the VP...the FASS was put in the same time as the gauge and it included a new fuel filter and air seperator as part of the kit with the pump...all this was done this month, so I don't know if replacing the fuel filter so soon will really change anything...any thoughts?

KenC...how do you check and make sure you have abolutely no air in the line (which line?)? Are you talking about the fuel line from the FASS to the VP (in this case we bumped the starter a couple of times to prime the system)...or the gauge line from the isolator to the gauge (in which case we filled with antifreeze as best we could including the isolator diaphragm and the tube running to the gauge)...

do you think a 150 gph pump would read higher at the VP with my setup than my 95 gph pump? Or should they be the same or right around the same assuming both setups went Tank to FASS to VP (with all the stock stuff removed)

Anyone running a FASS 150/95 - 1008?? please let me know what you're getting for fuel pressure and how your setup is plumbed, especialy if it's the same as mine I'd be very curious to see what number's you're getting....what do you think I should be seeing from my gauge? thanks for the help

 

Higher pressure's aren't neccessarily a good thing in the VP44 pump. Your pressure is running right about were it should. I had my pressure up to 26psi after rebuilding the fuel system. It was strongly recommended to get it down to 13psi or risk overheating the internals.
My pressure is now regulated to around 13.5psi and stays there to within a few psi. I would leave your pressure right were it sits.
Mike

 

Bypass the isolator and run fuel directly to the guage and see what you get (as a test) this will confirm or eliminate the isolator as the problem.

 

I ran straight 3/8" fuel lines from vp pump to filter then drilled banjo bolts from filter to fuel pump and used 5/16" banjo ends from old fuel lines between filter and stock fuel pump. I get 15 1/2lbs at idel and 12 to 13lbs cruiseing speed and drops to about 10lbs at WOT.

 

I was talking about the line to the gauge.
You need to make sure the fuel to the isolator has no air in it. The system may do it on its own.
I had problems getting the 1/8 inch flex line past the isolator to seat at the ferrels. I ended up going to an air-conditioning supply house and bought a full length piece of 1/8 inch copper and ran that from the isolator to the gauge.
I used my vacuum pump to pull the coolant fron the container through to the gauge. Using a separator bottle that came with the vacuum pump, I let the bottle fill with coolant.
I then prefilled the isolator with a syringe and attached the lower line to the isolator while the other side was attached to the bottle back filling the line with coolant.
I then turned the key to start a couple times to see if any air bubbles came out into the bottle.
Attached to the gauge and it works. Can't say I have all air out but I tried

You can contact Diesel Dan if you have any concerns about the FASS.
He is on the board and is the FASS guy.
He would have replied to your post if you used the words FASS in the header.

 

I bet the isolator is messing up your reading. Run fuel straight to the gauge and I bet you will see 15 psi.