i put in a dipricol fp gauge about 6 months ago, worked great util 2 days ago. i went and started the truck in the morning to go to work and the pressure was a little low, im due for a new filter soon so i didnt really pay attention to it. but i went about a mile down the road and my pressure was slowly going down. and now it wont go above like 5-7 psi, but when driving it doesnt move. i dont think the gauge is reading right because the truck is driving the same. it did get cold the night b4 it started acting up, could this have anything to do with it? or is there somthing else wrong?

 

Since you said you need a new filter, I would change it, and tehn see what happens.

 

you have air in the line between the isolator and gauge. it will cause the isolator to max out and make the gauge read lower. It took me several tries to get mine bled so it won't do it any more

 

pull the cab side line on the isolator. fill with anti-freeze until the isolator is topped off. re-install the line and fire up. the line from the isolator to the gauge does not have to be filled, just the isolator. Mine did this when I put my GDP392 kit on.