I have a fuel pressure guage with an isolator into the inlet of my cp3 pump, I was told to fill the line with rv antifreeze and it would be okay. My question is that after 2-3 week without driving it, I have to refill the antifreeze (by means of just refilling the isolator) to make my guage read correctly. Is this normal or do I have a leaking isolator? If so this is not a good thing for my fuel pump to be seeing.

 

No, it is not normal...

Man, I threw my isolator away, I never could get it right. I just run diesel straight into the cab, been doing it for years with no problems.

 

Thia may be a stupid question, but which side of the isolator are you filling with anti-freeze - the pump side or the gauge side?
I am with madhat. Forget the isolator and run a line directly into the cab. Just make sure that the line operating pressure is considerably higher than what you will be running and also that the line is for diesel.
For safety, (in the extremely small case of a burst line in the cab), at the pump, install a very small orifice. This will limit the amount of fuel that can gush into the cab and will also serve to cut down on any needle pulsations. I have run that setup for years with absolutely zero problems.

 

What I have is that clear spaghetti line that was supplied in the kit. I don't know if that is diesel compatible or not. I hope it is that way, getting the isolator out of the way will be easy. Also with that out of the way, as the lift pump does its thing do you have to bleed the air out of the line or not? Thanks.

 

Just hook it up and roll with it.

 

Thanks for the advise.

 

I wouldn't recommend high pressure fuel lines inside the cab. That's a recipe for disaster. Yes, a lot of people have gotten away with it. But, it's a mechanical device, and will eventually fail. I wouldn't risk it.

Their are no racing sanctioning bodies that would allow that through tech, either.

The isolater is a great idea. But they don't seem to be made well, and fail often.

I would use an electric gauge.

 

High pressure? 15 psi?

 

Would it help matters if I mounted the isolator closer to the cab or is that a waste of time. I will admit I really dont like the idea of diesel in the cab, but I am tired of the isolator. Where is the antifreeze going? If the isolator was leaking you would think I would see diesel in the line. 15 psi is not what I am seeing, more like 8. Please dont tell me my lift pump is going. Well positive pressure is a sure sign of flow.

 

I have an aftermarket pump.

If you are concerned about fuel in the cab, get a gauge with an electronic sender.

 

I get your point, just do it.

 

I used a 40 PSI working pressure metal covered hose from the pump to the hose. Drastic overkill for sure, but it gave me peace of mind. I also have a very, very small orifice at the pump. Agreed, it goes against "the rules" but it eliminated the problematic isolator and in the 6 years it has been installed, has never given any problems. I also carry a plug in the truck so that if the hose ever did leak I could quickly remove it from the pump and plug the fitting.

 

Finally, can you by chance so me pics and what exactly you used you parts. I thank you all for the input.

 

No pics as everything is installed and sort of buried, but I will explain how I did mine.

The AirDog system I installed on my truck uses a steel elbow where it connects to the IP. I drilled and tapped that elbow to accept a nipple to connect to the gauge. Before installing the nipple I made my own orifice by using a piece of aluminum rod that just slid inside the nipple. Don't laugh, but an aluminum nail for a gutter was a nice fit. I cut a piece of that nail to about a 3/8" length and drilled a 1/16" hole more or less in the middle. Then I found a steel punch that was loose fit inside the nipple and clamped that in a vise and positioned the nipple with a the piece of aluminum approximately centered inside it and pounded on the opposite end with another punch to swell the aluminum to lock it inside the nipple. Every few bangs with the hammer would take a look thru the center of the nipple to see how small the 1/16" hole had shrank. I quit when I could barely seen any light shining thru. That is now my orifice. This very small orifice serves to damped any pulsations from the LP and also serves as a sort of safety valve in case the line to the gauge leaks or the gauge itself leaks. Not much fuel, even under pressure will get thru a hole that light barely shines thru.

Hope this explanation helps you.