When installing the fuel pressure guage with an isolator, is it reccomended to use a needle valve? If so, where is the best place to install it? Just before the isolator or ri9ght at the point that it is T'd into the fuel line?

Thanx in advance

atch

 

I'm thinking that the isolator does the same thing as the needle valve. One is suppose to keep fuel from getting to the cab and the other to turn it off if it does.

 

In this case the needle valve works as a snubber. A snubber stops the hard pulsations made by the injection pump. These pulsations actualy vibrate the isolator diafram which in turn makes the gauge needle not work smoothly, shortening the life of your gauge. You can mount it in either place. Most prefer where you Tee into your fuel ilne so you can stop flow to your gauge if you ever need to replace/fix it.