I'm hoping somebody can help me here...the other day about 7 hours into a 10 hour drive I noticed that my fp gauge was going wild...usually it sits right at 5 psi, shakes a little at idle but nothing major, but man this was a wild shake, at idle the needle was almost bouncing off the 0 and goes to 10, almost in sync with the idle....at higher rpm it gets better, but still sucks to look at...mechanical gauge, no snubber....when I started it the other morning it read normal (5psi) until it warmed up and then it was the same old thing...does this have to do with warmer fuel and the fact I have no snubber? I have a fuel filter with me and a spare(used) lift pump that I could try...

 

Mine does not do that no matter where I have my snubber valve set. But my pump is on its last leg. 3.5 to 4 psi at idle. I have an isolator on mine also.

 

With no snubber or barely cracked needle valve, you're gauge is on its way to the landfill.

 

I guess my big question is why does it give a normal reading on startup and until the engine reaches normal operating temp, does that just have to do with the gauge itself? Its been plumbed in for over a year (banjo pre-filter) and I didnt see it doing it last summer...the movement is so violent I'm worried the gauge might crack or something internal...changed the filter this morning but havent warmed it up enough to get the same thing happening...did verify the manual operation of the lift pump though, also gained a couple psi fuel pressure at rpm....thanx....

 

Yup, still shook like a witch when she got up to operating temp, so I plumbed in a valve, and its a little touchy but seems to keep the reading steady, the only thing is its not very sensitive, at wot it doesnt drop much....I still want to know why it shakes like that though..

 

The shake is the pulse of the fuel pump.