I'm running the in tank fuel pump and the return hose is bouncing around at 6ish psi. Any ideas? I still have the stock lines to and from the tank from when it was fuel injected. Is the return line too small? Has anyone else run into this?

 

you mean you have the gauge on the feed to the carb and its bouncing? return pressure doesnt mean anything unless you have a problem.

 

I just ran into this on my 91 Vert 305 TBI to carb swap - 4309 using stock feed and return lines - let it start bouncing good again - quickly run around to the gas filler and take your gas cap completely off - run around to the gage again and see if it stops . I had some sort of weird pressurization after heating up thing happening that was the cause of mine . Mine was bouncing crazy in spells from say 6-40 , 6-40 . 6-40 psi like a windshield wiper - I am assuming this is what yours is doing .

 

Its not the gauge (although that does a bit too), its the actual fuel hose itself coming off the bottom of the FPR.

 

So let me understand exactly what you are saying - you have an inline gage mounted on the return line going back to the tank ?

 

No, forget the gauge, it has nothing to do with the gauge. The gauge itself is mounted right to the FPR. The rubber hose that goes between the regulator and the return line back to the tank is bouncing around.

 

Wow! That's weird as all get-out. I've used quite a few of them myself and never see that!

Take off the gas cap, remove the return line from the bottom of the regulator and see if you can blow through it. Should take a little effort, but you should be able to do it. (Your lungs can generate about 1/4 PSI of pressure, unless you are a Peruvian mountain climber, which should be more than enough to pass air through an unobstructed line)

 

I'll give it a shot, see what happens.

 

I did that to mine with an air hose and line and was surprised some gas droplets actually blew out of the gas tank filler neck even though that little metal flapper trap door is in there ...mine is sprung a little and is always open by like 25% .....so there should be plenty of unobstructed flow in that return line ...I still think you have some sort of weird suction or vacuum thing happening ......take the gas cap off and see if the line stops bouncing around just for grins next time its happening.