well I've had the zxt+ in for a few weeks now maybe 100km on it and I don't have a fuel pressure quage so I set up my temporary quage to day and guess what?....I got problems!

@ first start, 15 PSI .....for about 15-20 seconds then, 1-2 PSI steady. and it stays @ 1-2 PSI.

what the heck? so I got out my long jumper for the LP and run the LP with the truck off.
I get the same thing. and when the fuel pressure drops the LP changes pitch like its sucking air I haven't dug around very much but I don't think I have any visible leaks any where. The LP is a carter I replaced about 30,000km ago and is still located on the block.

FP drops rapidly from 15 psi to 1 psi in about a second, with or without the engine running.

Is there anything i should check?? I assume there must be air getting in but ??

 

my buddy had the same problem, he only had 4,000 miles on a new pump and it was the pump that was bad again.

 

well it was the pump! I thought it was cavitating from air getting in somwhere, but I put my spare pump in and I get 12 psi @ idle and 9 psi WOT......

Time to get a Fuel pressure guage I guess, its prolly been out to lunch for a while, I'm thinking its a good thing I started using 2 stroke this year!!!

 

I'll bet the bypass valve in the old LP is shot. Shake the pump in your hand and see if it sounds like an empty paint can with the mixing ball rattling around.