Fuel pressure drops to zero as soon as motor is shut off.

[Kamaka Z]

just installed my new Pallnet fuel rail with stock injectors. I have a pressure gauge installed right after the filter. before the new fuel rail when i shut down the engine the pressure would stay up for quite a while. Now when i shut  down the engine the pressure drops to zero within seconds. I used a 280zx fuel pressure regulator. Is this normal or is there a leak somewhere?

Thanks for the help

Randy.

[NewZed]

Not normal for a factory FPR.  Did you switch FPR's or use the same one?

 

It would only take a small piece of rubber or teflon tape to hold the seat open in the FPR.  Some old FPR's will occasionally lose pressure but hold most of the time or vice-versa.  It looks like maybe you only checked once before and once after.  You don't give much detail.

 

Regardless, it will only affect starting the engine quickly.

[Kamaka Z]

I replaced the oem 280Z FPR with a new oem 280ZX FPR. I just dont know if the new FPR is not holding pressure or if its leaking down somewhere else.

[NewZed]

You could block the return line and test that way, or block a port on the 76 FPR and put it back on.  Or you could just use it for a while and see if the new FPR settles in.  Might have some surface rust inside, if "new" means "new old stock".

 

I'd drive it for a while and see what happens.  Won't hurt anything.  Might be aggravating.  If it's leaking at an injector you'll probably notice it's very rich on starting.  Might even foul a plug.

[Kamaka Z]

 thanks for the help I'll try you suggestions. The new FPR is a new aftermarket oem style.

Edited November 26, 2015 by Kamaka Z

[NewZed]

Never mind, mistake. Erased previous comment.

 

 

Might just be poor quality on the aftermarket FPR.  It might still wear in though, with time.

 

Probably best though, If you confirm that it's the 280ZX FPR, to take it back and exchange it.  They're not supposed to leak down.

Edited November 26, 2015 by NewZed