Hi all.
Can someone explain how the vacuum fuel rail sensor works. I have just had a look at mine with a cold engine I can suck on the pipe from the inlet manifold to the sensor and can’t get a vacuum. This might be correct and as the fuel rail heats up the sensor closes to allow vacuum to the fuel pressure regulator. I ask because mine is a little difficult to start when hot and runs a little rough but only for a few minutes. Cold stating is perfect with cold tick over about 900rpm dropping to 650 when warmed up.
cheers Rob.

 

My understanding.

Cold engine.
Vac passes to the FPR as normal, and that allows vac regulation of the fuel pressure. 35ish PSI.

HOT engine, as in a heat soak shutdown.
That sensor closes the vac supply, SO, the FPR defaults to the NO VAC setting, 41psi I think, and that is meant to allow easier HOT starting.

None of mine worked. I removed them, plumbed the vac hose Inlet spigot to the FPR.

HOT starts are fine.

Biggest HOT start issue is grubby contacts at the EFI Resistor Pack plug/socket, RHF corner of the engine bay. Cleaning them WELL, has ceased HOT start issues on 8 down here that I am involved with.

Our summers are HOT by most places, and engine bays get HOT. Fuel boils in the rail. Injectors cannot inject vapor, only liquid.

Also, a couple ON-OFF-ON of the ignition switch very quickly flushes the hot fuel back to the tank.

 

Cheers Grant you are a star. I have checked my valve and it doesn’t work so will do as you say and put a line direct from the manifold to the FPR. I will also have a look at the pack plug and give it spray with contact cleaner.
cheers again. Rob.

 

Rob,

Always remember, less stuff more speed. Does not always sit well with some, but works for me.

That plug pack is best cleaned with Lemon Juice (the real stuff), then rinsed off with WD40 or similar before replugging.

About a 3 beer job, bit awkward to access the mounting screws.