EFI 150 fuel problem

[Ken at Darwin]

I have a 2008 EFI 150 MERCURY that will run like a dream all day at above about 1200rpm. At below these revs it will run for a few minutes then stalls and will not start again. If I remove the cover there is a small valve ( looks like a car tyre valve) on the vapour seperator. I press the valve and get a few bubbles and splutters of fuel then a continuous trickle of fuel. The motor starts and runs perfectly again until I operate at low revs again then it starts all over. Have checked and replaced all fuel hoses and the hand pump without success. Can anyone help please. I dont enjoy hanging off the back of my boat , the crocodiles here are far from friendly

 

[fastjeff]

You're getting air into the system. Have to find out where. Its before the fuel pump.

Jeff

 

[Ken at Darwin]

Thanks Jeff
I'll have to keep replacing bits. Was worried it might be the gaskets and diaphram in the fuel pump

 

[faztbullet]

Its not getting air into system......... That's the fuel pressure Schrader valve and it will only have pressure when high pressure fuel pump is running(35-39psi).Could be one of the following: 1) low pressure mechanical pump is weak and not keeping VST filled...2) high pressure pump...3) ECU driver has a problem or 4) fuel pressure regulator is failing

 

[Ken at Darwin]

Thanks for the further input. Ive got something to look for now
One other thing that has developed with this problem is that I cant pump fuel up with the hand pump it just seems to suck air back and forth as I sqeeze and release. I replaced the pump and fuel hoses but no change