Fuel dumps to bottom cyl Merc 250 EFI

[Jon McC]

I have a 2000 250 EFI Merc . I pump the bulb and turn key , fuel builds to 40 psi . pump shuts off after 20 seconds and pressurs holds till I turn off key . Fuel pressure drops and large amount of fuel ends up in bottom cylinder . I changed diaphram pump and bottom injector looks ok . If pressure reg is bad would it dump into airbox ? I changed electric pump last year , and do not understand why removing power would cause a fuel pressure drop . Could a check valve in pump be the cause ? Any help will be appreicated , Thanks

 

[rodbolt]

Re: Fuel dumps to bottom cyl Merc 250 EFI

the regulator vents and uses a vacum signal from the intake.
remove the airbox and cycle the keyswitch while observing.
wear eye protection as 40 PSI fuel leaks can get nasty.
sounds like either a leaking injector or regulator.