So replaced the hpfp head and now getting the desired fuel rail pressure but still not starting, sounds like its almost trying.
What would be the next thing to do, leak off test now theres good pressure in the rail?
Any ideas please.
Yh that valve on the pumps high pressure outlet.
A leak test did not show any leaking injectors, at least not in that way. The cylinders do not appear to be locking up due to filling with fuel as it still quite happily cranks but not faster than you would expect i.e snapped chaindrive
Cant...
Yes.
4B90 - Low fuel rail pressure on start
Getting 4/5bar pre-supply
QCV around 33%
PCV around 35%
Rail pressure starts at 10bar, only rises to 15bar now but it was at one point building up to 180bar and trying to fire.
So to test that would I need to put a meter across the ecm power supply pin and ecm ground pin to monitor the voltage whilst cranking?
A good ecm and ground to it will maintain 12v whilst cranking, a suspect ecm unit or ground would be indicated by a substantial drop in voltage? What would be...
Just had a new battery fitted though cant remember if that was before or after taking these readings.
Also its possible the battery had drained from cranking.
Thankyou for the quuck response.
Its a BMW with a no start.
Pre-supply pressure is 73psi/5bar on a gauge t'd in which drops slightly to around 4bar on cranking.
QCV is normally open, direct 12v applied and it closes. Reads around 2.5ohms. 2 wire fed, with 12v and 3 5v whilst disconnected, key...
Firstly, apologies if this is in the wrong category.
Very glad I stumbled across this forum, very knowledgeable individuals here who hopefully can assist.
My issue is low fuel rail pressure and highly suspect the pump to be at fault.
My understanding of how the fuel high pressure supply from...
