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engine turns over but wont start

iansjoey

New Member
Joined
May 29, 2025
Messages
4
Location
northwales
Car
mercedes sprinter w906
help needed please engine turns over but wont start fault code p0087 fuel rail pressure too low
so pressure tested the tank pump 7 bar more than enough
so fitted a new rail pressure sensor
so fitted a new high pressure pump
any suggestions guys im drawing blanks now
engine is the w906
 
w906 can have 4 different engines... 3 diesel and one gasoline (and perhaps one natural gas). As above measure injector leak.
 
Tested the injectors?
Hi no as unsure how too do it on this type of engine easy on ford these seem much more complex
Do you have any advice please or a link too a how too vid
Engine won’t start I’m in belief that a bleed off test the engine is required too be running all be it poorly ?
 
w906 can have 4 different engines... 3 diesel and one gasoline (and perhaps one natural gas). As above measure injector leak.
Hi no as unsure how too do it on this type of engine easy on ford these seem much more complex
Do you have any advice please or a link too a how too vid
Engine won’t start I’m in belief that a bleed off test the engine is required too be running all be it poorly ?
 
Yep... engine needs to be running to check bleed off.
How's the battery?....these engines need to spin at a certain minimum speed before the injectors will fire.....too tired to Google it but iirc it's about 200 rpm.
 
No it does not. Cranking 1 minute is enough. Bad ileaky injector is revealed even then. Youtuuub full of videos (in case it is diesel...)
 
I've seen that....but in the real world it needs to run to get enough volume in the tubes for meaningful data....unless one is REALLY bad of course. I have assumed derv from post one
For a derv to run, even badly it only needs a little fuel as it will always have more than enough air. So as said, bad injectors, battery not spinning over fast enough. The thing that would make me think it's not exccesive leak back would be, from how the OP described it, the sudden onset of the problem. When I've had this, Jeep and Alfa, when it was leak off, it appeared over time...with the cranking times getting longer and longer until one day is did not start due to minimum rail pressure not being reached. Also cranking over a direct injection derv for long periods can damage the high pressure pump....the only thing cooling and lubing it is the derv running through it.
 
Hi no as unsure how too do it on this type of engine easy on ford these seem much more complex
Do you have any advice please or a link too a how too vid
Engine won’t start I’m in belief that a bleed off test the engine is required too be running all be it poorly ?
You dont need to have it running in this case, if it is an injector causing the issue it will be fairly obvious which one it is. Disconnect the leak off rail from all injectors and lightly clamp the line leading away from them to stop drawing in too much air to the system, connect your test tubes up to each injector and wind the engine over on the starter for 10 secs. If one injector fills the tube much quicker than the rest replace it.
 
Thank you for guidance not too complex then will give this a go and see where we’re at
An update on this thread as I progress along my problem till resolved cheers fellow mb owners
Oh and for ref it is a diesel it’s my brothers van just trying my best too help him out
 

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