XSeries-forum

Been having probs lately with starting. Have changed crank sensor, HP fuel sensor, battery and inline fuel pump. Not much difference to be honest. Starts fine when cold but once heats up problem occurs. Shows fault "rail pressure on start up" on diagnostics. New in line pump kicking out 3.8 bar. Car will always start after connection of external battery pack.

Not sure where to go next aprt from a trade in!!  ; :hmmm:

Welcome aboard........sorry it's not such a good entry message. 

Hopefully one of the knowledgable pre facelift owners will be along with some ideas.

Can you tell us which year, any options, and mods etc fitted?  Assuming it's a pre-facelift 5-speed auto diesel from you description.

Richard

[quote="kennyfin73"]
Been having probs lately with starting. Have changed crank sensor, HP fuel sensor, battery and inline fuel pump. Not much difference to be honest. Starts fine when cold but once heats up problem occurs. Shows fault "rail pressure on start up" on diagnostics. New in line pump kicking out 3.8 bar. Car will always start after connection of external battery pack.

Not sure where to go next aprt from a trade in!!  ; :hmmm:
[/quote]
I would put a amp/ clamp meter on to monitor the starter motor . Sounds like it may be pulling too many amps when warm.
There are certain Italian starters fitted ( someone will prompt us with the correct name ) this could be pulling the voltage down in the battery, so throwing up odd fault codes. But with the additional battery power of the booster it is keeping the volts up so starting ok. ( Minnelli or something !!! ) worth putting a meter on to test, someone will know what the starter should pull ?

Magneti Marelli are the beasties.  Get a Bosch one.

Should pull around 700A or so when cold, and not exceed 830A as that is the battery rating.  Faulty ones can exceed 900A CCA - which drops the battery volts so the crank goes slow.

R

Thanks for the replies. Looking like its the HP pump. Does anybody know if a new one needs coding in from BMW or is it a straight swap out.
Thanks