C250 - can't prime fuel pump

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grumpynorthener

New Member
Joined
Nov 20, 2019
Messages
6
Location
Sheffield
Car
C220
Hi All

I'll keep as brief as possible. 2015 C250 OM651 engine. 7 speed auto.

Timing chain rattle on start up. Inspection showed plastic guide had broken. Engine removed. Chain, tensioner and guides replaced. All refitted with no problems.

Engine cranks but will not fire. Fuel filter primed by bleeding from plastic valve on end of 30cm hose from filter top.

Scanner shows 4 bar pressure which i assume is lift pump.

Have tried cracking off injector pipe between rail and injector but no joy.

High pressure pump is gear driven, so must be working when engine is cranked, so am i right in assuming an air lock in pump?

How do i bleed the high pressure pump?
 
My guess is air lock in injectors (common for piezos). PITA to solve when all injectors have been removed, laid on wherever, letting air in.

Edit: I just read again, you mean rail pressure is 4 bar? Then you must have problems with fuel quantity or rail pressure valve. HP pump are not usually failing on these. Gear driven pump do have instuction for 'timing' too (just for better pressure behavior), and it should not affect on building the pressure.
 
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