W124 300D Non Start-Fuel System

[gmcity]

My 91 W124 300D won't start, and a mechanic who tested it came up with this diagnosis. The starter turns it rapidly. The engine itself is in very good condition, plenty of compression, clean oil and coolant. All the glowplugs work. Fuel is being sent correctly up to the large injector pump, and then at the other end, the injector pipes are only dribbling a small amount of fuel. This indicates a failed injector pump, apparently. Could you tell me if this is right, or if there are other less costly solutions? What about the secondary pump on the side of the injector pump? I have located a reasonably priced injector pump, but the Haynes manual says I need a special locking tool to keep the timing in the pump correct. What steps do I need to take? Thanks.

 

[Bolide]

AFAIK there's only one pump on an early W124 diesel - the injection pump. If the pump has a _good_ fuel feed but the injectors are not cracking open then I'd suspect the pump

You just need to make sure the new pump is timed the same as the old one. Whatever method you use for this is fine. Mercedes produce a special tool but I'd expect any competent diesel expert to be able to do it without

Nick Froome
www.w124.co.uk

 

[g-class merv]

Suspect your car has a vac stop,
Is it working properly?

 

[gmcity]

Vac Stop

Could you please remind me where I might find the "Vac Stop"? I have the radiator off at the moment (the fan's off next),and the air cleaner and tubes to the inlet manifold - so I can see a lot of the Pump and ancillaries. If I can test the Vac Stop. and any other accessible areas, while things are at this stage, that would be handy. If I have to go as far as removing and replacing the fuel/injection pump, are there good workarounds when it comes to keeping the Sprocket and the timing device in place in the Timing Chain casing, so it doesn't disengage from the chain? Thanks.