my 300d will not start. it does turn over, the glow plugs are good and
the preheat appears to work.
Ive pumped up the fuel pressure(its been sitting a while)and verifiesd
there is fuel getting thru the filters.
it acts like the engine stop portion of the fuel manifold has stuck in
the stop position.
I have been unable to find any drawings diagrams of this system. I dont
want to blindly take this thing apart. I do have a haynes manual but it
doesnt tell me much about the injector manifold or stop circuit.
It only has about 150k on it. I have replaced most of the glow plugs,
and verified continuity thru all 5 plugs.
i was told a couple years ago by a merceds only shop that it has a week
cylinder, but has been starting fine as long as the glow plugs were
The engine stop device is a vacuum powered bellows in the aft part of
the injection pump. This little bellows wears out and gets oil logged.
Suggest you look at the aft end of the injection pump for a brown??
plastic vacuum line attached to a silver dollar size & shape device and
detach the vacuum line therefrom. If there's any lube oil in the vacuum
line the "shut down device" (bellows) is holed and must be replaced. You
can temporarily plug that vacuum line and use the car. But one must then
stop the engine manually by pressing the STOP lever on the engine's
If you want to replace the shut down device yourself be forewarned that
its not hard to do but IS tricky in that one needs to hook the end of
the bellows onto the end of the fuel rack (which it pulls to OFF when
one turns the key to OFF.)
Hope this helps you get underway.
Here's how the stop thingy works: when vacuum is applied to it
it pulls a rubber diaphragm inside which causes a lever to pull
a rod inside the injection pump which cuts the flow of fuel.
When the thingy fails it gets a hole in the rubber and all the suck
in the world won't make that lever move. That is, when it fails
you con't turn the engine off.
It's really really really unlikely it's failed stuck in the off position
which would require vacuum to be asserted, well, pretty much forever.
I take it the car has sat awhile? Not uncommon and you have two choices:
1) crank and crank and crank forever till you fluch the gum and crud out or
pull it to 35 mph and shove it into drive and it'll start. The latter
is what I've seen usually dont and I've never seen one that failed to
start this way.
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.