1987 300 tdt won't start

This is my friends car, He got stranded in Tenn. so I hauled him and his vehicle back home. He had had problems with the thing not wanting to start but if he tried it several times finally it would. It seems to not crank
real fast even with the battery fully charged. This is a diesel. It seems that either it is not getting air or fuel. I wonder is the device that shuts the engine down when you turn off the key is not allowing it to start. We took off the air filter cover and tried a shot of starter fluid. He cranked the engine but never got a hit. I know on my ford diesel truck there is a fuel shut off valve that cuts off the fuel supply to kill the engine. I know nothing about mercedes diesels. Any ideas? Thanks Joe
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Replace the glow plugs and it will start. Pkmaven

shuts
cranked
know
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On my diesal truck I test the glow plugs with a continuity tester from the glow plug tip to ground. Do these test the same way? Thanks Joe

start
seems
We
a
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Turned out that it was the clutch on the ac compressor. The locked up compressor/clutch was causing the slow cranking. Thanks Joe

start
seems
We
a
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yes, there is a vacuum powered shut down device on the aft end of the injection pump; a brown vacuum line is connected to it. However, the engine usually fails to stop when the shut down's bellows are broken and can't pull the fuel rack to OFF. I don't believe that's the problem.
These engines use glow plugs to preheat their prechambers so the engine will fire. There's a glow plug relay on the left fender. It has a plastic cover that slides UP exposing an 80 amp fusible link or fuse. It's probably broken, killing the glow plug system. One can jump this link temporarily with a stout copper wire - but only temporarily. The 80 amp link is available from the dealer and others for about $1. Also buy a spare.
The other possibility is no fuel due to a clogged pick-up sock inside the tank, clogged filters. There are two, the small clear plastic one down at the hand primer pump and the main spin on filter aft of the power steering pump. You can check fuel delivery by cracking open a high pressure line to an injector - it should leak when the engine is cranked. Tighten it carefully - not too much or the line gets crushed. An air leak into the fuel system is also a possibility, especially if someone recently worked on it. Tighten all the fuel line connections between the tank and the injection pump. Open the fuel cap to ensure there's no vacuum inside the tank due to a clogged tank vent - unlikely, but could happen.
Finally, a warning. M-B diesels use prechambers for (relatively) smoother running; starter fluid can crack the prechambers so don't use it!
Hope this helps you get rolling.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.