90 350sdl not starting after new glow plug install

[steel]

I've got a 90 350sdl that never had a problem starting cold or warm. I did a continuity ohm test and saw had one high reading so decided to go ahead and have all the glow plugs changed out.

Now the glow plug dash light doesn't light up (it used to) and it is not starting.

I've got 12v to the relay. 12v on the pins coming out of the relay when relay is activated. Engine is turning over strongly but not starting.

What should I check out next?

[compu_85]

What else did you remove when you replaced the glow plugs? If you hook up a test light to one of the glow plugs does it come on when you turn on the key? Can you hear the glow plug relay click?

-J

[MercFan]

There is a large metal strip fuse across the terminals that control the glow plugs. On my 300D it was on the DS fender. Follow the wires and check that fuse.

[steel]

Originally Posted by compu_85

What else did you remove when you replaced the glow plugs? If you hook up a test light to one of the glow plugs does it come on when you turn on the key? Can you hear the glow plug relay click?

-J

Had to remove the manifold to get to the glow plugs.

Not getting a light at the glow plugs but relay clicks on/off. Getting voltage on the pins that go to the glow plug wires.

If there is a short somewhere in the glow plug wires would that prevent the car from firing? It's turning over fine but cylinders not firing.

[steel]

Originally Posted by MercFan

There is a large metal strip fuse across the terminals that control the glow plugs. On my 300D it was on the DS fender. Follow the wires and check that fuse.

This model relay doesn't have that bar fuse on top. But am getting voltage on the pins that go to the glow plug wires.

[compu_85]

Ok. If it's warm out and your motor is in good shape it will start (eventually) without glow plugs.

As noted the 350 doesn't have a fuse on the GP relay, it has a self-resetting circuit breaker.

So you removed the intake. Did you block off the ports with anything when you did that? Is the stop lever free? If your vacuum has bled down it will go to the vertical position. If it's horizontal the engine will not start.

Watch my video here, you'll see the stop lever move up when I turn the key on : Mercedes 350 SDL Diesel S-Class Cold start - YouTube

I once bent the stop lever slightly while working in that area and it got stuck on one of the delivery valves preventing starting.

-J

[steel]

Well it turned out to be a short in one of the glow plug wires. It was making contact with the block. Weird that it would not start even without the glow plugs. Once I fixed the short it roared to life.

Funny now the glow plug light only stays on for about 5-6 seconds. It used to stay on for ~ 30 secs. Did I mess up the relay or is there another short somewhere?

[compu_85]

5-6 sec is what it should do. You probably jiggled the temp sensor wiring and got it working properly again (the sensor on the head near the GPs is for the temp gauge and the GP relay).

-J