OM617 not starting - PeachParts Mercedes-Benz Forum

DieselPaul · #1 05-26-2012, 10:22 AM

I picked up a W116 1980 300SD yesterday as a potential beater / potential parts car. Regardless of its function the price was right. At the very least I would like get it running so I know I have a good motor that I can hold onto for a future swap, or sell it as part of a part out.

I took all 5 injectors out and put a little oil down into the cylinders as I messed with other things, the car ran when parked, 8 years ago or so. So I wanted to get a little oil down in there.

We put the new dealer battery from my 190D in the car. The dome lights came on, the blower motor came right on, etc. However when you turn the key to glow the light flashes quickly, and then when you turn to start, nothing happens.

So I ran a jumper wire down to the starter, and it will crank over really strongly, but it won't start.

I cracked the injector lines, and I get some bubbling but no big quantities of fuel.

When I pushed the primer pump a few times, I actually saw a little diesel leak out of the primer on the down stroke.

Fuel filters look reallllllly old and the main filter is rusty on the outside so I'll throw a new fuel filter at it.

I should probably blow some air though the feed line from the tank to make sure I've got flow.

So here is my question:

Is there a main fuse / relay for the starting system on the W116 with an OM617 that I should look into?

Any other suggestions diagnosing the fuel system?

Diesel911 · #2 05-26-2012, 10:51 AM

If you do not know already to the Diesel Giant Site and see how to check the Glow Plugs.

If it has an Automatic Transmission the Neutral Safety Switch could be shot. That would keep the Starter from Cranking; and worn shifter bushings can cause the same issue.

Try starting in Neutral or giggling the Shifter around. If the Engine trys to crank after that you have narrowed down the problem area.

On my 84 300d the Neutral Safety Switch Wires colors are Purple (Violet?); see if there is a Connector you can disconnect and jumper the Terminals.
Also on my year and model the Neutral Safety Switch controls the Back Up Lights so you are going to see more than 2 Wires attached to the Switch.

DieselPaul · #3 05-27-2012, 12:36 PM

Well I found the glow plug relay, fuse was good, power on both sides, then I slid back the sheathing on the wire and found this...

Some critters got into the wire, 2 wires had the coating chewed off and one wire was chewed in half. So I insulted the 2, and soldered the other back together.

Success

However it still won't start, and even when I use my jumper wire on the starter it still isn't getting fuel, I picked up a pair of fuel filters so that is my next job and I was going to blow some air through the line to the tank.

However I also found these,

On the firewall

Near the transmission dipstick

And then this one, which I can't figure out where it used to go

It runs up the fender under the fuse box and into the cabin I think, but then I lose it.

I'm very unfamiliar with 617s and 116s so I don't really know where these should go, if they don't affect the car running I probably am not interested in repairing them at this point.

And like I mentioned earlier the primer pump leaks when you pump it, it looks like the primer plunger has a 6 pointed bottom and it could come off, is that true? And is there an O-ring or something in there I can replace?

Stretch · #4 05-27-2012, 12:45 PM

If the primer pump is leaking there's a good chance there's air getting in there. Either replace the primer pump or if you are smart bleed the system with the dodgy primer pump fitted but locked in the closed position via the return fuel line - you might get away with that.

Small fuel filter is the primary filter which is connected to the supply line; large screw on filter is the secondary filter which is closest to the return fuel line.

DieselPaul · #5 05-27-2012, 02:59 PM

I went ahead and ordered a new style primer pump off of ebay, $14.50 shipped for a bosch one. I'll see if I can get it going without, but the car behaves like air is getting into the system because I can get a little bit of fuel to bubble out of the hard lines.