I have replaced the glow plugs, reamed the glow plug holes. I get a good voltage drop when I turn on the glow plugs and the glow plug light works as it should, turning off after about 10 seconds. I replaced the 2 fuel filters, bled the system and I'm getting fuel at the injector lines. The starter is turning a bit slow. Could it be that? Is there a way to test starter amp draw? Anything else?

Adjust the valves? Use the block heater?

Starters do get weak and slow with age, so it may be time for a new starter.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Probably a dumb question but how's the compression?

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1986 300SDL, 362K
1984 300D, 138K

Recharge your battery. Sound as though you are just impatient. If it was starting and running well before, it will now. The starter has to turn the engine at a good clip for a reliable cold start. After a filter change, I usually crank with my battery charger in place.

If you did not prefill the secondary fuel filter, it may take many (50 or so) pumps on your primer before it fills both filters and starts. The first start will be rough, then it will smooth out and be reliable thereafter.

Our OM617 fuel systems are self bleeding so don't worry about that. Just crank away, intermittently so you don't fry the starter. It WILL start.

Thanks for your responses. I forgot to mention that I did adjust the valves this week. They were not far off anyway. I did fill the fuel filter before twisting it back on. I also got one of those good Monarch primer pumps from Mercedes source. And like I said, there is fuel at the injector lines when cranking.

As far as the starter, Even with a good charge, it turns. I'm having a hard time determining if it is turning fast enough though. Is the starter a hard job on these? I'm tempted to have it towed in to have the starter replaced. Don't know if I have the patience to do it myself now. But, is there a way to test the function of the starter first?

Might be a good time to replace the block heater. Isn't that is the same area as the starter?

What was the status before you started working on it? If it was running and now it doesn't, either it isn't getting fuel or it isn't spinning fast enough. I wouldn't get a starter because you would likely know whether or not it was slow if you've been around when it was starting easily.

I'll frequently (if it doesn't start easily by myself) have someone crank the engine while I tighten the injector hard lines after fuel is coming at the injector. It seems to work better with 2 people. I would also have full synthetic in the oil pan if you are any where that it gets cold. Synthetic would be better money spent than buying a starter.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

OK a month ago it was running fine. One cold morning, I could not get it started. I'm 90% sure that the block heater isn't working. To me it sounded like the starter was turning just a little slow. (Still not sure about that point) I practically wore out a battery trying to start it. I had the battery tested and it was starting to go bad. So, I replaced the battery. Still wouldn't start and the starter sounds a little slow to me. Again, that part my be my imagination. I do keep a full charge on the battery.

After the new battery, it still didn't start. I pulled the glow plugs and the #1 cylinder glow plug broke off into the prechamber. With the right tools, it was very easy to pull the prechamber and it looked good after cleaning it and reinstalling the new glow plug. Still not starting. The pre-chamber wasn't excessively sooty. Gave it a good cleaning anyway.

I adjusted the valves. They were not far off. Only had to make small adjustments. Still not start.

I replaced both fuel filters and the primer pump. Filled the twist on filter before twisting it back on. Used the primer pump to bleed the lines. Then made sure there is fuel coming out of the injector pump at the hard line connections. And also fuel coming out at the hard lines at the injectors themselves. Still no start.

You're saying replacing the starter is as hard as establishing peace in the middle east. It was easy with my '65 Mustang

Follow this please.

A video i made for my fiance' as she was on the other side of the world with her om617

https://www.youtube.com/watch?v=Ovnj-vhePGw&t=1s

also, have you tried clutch starting if it's manual transmission ?>

Also, through the glow plug hole put a small squirt of diesel in, just to give it a kick.

Also, your glow plugs, only 1 may be working ? it's the later parallel system. Test each one with 12v to see if it glows, or you can put a dab of oil on them to see them smoke for a better visual indicator.

MATH, That's a good video describing the fuel system. I'm getting good fuel to the injectors though. I've been contemplating replacing the exhaust/intake gasket for a while now. I even have the parts. Is the starter more accessible with the exhaust out of the way? I could do it all at once since I'm wanting to do it anyway.

Those starters are very tough. I think it is just not spinning fast enough. You might try jumper cables from a good vehicle. Your ear will tell you if it is not turning fast enough; it should not sound sluggish at all.

Be sure to press on the accelerator while you are cranking it.

Any chance of a video please, one from within the cabin and another from inside the engine bay as you try and start it so we can see/hear what's going on ?

If you're getting fuel into the cylinders, compression doesn't just disappear overnight.... and with no spark needed....

Have you tested the fuel injectors ?


have you tested each glow plug to be functional ?

have you tested the " line" to each glow plug to see if it's getting 12v.





Wait a moment, this reminds me of the issue i had....

the glow plug relay box wasn't getting 12v. Trace the line back and you'll likely have a break somewhere.

To test this,

1. use a metal coat hanger, long length, or a thick cable...
2. connect 1 side to positive terminal of the battery
3. touch the other end to a glow plug and hold it for a 5 count
4. touch 2nd glow plug for 3 count
5. touch 3rd glow plug for 2 count

6. run into car and turn it over and watch it roar to live, make sure to give it fuel.... I had this problem myself

https://www.youtube.com/watch?v=f_5YILxWtLQ

I had a bad connection and the relay box was making this buzzing sound when the glow plug relay was supposed to be active. The cause of this was a bad 12V line.

One thing that I didn't see mentioned in this thread: Check your grounds. No matter what you do, if the starter or battery have a bad ground replacing parts and tinkering won't fix a freaking thing... Ask me how I know.

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1981 Mercedes 240D - Automatic transmission

Yes, the grounds. especially the flexible one between the chasis and the gearbox/block, that one can become covered in crud and possibly get some crud on the mating surfaces or come loose, Especially if you've had bad motor mounts in the past.

I do have 12v at each glow plug. (1984 series style)