Over the last month or so my '85 300TD has been very hard to start in the AM. At first I thought it was the cold weather and the biodiesel, but I filled her up with straight petrol diesel and ran about half a tank thru with that. Still hard to start in the AM.

Then I parked the car in the garage over night. Stays pretty warm in there but it was still hard to start.

Thought maybe a fuel issue so I changed the pre-filter (maybe I need to change the primary fuel filter too).

Once I'd get it started, the car would run fine. Although it would belch a bunch of smoke during the hard start, it did not really smoke once it started running.

Anyway, now I can't start it at all.

Is it possible I've got a glow plug problem? How would I troubleshoot that? Any ideas are welcome.

Thanks -Harv

Sounds very much like a glowplug issue.

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Nick
*****
2002 Sprinter 2500 140" High Roof :

I agree, use a multimeter set on ohms, pull the plug on the relay, a black box on the driver side inner fender. The GP #'s will be listed, check one at a time by touching the red lead to the numbered female end at the plug, ground the other lead. I use the top of the power steering pump. You're looking for readings below 1. Does your GP light on the dash act any different?

Mercedes calls the clear in-line filter the primary filter, the secondary being the spin on one. You may want to change that one out also, if you do, fill the new one with fuel before installing, you won't have to pump the primer very much.

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83 SD

84 CD

+1

thanks for the thorough advise. I'll check the glow plugs via the relay tomorrow (when I have more energy!).

Thanks also for the clarity on the fuel filter terms and for the advice of filling the secondary filter.

-harv

Hi,

Just wondering how did you go? Did you get it going yet?

Regards,

Fitian

Yeah, I did the test and plugs 1, 2, and 3 look shot (don't get a reading at all). Plugs 4 & 5 return a reading of .5 - .7

Now I've got to order the parts and hopefully I'll get this done next weekend....I'm slow.

I'm trying to decide if I should do the job off of my Mercedes Shop Manual and the DIY articles here. THere is also a $33 DVD from Diesel Giant that looks pretty good for someone like me: I've never done this job, and I'm only moderately mechanical.

Thanks -Harv

Swapping GP's, not difficult. In your case you may want to remove the metal fuel lines, more room that way. You may want to move some throttle linkage out of the way also.
Take pics if you can first, just in case.

Remove the electrical connection, remove GP, reinstall.

The trick is patience.
Have tools, and a telescoping magnet.
Save your money, and learn how to wrench. Nothing more satisfying than accomplishing something you thought you may not be able to do/figure out.

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83 SD

84 CD

My 300d was having a very hard time starting or rather not starting for the last few weeks. The glow light does glow and the engine does crank over.

I just replaced all 5 glow plugs this weekend and it starts like a charm. The replacement took me all day! Yikes, mainly because I didn't quite have the right tools.

Here are the tools you'd need to make it a lot easier:

1. RACHETING WRENCH! in size 12 for the gp (cost about $40 to $70 for a set. these do not normally come in a combine tool set purchase)
2. size 8 wrench size for the electrical nut.
3. sockets in the 8 and 12 size and definitely the smallest of those angled socket adapter and a socket extension!

I lost my angled socket adapter (which I purchased specifically for this purpose!) and I don't have any racheting wrenches. Using just normally wrenches was time consuming!

I didn't remove the fuel lines. I only disconnected some of the throttle linkages. This job is not difficult if you have the right tools! I'm going to acquire these racheting wrenches for future use.

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1987 Mercedes 300sdl, 280k mi (daily driver)
1982 Mercedes 300sd, 205k (occupying driveway)
1985 Mercedes 300d, CA, 148+ mi.
1986 Chevrolet suburban, 50k? or 150k? mi, diesel
1998 BMW 740il, 120k mi (for sale)
1999 Honda CBR900RR, 42k
1997 Jeep Wrangler Sport, 103k miles (sold)

You have shown enough skill to troubleshoot correctly; I bet you don't need that CD on how to remove and install the glow plugs. I remove all of the injector fuel injection lines so I have more space to work in other people don't.
Find the Mercedes shop (DIY tab at the top of the page) do it yourself thread/s and see if there is enough info for you. Remember to check the NEW glow plugs before you install them with your ohm meter even new ones occasionaly are no good. I would avoid Autolite glow plugs; I had a set in my car for 3 months and 2 of the tips swelled up to the point that I needed a vice grip to pull them out.

I have found the ohm reading on the gp's to be useless. I tested all five on our 300D at .1ohm, perfectly acceptable (glow light also still came on fine), but the car was cranky as ever starting below 40 degrees, it'd always start, but with a plume of smoke and clattery unhappyness. So I changed out the glowplugs (they were ORIGINAL) with 5 new Bosch Duraterm plugs + the afterglow relay kit. And the starts are instant and smooth, even at 10F and below!!! The engine rotates one time at those temps and fires right off, very healthy engine with almost no blowby at 224k!

Before the new plugs, it'd crank over about 6-8 times at those temps, get going, and misfire on a few cylinders for a few seconds while making smoke.

Vast improvement with the new glow system.

I have had it on my SD as well for years, and its great!

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)