The last few mornings it has been kind of cold, 39 on the dash this morning. The SDL has been skipping like a SOB, and smoking real bad. Its acting like a glow plug is out, but gives no indication of that on the dash. But that doesn't mean much, the glow plugs in my SD did the same thing. I wait for the light to go out like always and it fires right off, but starts to skip right away like a cylinder or two are not catching. If I rev it to 2k it clears right out.

I'll have to check my records but they are probably going on 5 years old, just over 30k miles. They are Bosch, but Autozoo Bosch. Maybe they are junk?

I think I'll put a new set in this winter, and see if it improves next fall. Or I could just ignore them because I really only need them for about two weeks.

Are Beru any better?

Damn they got expensive, I don't think I paid more than $8 each last time!
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=27Y0R3ZQY2810T2A5I&year=1987&make=MB&model=300-SDL-001&category=All&part=Glow+Plug

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Well, let me know, becuase this is the same issue I have. ( well mine is accompanied by a clakcing sound - and I dont think its nailing - once the idle smooths out.) Oddly, its worse now that I've cut the bio down in the mix. Go figure.

I believe it is very easy to test them with a multimeter. If you pull the large plug near the gp relay it should have a connector marked w/ each cylinder number. If you measure resistance between the connector for each cylinder and ground you should get less than 1 ohm. If it is more or open those glow plugs or the wiring are at fault.

I got Bosch from my local Import Parts Warehouse last week for $6.99. I tested the existing ones with an ohmeter and they tested fine but when I actually glowed the old plugs (outside the car using the battery and jumper cables) and compared them to the new ones, the new ones glowed faster and brighter.
But, I wouldn't necessarily conclude it's the glowplugs. I get similar symptoms on my 85 300Td and changing the glow plugs does not change the symptoms.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

As you know, the '86 has behaved that way for years. It's to the point where it needs 20 seconds of glow no matter what the temperature. It still might kick and bang a bit for 10 seconds or so..........even at 1500 rpm.

My thoughts are that the plugs deteriorate with age and the 603 really needs a good set of hot plugs if you wish to start without a stumble. Or, you can just give it extended glow time which will accomplish the same thing.

Yeah I noticed that as well. I don't bother testing GP's anymore with the meter because they can test fine and still not work that well. They seem to degrade overtime.

Maybe I'll put a new set in this winter if I get a chance.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Yeah mine was very stumbly for a couple of winters and required the full glow cycle, although it always started. At the very end of last winter, even though it had reached the low 60s outside, it just stopped starting. The plugs had tested fine previously, but at that point two tested bad. I had them all replaced ... four were actually bad. After that it started like a gem, no stumbling, although it wasn't that cold after that. We'll see how it goes this winter. I think those suckers are often bad even if they don't test as such.

If it's nasty cold out I give it the full cycle no matter what, anyway.

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

FWIW -

I'm VERY pleased with the factory extended glow kit I installed my SDL last fall. Helps those cold starts nicely.

And, the best way to do the plugs on the 603 is to pull the cruise servo.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

This works on a 617 engine.

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83 SD

84 CD

I usually don't disagree with the experience of the members on this site. This forum has some of the sharpest members of any auto forum I've been on, but I don't believe that the Ohm-meter test is an all conclusive test for ANY engine. Glow plugs have the same function no mater what MB engine they are in.

Here's why the ohmmeter test doesn't work... It will tell if your GP's or open circuited like a dead light bulb. But it WILL NOT tell you if the Glow plugs are glowing at the tip or not. I've had several MB/Bosch Germany Glow Plugs that were most likely originals that glowed near the base of the plug.

And... just because your glow plug is heating, doesn't mean that it's not covered in soot and gunked up. A soot insulated GP does nothing. The reason I know this is because I've had many GP's that passed the ohms test but when I hard wired them (out of the vehicle) with jumper cables, they took at least 20-30 seconds to even begin to look red and it wasn't at the tip.

A good GP will light up cherry red in about 5 seconds (usually less). The only real test is to pull the plug and hook it up. Does it work? Yes or No.

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-E300d '99 350k
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Sold
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-300d Turbo '87 187k miles
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-300d Turbo '84 245k (sold to Dan62)
-300d Turbo '84 180k
-300sd '80 300k
-7.3 Powerstroke Diesel 15P Van 500k+ miles
-190d '89 Non Turbo 2.5 5cyl 240k (my first MB)
Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.

Your 100% correct, I ran into the same problem last winter with my 300SD. It wouldn't start, acted just like dead glow plugs. I tested them all with a meter and they all passed, but they looked original. So I bought another set, and that fixed the problem. If you hooked the old ones up to a battery they just didn't get that hot.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Where does the cruise servo go? I still want my cruise control.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

If Glow Plugs have soot / carbon build up on the tips, can these be cleaned with carb cleaner and function properly?

Also, Can we modify the glow plug relay so that the time is greater? Instead of 1 minute can we have the glow plugs stay on for 3 minutes? or 5 minutes?

This is completely accurate. The ohmmeter test can give some useful information as to whether the plug it totally shot, but it cannot provide any meaningful information as to the resistance of the plug when it is heated.

I'm quite convinced that my old plugs on the '86 have proper ohmmeter readings, but they don't produce anywhere near the heat necessary for a smooth start.

You just remove it so you can have FAR easier access to the glow plugs. It's four 5mm allen bolts as I recall. Maybe 5min to pull it out. The rest should all be 10mm for the plugs.

Don't forget your antiseize..........................

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]