So my 93 300D 2.5 has been starting rough in the extreme cold here in NC (10-40 F). When real cold, I am getting real missing and white smoke for 10-15 seconds and then it smoothes out and runs good. Glo plug light has been working fine through all of this. However tonight I started it after work and it was 41 F on the dash therm but again very rough start and white smoke. GP light worked fine (came on, started and then off). However after I eased out of the parking space the GP light came back on for about 1 min! Never happened before. Drove fine. I started again twice since and the light was normal.

two questions.

1) If the light works normal (i.e. comes on and then off like normal) can I have a bad GP? I thought the light failed when any of the GP's failed.

2) What's up with the light coming on when running?

I plan to check the GP's and circuits but wanted some thoughts from those with experience. p.s. How hard is the GP replacement on this model car. is the intake hard to remove and re-install?

Intake is not hard (Have a new intake gasket ready) 04diesel changed his with
the intake in place.

You've got one or more bad plugs.
If the #1 plug is out or two or more of the others the glow light will not come
on.

Check all the connections for "Clean + Tight"

[MayBe the Pre-Glow Relay was COLD too and restarted the glow process?]

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'84 300SD sold
124.128

So I checked while cold this morning (car sat in garage in NC overnight, temp in garage probably ~45F). I had 12.24 V across the battery terminals before starting and 13.6V once running at idle after I backed it out so I didn't kill myself with the exhaust. So obviously the alternator is fine, just wondering is the 12.24V cold pre-start enough for the GP's. I read on the dieselgiant that I should have 12.5V and I know a dead battery often isn't too much below 12V. As an aside, my E320 had the same voltage cold pre-start and my F150 had 11.98 after sitting in the frigid cold without starting for 4 days and that batt is less than 6 months old.

My intuition is that voltage is adequate.

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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

I had 2 glow plugs out on my OM606.910. The glow plug would come on after I started the car. It wouldn't stay on more than 30-45 seconds though.
You need to test them for resistance value to get an idea what you're up against. The intake seems daunting until you do it for the first time. Easy to do, just extra steps compared to an OM61x.......

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

Preglow Function

Preglow Troubleshooting



A fault in the preglow system is indicate by the preglow indicator lamp failing to light up when the key is turned into position"2". In addition the preglow indicator lights up for approx 1 minute when the engine is running.
The following faultes are detected:
Interrupt in the cable to connection terminal 30.
Preglow time relay faulty.
Interrupt in one or several cables to the glow plugs.
Interrupt in one or several glow plugs.
Short-ciruit at one or several glow plugs or in the cables.

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92 300D 2.5L OM602 OBK #59

update on my situation. I did the ohms continuity test. GP's 3,4 and 5 have <1 ohms resistance (0.7 or so). I guess that is good. GP 1 has 26.5ohms and GP2 has 13.6 ohms resistance. I guess that is not good. Is that my problem, GP's 1 and 2 are bad? Still I am not completely comfortable that the light is coming on after it is started. It stays on for ~45 secs or so. If anyone has a detailed description (with pictures) on the intake manifold removal I would appreciate it. My worries are what to do with all the crap that hangs on top and on the side of the manifold. Will it move once the bolts are taken out or do I have to remove a bunch of other stuff. I'm hell bent I'm going to do this but timid that I don't screw something up.

All is O.K.
(If you'll carefully reread the advice given by the posters above,under less
stressful conditions,you'll see that the answers to ALL your questions have
been covered...Particularly pay attention to the LINKS in reply #6 above.)

The 45 second to one minute ReLight from the Pre-Glow Light on the dash is normal with the following:
("GP"s #1 + #2 are out of specifications).

If the GP light had come ON and STAYED ON it would indicate the GP Relay was "Sticking".

Do Not Pick Up Your Wrenches EXCEPT to "Change Out" the #1 and #2 Glow
Plugs!(Put some penetrating oil around the Glow Plug Circumference overnight
[To Allow it to Soak in] ...It'll make removing them easier.

This is the Official Glow Plug Reamer Obsession Compliance RELIEF Thread:
http://www.peachparts.com/shopforum/showthread.php?t=76490&highlight=glow+plug+reamer&page=4
You will note member diesel911 "Handcrafts" and merchandises a "Reasonably"
priced Glow Plug Reamer.

The Nut that secure the wire to the end of the Glow Plug is "Captive" ,it is
affixed to the end of the wire.
(I'd have a Magnetic pick Up Stick handy,Though, No telling what the P.O.s
[Previous Owners] have been up to.)

Super Penetrating Oil:https://secure.concentric.com/kanolabs.com/orders/order_kroil.shtml

Stuff rags in the "Bermuda Triangle" just outboard and below the GPs in case
"Something" tries to jump down in there.

Your Pre-Glow Relay is kinda unique in "Mercedesdom". It is Electronic...
If it senses an overload on it's circuitry,It will disconnect itself as a
Lifeguard action.(It resets upon cycling the Ignition Key Off/On. IF the
problem has been corrected !) There fore you will not have the typical
80 Amp Aluminum Strip Fuse inside the Pre-Glow Relay Cover.I have NOT
been able to find a source for NEW Pre-Glow Relays of this type ANYWHERE
on Planet Earth...So Treasure Yours! (All the "Replacement" NEW ones have
FUSES)

Attached Thumbnails

 

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'84 300SD sold
124.128

Well, I'm now half done. I pulled the bloody IM today and it wasn't too bad once I got past the intimidation factor of not wanting to screw something up. The GP's all came out well. No problems once I actually could get a hand on them. SOme say they replace these without removing the manifold, I don't see how that could be possible on a 93, but I'd love to see how. I'm waiting for the new gaskets to come and then I just need to reinstall the manifold. Man that thing was full of crap. I cleaned it as best I could and I'm going to get some solvent and soak it also. I can't see how these cars can keep running not to mention run into the 300K's. This one has 95K on it and I can't imagine by 300K what that intake would look like. Well, on to the hard part getting the gasket and manifold lined up and the damn bolts back in place . One thing is clear, I am not a mechanic, but I do what I can.

If your EGR valve happened to somehow malfunction, that would stop the injection of soot into your intake manifold. When the soot combines with the oil blowby being fed back into the intake to be burned, it makes that sooty-oily residue buildup.

Search here on keyword "EGR" to find out how those darned things malfunction.

Ken300D

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--------------------------
1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

So in the last 24hrs I've gone from a bafoon scared to touch the car to pissed off at all the gunk in the crossover and intake and ready to start modifications to the EGR, but there is a problem, this is the 2.5T model (1993) not the older 300D. I like the idea of a malfunctioned EGR or rather I think since this is a spare vehicle I just want to make it an off-road racer. With all that in mind, I have done some forum reading on the topic and I'm very confused. If I had an older 300D this seems trivial, but I have the 93 2.5T which it seems has a problem if you just block the EGR to intake port. The computer doesn't like that apparently from many posts and kills the turbo boost. Simple question, is there a consensus in all these posts on how to disable the EGR on this model without destroying the turbo boost?

Simple answer!!! NO you cannot disable the EGR and still have the turbo boost...UNLESS you change the Turbo from computer controlled to Pressure Controlled.

HERES HOW!!!! read GSXR post on Modifying the turbo from computer controlled to pressure controlled.

your questions will be answered here!!!!!
http://www.peachparts.com/shopforum/showthread.php?t=212097

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92 300D 2.5L OM602 OBK #59

Yes, there is. Do what GSXR and a few others have done. You should be able to find the write up if you haven't already. If you aren't going to do it, don't spend too much time on the intake. It will just get icky again. You can clean it again in a few years when you change the glow plugs.

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1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

Screw the EDS (Electronic Diesel System[Computer]),it seems like it's only
function is to deny you Boost!

Your reading assignment for the rest of the weekend:
http://www.peachparts.com/shopforum/showthread.php?t=212097&highlight=wastegate+swap

'Very,Very long...GSXR's (And everybody else) tutorial on how to "Loose"
the EGR and all the ancillary Electro/Vacuum crap that "Craps Up" your
engine and the engine bay.

I.E. 1. Replace Vacuum Operated Wastegate with Pressure Operated.
2.Jerk out all that "Rat's Nest" of Vacuum Tubing and Sensors/Actuators.
3.Enjoy a cleaner engine (Inside + Out) and better performance!

EDIT: Beat to the Punch by: bobodaclown + bio300tdtdriver!

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'84 300SD sold
124.128

Thanks, you have confirmed what I thought I was reading about this model. Very enlightening. I think I just need to get a 240D and life will be a lot simpler!