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