There is a modified relay available from Bosch. I think it's called an afterglow relay and it requires the use of plugs that can handle the extra glow time.

There is also a modification where you disconnect the violet/purple wire which I believe disables the safety shutoff timer so you get extra long glow cycles that continue after the car is started. I haven't researched this much, so I don't know if this is safe or how the plugs actually end their cycle once the mod is implemented.

I just replaced all my plugs with Monark brand plugs, which I've recently heard glow hotter than other brands but have a slightly shorter life (they're also made in Germany). I don't think I need an afterglow system and I'm happy with glowing twice when necessary. Usually 1 full glow cycle suffices, and in warmer weather the "ready to start" condition indicated by the light is enough.

I imagine an extra indicator light wouldn't be too difficult to add. I wonder if splicing one into the plug circuit so would cause any problems? I could only imagine maybe a very slight drain on the power sent to the plugs.

__________________
Chad
2013 Jeep Unlimited Rubicon
OBK#44
"Pleasure in the job puts perfection in the work." - Aristotle (384-322 B.C.)

SOLD
1985 300TD - Red Dragon
1986 300SDL - Coda
1991 - 300TE
1995 - E320
1985 300CD - Gladys
2006 Nissan Pathfinder LE
1998 Acura 3.0 CL

Hey, as all that unburnt fuel builds up in the combustion chamber, doesn't that keep increasing the compression ratio?

My 240D smokes a LOT when its starts and the engine is cold. Its almost embarrassing. I thinks its unburnt fuel, not oil, but I could be wrong...its a light gray smoke and it decreases substantially after running for a few minutes. But even when its warm, it smokes a little at idle, but runs very smooth. By the smooth running, I'm assuming the injectors are spraying nicely, but that's me assuming.

Could my IP be injecting more fuel than it needs to? And why would it smoke so much when its cold? An incomplete burn? I hope this still fits in the physics of cold starting...

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

I've never known a diesel to NOT smoke, run loud & some what rough on a very cold start - except for maybe the very latest engines. Look at all the YouTube videos of cold starts and whether it's an Detroit, Cummins, Mercedes, VW, or Izuzu they all do that. Cold fuel & cold cylinders mean the fuel isn't combusting completely. Hey, the smoke is part of the fun on having a diesel!

So, even though I have a garage and an outlet to plug in the block heater, I left my 240D outside in sub freezing weather all day and started it tonight at somewhere between 18-20 degrees. Glowed for about a minute and it fired up in TWO seconds but of course smoked and ran rough for a few seconds (but it does that even in warmer temperatures). What impressed me is how good it started considering I have quite a bit of blowby, old injectors, the old-style loop glow plugs of unknown age, and around 50% biodiesel in the tank. I think the Mobil 1 synthetic 5w-40 really makes a difference, and of course my battery is good & valves are adjusted.

It sure is interesting to see how much variability there is between cars with the same engines (OM616 & OM617). Some really won't start at freezing, others will start right up below 0F. Of course if you have a chance to plug in by all means do it though, if nothing else you get heat quicker.

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1976 240D "Katja"

Nothing smokes on start up like a 2 stroke Detroit! On a cold, cold morning when we would start up the 8v71 TI's in the Rybovich, OMFG we would fog the marina out! If I owned that boat I would dump those old loud smokey lumps for a pair of Cummins.

__________________
2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

My CAT 3208 would give those Detroits some serious competition.

__________________
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

My wagon starts very well in the cold, very little smoke. And its just about nill at idle. On the opposite end of the spectrum, I get a plume with the 240 starts, anyone who gets in the cloud's way would have trouble breathing normally. So there's a big difference between the two and the 240 is not what I'd consider normal for an old diesel, but then, these are the only two I have experience with. If they all smoke a ton when they're cold, then I guess I just got lucky with the wagon.

__________________
1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

Disconnecting the violet wire does not disable the timer, it does just the opposite-it allows it to continue to run. Ordinarily, the glow cycle is terminated (early) when the key is released from the start position, thereby cutting the cycle short as compared to what it would have been if there had been no start attempt.

There was a thread on this topic last year. I believe the consensus opinion was that the glow plugs cut out once the key is moved from the glow position to the start position.

__________________
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

The consensus of opinion if frequently in error because one person gets it wrong and the crowd repeats "what he said." So instead of acting as a cheerleader for the uninformed masses, why not get out your multimeter (or look at a FSM) and determine for yourself what really happens?

Yes, you're right.

For the record, here's an earlier thread on this issue which also references an earlier comment by Lance who has a push button glow relay and mentions the electrical draw issues of glowing and starting at the same time.

Glow plug timing on 123's

__________________
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

Even the old W114/115 220D and 240D with the knob you pulled out of the dash kept the glow plugs energized during the starter operation - on those cars the "salt shaker" on the dash was de-energized during starting but the rest of the glow plugs stayed "on" until you let go of the knob.

If the glow plugs were shut off, and the car didn't start on the first compression stroke, it wouldn't start from cold iron at all. Cold air, cold steel, cold Diesel fuel = snuffed out glow plugs if they are shut off. The fuel sprays right at them.

Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

I see many references to the cold fuel hitting the glowplugs and cooling them off quickly. I remember someone in a thread suggested keeping the fuel off for the first ~5 seconds of cranking, then shoot it in when engine is turning. Has this actually been attempted, and if so, helped anyone?

__________________
'79 240D 4 speed manual 105k miles

I understand that it allows the glow to continue after the ignition switch returns to position 2 (following a start from position 3). This is in the FSM and owner's manual which indicates to me that if you are starting the safety shutoff is ignored (or extended) and the glow continues as long as you're cranking to start and then shuts off when the key returns to position 2.

What I don't understand is, reports of the afterglow relay and violet mod giving up to 2-3 minutes of glow.

If the relay timer isn't disabled and you're only allowing the normal cycle length to continue after a start, how is the reported extended glowing possible? ... or was it misinformation?

__________________
Chad
2013 Jeep Unlimited Rubicon
OBK#44
"Pleasure in the job puts perfection in the work." - Aristotle (384-322 B.C.)

SOLD
1985 300TD - Red Dragon
1986 300SDL - Coda
1991 - 300TE
1995 - E320
1985 300CD - Gladys
2006 Nissan Pathfinder LE
1998 Acura 3.0 CL

You won't get anywhere near 2-3 minutes with an original equipment relay. All you will get is whatever is remaining of the original glow cycle, which is around 40 seconds, depending on temperature.

The aftermarket Bosch relay will give a 3 minute afterglow, however.

http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1983@@1983&makeid=63@@MERCEDES%2DBENZ@@63&modelid=6232@@300TD&catid=241959@@Body+Electrical&subcatid=241967@@Fusebox+and+Relay&applicationid=W0133-1606169&mode=PA

As designed, the glow cycle is terminated (regardless of time elapsed) when the key is released from the start position. Disconnecting the violet wire prevents the timer from ending the cycle prematurely, since it doesn't "know" that a start was attempted. So the cycle will run for its "normal" duration until it times out. So, the most that you could nominally expect is an additional 30 seconds, plus or minus.

Thanks.

I seems then that the cost of the Bosch afterglow relay would be worth it, compared with doing the "free" violet wire mod, for someone with a rough idle after starting.

__________________
Chad
2013 Jeep Unlimited Rubicon
OBK#44
"Pleasure in the job puts perfection in the work." - Aristotle (384-322 B.C.)

SOLD
1985 300TD - Red Dragon
1986 300SDL - Coda
1991 - 300TE
1995 - E320
1985 300CD - Gladys
2006 Nissan Pathfinder LE
1998 Acura 3.0 CL