So, the glow plugs on my 72 220D worked when I bought it, but they stopped working yesterday. Car has loop plugs and the resistor leads in between the plugs.

I can't decide if I should put in 4 new loops, or if I should upgrade to pencil plugs.

To do the pencil upgrade do I need a different relay? (I tried searching this and people keep talking about manual glow conversions, this is an original paint 47k mile car, I do not want to do a manual glow conversion) I want the car to glow with the starter knob and I want the salt shaker to glow. Will the salt shaker glow with a Pencil plug conversion?

My understanding from googling is I just need 4 pencil plugs, and to make new jumper wires from plug to plug to wire them in parallel, and then remove the ground strap from the last plug.

Insights are appreciated.

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68 280SL - 70 280SL - 70 300SEL 3.5 - 72 350SL - 72 280SEL 4.5 - 72 220 - 72 220D - 73 450SL - 84 230GE - 87 200TD - 90 190E 2.0 - 03 G500

Nissan GTR - Nissan Skyline GTS25T - Toyota GTFour - Rover Mini - Toyota Land Cruiser HJ60 - Cadillac Eldorado - BMW E30 - BMW 135i

I know nothing about the 220D but a google of "220D glow plug wiring" turned up this see post #25 http://www.peachparts.com/shopforum/diesel-discussion/262079-73-220d-glow-plug-problems.html

The salt shaker cannot be wired in series to the pencil glow plugs (which are wired parallel) because it will limit current to the glow plugs and they won't get full power thus not hot enough to start. You cannot wire the salt shaker in parallel to the pencils either because you will likely burn the salt shaker out the first time you try it. What you need to do is wire the salt shaker in series with a resistor to limit the current to prevent it from burning out. The resistor value (resistance and wattage) should equal the series glow plugs + series resistance wires.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Contrary to the above post, you can indeed wire the new pencil plugs and still use the glow indicator ("saltshaker"). I converted my 1968 220D about 6 months ago and only changed the plugs and made new jumper wires. I have been driving it daily since then and there are no issues what so ever. you will be amazed at how fast you can start the engine and a bonus is that your hand doesn't get tired from holding out the starter knob. all that being said, I am very careful when I glow the car, the most I have ever glowed it for is 8-1- seconds and that was when it was 40 degrees outside. depending on engine health,it should only take about 5 seconds to glow with a cold engine. just as a reference, I used the bosch 80035 plugs. keep in mind if you don't like it you can always change it back, whereas that is not the case when you change all the wiring with it...

If you buy the loop type , make sure you buy BERU made in Germany or Ireland.
(*epay has them occasionally $15 each)

If you buy Bosch, look for those made in France.

Forget about any plugs made in India etc..

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1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

I made those comments based on looking at the wiring diagram. How do you have the salt shaker wired? Not questioning what you have works since it gets your car started.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Thanks for the insights so far guys.

I am inclined to just throw fresh loops back in it, the car will only be driven in the spring and summer. Also, many online supplier shows the pencil plugs to be out of stock...

I do like the idea of a faster glow and more reliable which is why I am considering doing the pencils and re-wiring. I need to see if I can source some 80035s.

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68 280SL - 70 280SL - 70 300SEL 3.5 - 72 350SL - 72 280SEL 4.5 - 72 220 - 72 220D - 73 450SL - 84 230GE - 87 200TD - 90 190E 2.0 - 03 G500

Nissan GTR - Nissan Skyline GTS25T - Toyota GTFour - Rover Mini - Toyota Land Cruiser HJ60 - Cadillac Eldorado - BMW E30 - BMW 135i

For what it's worth, when the plugs in mine go out I'm going with the original loop style. They were in there when I bought the car, so there's no telling how old they are. They haven't given me any problems over the last 3 years/30kish miles.

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1963 Ford Falcon Convertible
1972 220D 4-speed
1986 190D 2.5 5-speed
1999 300D

Everything is stock, the only wires that are not factory is the small jumper wires between plugs.

+1 for the pencil style glow plugs.
I would not even think twice. The loop style are so inefficient also if one fails, and it is cold outside, you won't be able to start.

The car starts much faster with the pencil style. There is no issue with keeping them on for a few extra seconds. Their current consumption drops as they heat up (internal resistance increases). In a 300D Turbo, the glow plugs remain on for a couple of minutes after the car has been started - there is a timed relay which clicks them off after about 2 minutes. This helps it idle smoother and have more complete combustion while cold.

1970 220D and 1983 300D

I made the conversion to the pencil style plugs in my 1972 220D 2 years ago by just changing the plugs, creating jumper wires between them, and disconnecting the ground strap.

The plugs are powered by the factory connection coming from the salt shaker with no other modifications.

It has worked flawlessly for 2 tears but reading this makes me nervous about the longevity of the salt shaker and the gorilla knob internals in that configuration.

Also, Funola's comment about the salt shaker limiting the current to the plugs makes sense and I wonder if I'm not getting the full effect of the pencil style plugs because of that.

Last year I installed the same plugs on a neighbor's 1976 300D. His glow plug relay had failed so we wired up the new pencil style plugs using a small momentary switch and a Ford starter solenoid. The system works well.

I would like to install a Ford starter solenoid in my car wired between the salt shaker and the first glow plug. If I'm thinking about it correctly, this would allow all the controls inside the vehicle to function as normal, the glow plugs would get full current, and the stress on the expensive components would be minimized.

In your case though, if it's a warm weather car, I'd stick with the loops. They look cool!

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1972 Mercedes-Benz 220D
www.mezzo200.com

noahlambert, whether the salt shaker limits current to the pencil glow plugs or not depends on how the pull starter switch works. I can't really tell from the stupid German wiring diagram.

One simple test you can try is disconnect one wire on the salt shaker and try a cold start. If it does not start, you know it is in series with the pencil plugs and is limiting current.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Bosch made in India failed in less than 1K miles on my '70 220D.

Some info from Diesel Giant on pencil GP's.

Back to the* Mercedes Diesel parts for sale

in this arrangement, the proposed resistor would flow current and produce heat equivalent to the glow plugs.

does anyone know the saltshaker's resistance?

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'77 240D, 504H, OM617.952, etc.

MB doesn't describe the resistances of the salt shaker resistor because it changes so much as its temperature changes. In the FSM, they say the voltage drop across each GP (when in series) is ~1.25V or less (so 5V total), and the voltage drop across each bendy metal connector is 2.6V or less (so ~5V total). They suggest that the total voltage available during operation of the GPs is 11V, so we have about 1V loss across the salt-shaker (aka glow plug resistance control). I would guess its resistance is about the same as the other GPs, as others have suggested.

One detail regarding the wiring diagram which may be of interest. During preglow, yes the salt-shaker is in series with the 4 engine GPs, so it is effectively acting as a 5th GP. But when the starter is engaged, the current bypasses the saltshaker and only the 4 GPs are in series.

So for Noah and others who have kept the saltshaker with parallel plugs, it is reducing current during preglow. But when you are operating your starter, all the GPs are getting their full current.

Normal current through the series salt shaker is 50-55 amps. That isn't much different from the total current through the parallel plugs. So that is why folks are having decent luck with keeping the salt shaker with parallel plugs. I don't think there is significant reason to worry about longevity of the salt shaker or gorilla knob internals by doing a simple conversion to parallel plugs. The overall conditions aren't terribly different.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).

great post, shortsguy1.

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'77 240D, 504H, OM617.952, etc.