I've searched, but found nothing helpful....
On a '79 CD with loop style plugs, what is required to change over to pencil plugs? Can a controller and harness from a later model be spliced into the original system? Where?

M S Fowler,

I converted my old 190D to pencil (parallel) GP and it started much quicker. I made bushings out of the loop GP in a lathe and screwed the pencil GP `into the bushing an dinto the head. Hardest part was getting out the porceline.

I just ran wires with crimp on terminals from one GP to the next, replaced the resistance wire in the dash indicator with a piece of solid copper wire and connected the in and out wires to the resistance box to the same terminal (thus removing the resistor box from the circuit).

I have heard that replacement parallel GP kits with larger GP threads are available which would make the conversion much easier. However, I don't know where they are available. Maybe soneone else in the forum knows.

P E H

Thanks,
For those of us w/o lathe access ( or skill, for that matter), couldn't bushings be made by tapping thru the center of a bolt that was the same thread, and length as the loop style plugs? Is there any special consideration given to the type of metal used to make the bushing?

that i bough t from jc whitney years ago. i cov=nverted my 220d and the plugs didnt last very long. i dont recommend changing them over. in fact i will give the set i have to anybody... but i still dont recommend it.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

a bigger base to fit the old style heads and wires to convert over. they used to cost about $40 fifteen years ago. dont know if jc whitney still offers them.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

There is a conversion you can buy from parts places online. It is made by Bosch, and costs about $100, and the part number is "0 250 201 955". It comes with new pencil style glow plugs that fit correctly, a new pre-glow relay, and a wiring harness. The kit is meant for a 4-cylinder, but with one more glow plug and a 25amp relay, it will work for a 5-cylinder. I installed it on my '78 300D and it worked great!
By the way, I bought it from "thepartsbin.com." It only comes up when you look up that part number above.

Wired up my pencil conversion on the 77 300d the same way. Worked fine for years. One of the best things to do to an engine with the old loop style plugs.

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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 also strongly recommend this conversion. Somewhere in my shop, I still have a briefly used pencil plug and wiring kit from my old '73 220D (OM615) I'd let go for cheap.

I installed 18MM pencil style glow plugs in my 76 240D.
I used a 82 300D pre glow relay incl. wiring harness.
Retained the gorilla knob and replaced the salt shaker with a indicator light.
Works great.

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76 240 D. Bought in 1998 for $25.
85 300D. Got it for free with a bad engine. ( Sold )
60 Unimog 404. What was left of it, was given to me. Now powerd by 617A.
88 560 SEL. Bought without engine and trans. Now powerd by 617A.
67 250 SE. Cuope. For resto or sale.
64 220SE. For resto.

Same here, just did it on my '79 300D. Starts on the first crank after 15 seconds or so of glow on a 35ish degree pre-dawn morning. Big improvement over the old style.

If your Original Glow Plug Relay works with the set-up all you need to do is replace the Glow Plugs, make sure an 80 amp Fues is in the Fuse Holder, get rid of the Ground Strap from the old system that you do not need, install the Adapter Plugs (80035 I think is the part number) and make the Jumper wires.

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84 300D, 82 Volvo 244Gl Diesel

the only thing i can add to the setup is change the single 10 gauge wire to 4/5 long sections of 14 gauge wire and instead of loops crimped on, crimp on forks, or at least cut the end of the loops so you don't have to remove the nuts to change the plugs.
then hook the 14Ga wires to individual fuse holders with 20 amp fuses for each plug.

this is a little more time consuming, but 10 gauge wire is difficult to get solid crimps to stay on, and 14 is easy. also, 14 is less expensive to buy, and makes it easy to test which plug is dead or failing when they go bad.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

advance auto sells a 6 circuit fuse block you can feed with a single #10 wire and set individual fuses to each circuit... really smooth looking and functioning!

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!