Are the Glow Plugs in a 1981 SD slow glow plugs I want to install a push button relay to control the cycling

One of the members said that the Loop style Glow plugs were the slow ones. If you use a 12mm to remove your glow plugs they must be the fast ones.
Have you read the threads on using a Ford type starter Solenoid with a intermittent switch to replace your GP relay yet?
That is what I have on my Volvo Diesel Car.

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84 300D, 82 Volvo 244Gl Diesel

Not sure what you mean by 'slow'. Your car has pencil plugs, not loop plugs. There's a picture on here of ForcedInduction's manual relay system. I believe a manual system is superior. Many don't. No need to change your system if the existing relay is functioning.

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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 got manual plugs on my ford. Wouldn't want one on my mercedes.

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81 300SD daily driver/project
86 420SEL (sold)
85 380SE(in the graveyard)