The pre-ignition rely/coil that sends the spark to the glow plugs fail to activate some times but it is totally random. Is there some way to activate it manually and/or reset it so it will work normally? Seem that if you can get the car started [in warm weather] then the rely starts working again by itself. But car won't start in cold weather without it!!! Help Please email address firstname.lastname@example.org
1984 MB 300D - Pre-ignition rely/coil some time fails to activate on 1990 Mercedes-Benz 300D
by Visitor in Gibbsboro, NJ on December 10, 2010
ANSWER by Visitor on February 03, 2011
Maybe loose fuse for that circuit. Open fuse box and clean and wiggle fuse and it's connectors. also check for loose wires and or connectors in that circuit.