Can't seem to start my 300D (617). The small fuse on the firewall near teh rear of the engine broke. The line seems to be grounded somewhere but I don't know where to start.

Can busted glow plugs cause this? How do I test if the grounded portion is on the engine side or the wiring going into the car.

Help.


Thanks



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94' E280 Euro
85' 300D Euro
87' 250D Euro
77' 300D Euro
Manila, Philippines

I presume the system you are talking about is the 77 300D. The fuse usually breaks because of metal fatigue not a short. The fuse carries a lot of current which heats and expands it every time the system "glows".

The expansion and contraction eventually cracks the fuse.

The wire from the fuse goes to the #5 glowplug. It goes through the plug and goes to the next plug where it goes through and to the next etc., etc. The curved buss bars that connect two pairs of glow plugs are resistors and will glow red hot if the glow system stays on. The system is a series circuit (like Christmas tree lights - one blows and they are all down).

These early systems flowed about 60a continuously while turned on. The newer "quick glow" system have temperature increasing resistance and start at about 120a and quickly reduce to 70+ amps for the duration. This is easily measured with an inductive amp meter right from the wire.


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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician