Glow plug genius question!
 

Do you start counting the glow plugs from back to front or front to back?

Inline engine cylinders are numbered 1 through 4, 5 or 6 from radiator back to firewall.

The older GP's in series definitely had a sequence to them, and I'm not sure if that started at cyl#1 or the other way around.

W115 300D: number 1 is at the firewall, #5 is at the radiator. This is the exact opposite of what someone else posted... I am not sure what engine he referred to. Check your service manual for your engine to be sure. I would be surprised if MB reversed this ... But I only have my engine for reference.

w123 1984 300td. Looked in the manual and could not find it... So which is it?

Isn't it stamped on the engine? Pop the hood and look?

Just tried. My engine is very dirty... can't see anything... one day I gotta wash this thing.

On the 617 in the W123 it's front to back - or radiator to firewall - in increasing order.

The info stamped on the valve cover is the firing sequence, I thought it was the cylinder order. See here for a pic http://www.peachparts.com/shopforum/diesel-discussion/294487-painted-om617-valve-cover.html

Much appreciated! That valve cover is BEAUTIFUL!!!

What is about your engine that led you to that conclusion?