hi folks,
i looked and one link says that number one cylinder is the front of the engine, number 5 is a pita because it is the one under the heater hose.

But the valve cover says "1,2,4,5,3"

Which is the real order for a 1980 300CD (smaller pencil type plugs)?

i also assume that number one and front of engine means nearest the fan.

Also, the diesel giant page for checking shows the large connector as having 5 leads for testing, simple. But my large connector at the relay has 7! though it does say G1,G2 ect up to 5 so I am guessing the other two leads are sumthing else...

any help is greatly appreceiated

__________________
Think Alternative Energy!
300CD '80 (now gone but not forgotten...)

That's the firing order.

The cylinders are numbers in sequence..........1 is in the front.

Ah, of course. I should have know...

Thank you much, Brian.

__________________
Think Alternative Energy!
300CD '80 (now gone but not forgotten...)

Nein,nein,nein, If the germans did not want the glow plugs wired up in the firing sequence they would not have marked the valve cover. No wonder most these diesels are only averaging 40 mpg.
Thanks for the new twist by the poster as I had thought about every possible question ever asked about the glow plug system had been already covered over the years. On this I was obviously wrong.
Obscure questions sometimes lead to discoveries or ideals no one else has ever considered before. Some ideals are questionable, impractical, flawed, and once in a great while applicable. If you strike out twice and connect only once for example all is forgiven. You do not have a chance at all unless you are in the game.
Some good ideals have been lost to history. So I am always interested in others perceptions of things myself. It makes me think. I enjoyed this one.
For example no one to my knowledge has ever considered going to a pulsed power glow plug system. The electronics (cheap high current reliable solid state almost self standing devices) where too involved and expensive if even existing for normal production and servicing in the distant past when 123s were in production. On the newer diesels there is absolutly no or very little requirement either.
Yet there could be a major upside for the older 123 series. The glow plugs tip temperature might be elevated quite a lot without burning out the element. Or a lot longer heating effect without dropping the battery too far. Actual plug durability could even benifit. It is the element that eventually oxidizes on a time used basis. An element is so slow acting the thermal shocks of pulsing might even be inconsequential.
Might require a new type of engineered plug . Could be doable or explorable. Who really knows unless literature from the past or current unused knowledge is investigated? I might drop a note to the glow plug manufactures as I imagine they have played in this area.
They never would have considered upgrading these old systems in retrofit as their parts sales are not affected and it is not their cars that will not start when it is cold enough.
Again thanks for mentioning a firing order for the glow plugs. Otherwise even getting to consider an unusual approach with all it's apparent pitfalls and possible benefits might never have surfaced. One never expects anything to come of approaches like this really but sometimes they do or indirectly lead to other avenues.

I always assumed the glow plugs all heated at the same time while the glow plug light was on. The order - injector squirting order?
Charles

I guess we can give you a pass...being from Canada and all but here in the States (and the rest of the free world for that matter) they are known as "Ideas" instead of "Ideals"....

Fair enough and thanks for the leeway. I really do not get enough time to catch all my errors. You gentlemen on site are just great.
.