240D 4 cylinders, 3 glowplugs? - PeachParts Mercedes-Benz Forum

#1 02-09-2006, 11:10 PM

Newbie to these diesels. Just going through my 240D and noticed theres only 3 glowplugs with wires hooked to them. The fourth ( closest to firewall) has no wire connected. I didn't even find a loose wire that would go to it. Any help???

t walgamuth · #2 02-09-2006, 11:19 PM

you will need a wire for it. when it is working you will find much better starts and smoother idling when cold. somewhere the wire has been cut or broken off. find it and splice in a new wire to supply the plug. then use shrink tube to cover the splice. i would solder it together for best conductivity.

good luck

tom w

Diesel Giant · #3 02-09-2006, 11:19 PM

You should have all 4 connected. Maybe this will help.

http://dieselgiant.com/glowplugrepair.htm

#4 02-09-2006, 11:34 PM

Well it might seem strange but the connector that goes to the relay only has three wires in it. Sound like I need to find a new harness? Being new to working on diesels, I have to ask. Does the engine not need the glow plugs to keep running? It only needs them to start?

Addicted · #5 02-09-2006, 11:42 PM

this will be my first post ever to something that really means anything and to answer a question.

First welcome to the forum and your new mercedes. Gotta love the 240s.

Second you only need them for starting. Sometimes not even that but it sure makes it a lot easier.

good luck.

#6 02-09-2006, 11:46 PM

Thanks Addicted.

Stevo · #7 02-10-2006, 01:23 AM

One glow plug out on a four cyl 240 will be very noticable ... you'l really see the difference when you have all four working

It'l idle smoother and not smoke so much after start up.

airbus · #8 02-10-2006, 01:16 PM

Quote:

Originally Posted by Stevo

One glow plug out on a four cyl 240 will be very noticable ... you'l really see the difference when you have all four working

It'l idle smoother and not smoke so much after start up.

...not in Surf-n-Turf's location probably...

It's a different story in the north. But honestly, fix it, you'll have much easier "cold"-starts. It's an easy fix. Buy yourself a Haynes Manual, all basic and some major fixes are described in it.
Welcome to the dieselers.

Diesel Giant · #9 02-10-2006, 07:43 PM

The glow plug is only used to heat the prechamber for starting. Once the engine is started, compression is the ignition source. High compression squeezes the air to about 1900 degrees and then fuel is injected. The high heat allows the fuel to burn. In a gas engine the spark plug provides the heat to burn the fuel and must do so on every stroke. If the diesel engine is in good repair with high compression, they will start without a glow plug.

My Tdi will start down to about 0 degrees without the glow plug working. The Mercedes will not though.

t walgamuth · #10 02-10-2006, 08:37 PM

a glow plug doesnt really apply to us in the great white north.

well they will if not too cold but you dont really want to make a habit of it.

tom w

#11 02-13-2006, 01:35 PM

As I posted earlier, theres only three wires in the harness that goes to the relay. Can I jump from 1 glow plug to another.

t walgamuth · #12 02-13-2006, 01:44 PM

no

sorry

tom w

SD300 · #13 02-13-2006, 02:51 PM

I did jump another wire from another GP. That was done in my old w116 300sd.

Are these individually wired timer. Or else run a wire from another GP to trigger a relay from the Batt terminal that way you wont over load that factory relay.

In my current 77 240D, I use 2 relays and 2 sets of wires to power the PGs.
These older ones runs in series, each use 3 volt, when series 4 together = 12 v.
The existing wiring from fact were not supplying enough juice.
I use a toggle switch inside the car. Our great digital clock has 1 sec per tick, so u can count that as timer. i usually hold her down for 10 secs then click the starter.

Wes Bender · #14 02-13-2006, 02:51 PM

I would try to figure out what gauge wire is being used to go to each of the other three, get some wire of that gauge and run your own wire from the relay to the fourth glow plug. Rather than trying to put it inside the existing loom, you could just fasten it to the outside of the loom with wire ties.

Before you hook it up, I would check the resistance through the disconnected glow plug and compare it to one of your known good ones. That wire might be missing for a good reason. You may need to replace the unconnected glow plug before it will do you any good. (I'm thinking that, if the plug is shorted and the fuse didn't blow, it may have fried that missing wire. We don't want that to happen again. I don't remember the location or size of the fuse on the 240D. Maybe someone else will provide that info.)

Good luck with it and welcome to the forum.

Wes