1982 300 TD (Turbodiesel Wagon)

Wagon won't start.

Glow Plug Light on instrument panel not lit.

Checked strip fuse in relay, and found it to be burned through.

Pulled the large connector off the five terminals of the glow plug relay.
With negative multimeter lead on battery negative, and positive lead on each of the five female connections on the large connector, I read:

1 2.4 Ohms
2 2.0 Ohms
3 2.5 Ohms
4 2.4 Ohms
5 2.3 Ohms

NOTE: When I touch the leads of my multimeter together to "zero it", it reads 0.3 Ohms. So this value, 0.3 Ohms, would have to be subtracted from the above readings.

As an experiment, I removed the wire from No. 1 Glow Plug and tested the wire only: negative lead on loose end of the wire meant to go to Glow Plug No. 1 and positive lead on female connector No. 1 on large connector at Glow Plug Relay : Results: 1.3 Ohms less 0.3 Ohms = 1.0 Ohms. Is this about what we would expect for the wire only?

Again, as an experiment I pulled the No. 5 Glow Plug and read it out of the engine. Results: 0.8 Ohms less 0.3 Ohms = 0.5 Ohms. So it looks like that glow plug, at least is OK!

Thinking that the Glow Plugs are OK, I reasoned that it must be the Glow Plug Relay. I ordered a new Glow Plug Relay. After installing it, still got no Glow Plug Light on Instrument Panel AND IT BLEW TO 80 A FUSE in the new Glow Plug Relay.

I would be grateful for any ideas anyone may have.

 

Disconnect wires at GP, check each wire to ground? I'd be looking for a dead short to ground.

When I had my SD, I replaced GPs every year. If you don't find an apparent short in the wiring to the GPs, I'd replace the GPs. That's really all there is in that circuit that I remember.

But get a second opinion.

 

Thanks for your reply, Fred.

You suggested I test each Glow Plug and wire from the Large Connector in the Glow Plug Relay.

That's what I did and reported in my Post:

"Pulled the large connector off the five terminals of the glow plug relay.
With negative multimeter lead on battery negative, and positive lead on each of the five female connections on the large connector, I read:

1 2.4 Ohms
2 2.0 Ohms
3 2.5 Ohms
4 2.4 Ohms
5 2.3 Ohms

NOTE: When I touch the leads of my multimeter together to "zero it", it reads 0.3 Ohms. So this value, 0.3 Ohms, would have to be subtracted from the above readings."

That's why I'm so perplexed! The 1.7 Ohms to 2.2 Ohms (adjusted) is higher than the 1.0 Ohms, or so, we are looking for, but it's hard to imagine that the 1.0 Ohm or so higher resistance on the Glow Plugs would blow the 80A fuse, isn't it???

The No. 1 Glow Plug I removed was somewhat "siezed" in the cylinder head by the carbon material (coke?) tightly packed around it. I wonder if that carbon buildup could in any way contribute to the blowing of the fuse?

-Bill

 

With the glow plugs diconnected from the wires, does the fuse blow?

may take a few fuses to figure this out, but I am guessing at least one bad glow plug, when current is applied, resistance may drop.