Note: I posted this question in tech help but it was suggested to post it to Diesel discussion. So I am reposting it.
Thanks.

I live in rainy Vancouver, BC and have been having problems with the glow plugs on my 1977 300D

My glow plug light wouldn't come on and car wouldn't start(It is currently cold and wet).

I found the "first" one in the series had burned out(loop style). Replaced them all because I haven't done it in a while. About a month later had the same problem. Have replaced the first plug a couple of times now.

What could be causing the first glow plug to keep burning out?

Also, should I replace the ceramic insulators as some have small cracks?

dristar,

Did you check the voltages across the GP like I suggested?

P E H

Yes thanks.

I had the car parked for a day after I changed the first glow plug and then everything seemed to work fine.

I did check the voltage across each glow plug and it seem to be fairly consistant. Also I checked the resistance wires and they all have same resistance.

Everything is dry now and I suspect moisture may be one of the issues. When I removed the relay and there seemed to be some moisture under one of them. Could this be causing the glow plugs to stay on too long and burn out?

Also, shouldn't the bus fuse protect the glow plugs. Shouldn't it burn out before the loop glow plug?

Can carbon in prechamber cause glow plug to short out? If yes how do I get rid of it without buying a "reamer tool"?

Sorry I'm rambling and thanks for your any other trouble shooting tips you may have.

I suppose a GP could be shorted inside the Pre chamber but it would take a helluva short to carry enough current to burn out a GP. Maybe you could remove the injector and take a look.

Or remove all the wires to the GPs and do a resistance check on both terminals of each GP, to ground.

P E H

dristar,

I just thought of something. When you said first GP in the series, I thought you meant GP in cylinder #1. But it could be the GP in Cylinder #4. Which GP is it. It is more likely that the GP in cylinder #4 would burn out from a short in another GP than the GP in cylinder#1 because #1 has one of its terminals connected to ground.

P E H

When I said first glow plug I meant the first one in the series which is probably cylinder #5.

Now unfortunately the car will not start at all. Pulled out all the glow plugs and they are all fine. Will try replacing the resistor wires and see what happens. Also, I am currently recharging the battery to see if that helps.

Any other things I should try? Could it be bad fuel?

dristar

I battled this hard starting thing with my daughters 240d, then I broke down and got the new style, fast plugs, NO more problems....do yourself a favor Forget about those resistor wires.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Had the exact same problem the same year car. What I did was pull the plugs and used a small magnet to fish out any small metal fragments. What I got out were tiny pieces of melted metal. I mean tiny as in little specks from the old plugs that had melted. Then I turned the engine over several times to blow out anything I may have missed. No more problem.

Here is a quick test you can do to see why the series plugs are burning out. Thread a new series plug into the problem cylinder and measure the ground between the threaded tip and the engine. There should be none. Now try wobbling the plug back and forth. If you see continuity as you do this, there is something inside the chamber grounding out the new plug. Maybe carbon or melted blobs from the previously burned out plug that was in there.

I did what Stevo did and updated to the parallel type. They cost the same and don't ground out in the chamber.

Dristar,

I think what 300SD Driver means is to check, using your ohmeter, from either terminal of the GP to Ground to see if there is any continunity as you are screwing in the GP which would indicate that the GP "loop" is touching something inside the pre-chamber that could be causing a short circuit.

P E H

dristar, you've got one of two issues if the same plug is "burning out". The first is a drippy injector. I call it the first because it's usually the last thing people think of, and by that time they're pretty frustrated. You either know or can search for the drill on that issue. Bottom line is that a drip of "cold" fuel on a hot loop will result in a loop with a blown out portion and probably a chunk of metal (loop) in the prechamber.

The second issue with a burned out loop is a short downstream of the problem plug's loop, since it's a series system. Yes, a cracked ceramic will create a path, so replace them. Yes, it's very easy for carbon to short a loop style plug, so ream the holes. Your car probably has a coolant sensor at the far downstream side, so check it for proper operation or bypass it.

After those drills are done, you then need to check the relay. I don't have any first hand experience there but the diagrams are on the CD I bought from this web site.

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daBenz - 1970 220D

I do seem to be going through oil at a higher rate than normal. What could be causing this and how do I fix it before I have real (expensive) problems?

You could also be burning engine oil in that cyl which can eventually take out the prechamber and destroy the head.

Peter

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Auto Zentral Ltd.

Autozen,

Of course he's burning oil in that cylinder and in the other cylinders too because its a Diesel and designed to burn oil.

P E H

Dristar,

Two reasons for burning oil in one cylinder are a cracked head that is leaking oil into the combustion chamber and a broken ring.

Cracked head usually only applies to #1 cylinder because that is where the the oil passage is that takes lubricating oil to the camshaft and followers.

Broken ring can usually be found by a compression or leak down test.

P E H