Who's got an ammeter that can handle 20A DC............lying around??

Wish I did..........

That's good to know. Does #1 glow plug have a higher probability of burning out?

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I don't see why it would...........?

Murphy says that the most difficult one to reach will always have the highest probability of burning out.

I do. I have 3 of them. Go to Sears and buy their DVM with thermocouple input which has a 20A range. I paid $30 for ea. but price may have gone up a bit. If you don't have a 20 A amp meter, and you have a battery charger with higher than 20A capacity, use that to drive the glow plug and watch the meter on the charger.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I didn't think so either. Just that in this post, many have reported #1 glow plug burned out.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I've got a very good analog meter from Radio Shack but it only handles 10A.

Probably can't justify another $50 meter once every five years when I'd like to measure 20A. Besides, I'd put that meter in unobtainville and it would be useless anyway.

This is the method I use to secure the glow plug nut in the socket. If the paper or plastic is thick enough, that nut won't fall out on ya.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Then get a starter motor clamp on ampmeter. They are cheap. mine is made by Black Hawk. I have not seen them in local auto parts stores but I think JC Whitney has them. I put it in proximity of the wire (no need to break the circuit) that feeds all the glow plugs and put a mark where the needle registers. If it reads lower than that mark, then one or more glow plug is toast, so I move the clamp amp to the individual glow plug wire to find the bad one. Works great! saves time.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Hi. Uh. Lots of messages, I see.

Let me ask you this, .. It seems like everyone on this forum who has the "same" problem as me has a working relay that clicks whenever they turn the key to pre-glow. Is this not true?

Then how are we all even talking about the same thing? I don't hear anything during pre-glow and yet it still starts smoothly. My problem is not the same as Brian's for example because the relay socket for his first GP didn't have a good reading. Right now for me all the sockets are reading fine. It's odd that this issue isn't shared by anyone else.

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1985 300d Turbo, 274k miles
my first and only car

Also how does the ampmeter/ammeter help? If you know the resistance going into the plug by doing the probe-in-the-relay-plug check, and if you know there's exactly battery voltage going into that plug by doing the probe-on-the-pin check, then isn't it clear that you're getting V/R amperes into the plug? How is this check any different?

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1985 300d Turbo, 274k miles
my first and only car

Solo,

Several months ago when I acquired my 84 300TD turbo it had the same problem you describe. No GP dash light, smooth start, all plugs read 0.6 Ohms with a good multimeter. I had to remove each glowplug and test it on the battery (as I already described).

You've verified that the dash light bulb is functional right? If I remember correctly, the GP dash light would work (and time out) on mine when I disconnected the wiring harness at the GP relay.

If you had several GPs out (more than 2) your cold engine start would be noticeably rough. But with only 1 GP out, you might not really notice. And, only GP #1 will cause the light not to work by itself. So start there. Pull the wiring harness (the one that goes to the GPs) off the GP relay and see if the dash light works. If it does, then remove GP #1 and test that it glows red hot on the battery. If not, replace it.

I would probably pull and test all the GPs as well.

Yep, got to give that a whirl next time. Thanks.

Might even get one of those clamp on ammeters as well.

That is a good question. When you are testing with an ohm meter, you are not testing under actual operating condition where an ammeter is (almost). A glow plug gets hot, if not perfect, internal connections can open up (like a thermostat) as it heats up and not glow anymore. This is rare but could happen, especially to ones where the center electrode has spun. Such a glow plug could test good per an ohmmeter but still be bad.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Here's a pic of the Starter/generator ammeter on the main +12 V feed to a 240D glow plug relay.

Note: These type of ammeters are not designed to be very accurate in absolute terms. You have to understand its limitations and use it as such. It is not really a "clamp amp" where the meter acts as the secondary of a transformer (which works on AC current only). I believe it works on magnetism. While I have not taken one apart, I think it is very simple and is all mechanical, no coils etc.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked