'82 300CD, pencil type. I used DG's article, and it was easy to find the 'open' GP, just one of those.

Checked one of my new GPs, tip and body, I get 00.00 or .0000 in meg range. The other 4 GPs in the car are 00.00 as well. Tried two meters just to make sure.

Am I simply using cheap meters that aren't sensitive enough, or am I not groking how to do this test?

I've only pulled the one 'open' GP out so far as I can't lean over the car long enough to do more than one per session, and it sho' nuff don't glow a bit with a jump box, while the new one does nicely.

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Eric, CPO, Submarines, retired.
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Define tip. One lead should touch the body of the gp and the other on the threaded end where the wire screws on.

Ya sorry, bad terminology on my my part. By tip I meant threaded end where wire is attached.

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Meters use Ohms Law to measure resistance: R = V/I

The meter passes a constant current through the leads and then measures the voltage. Most meters don't pass enough current through something as large as a glow plug to measure. This can be a good thing in other situations as it keeps you from frying electronic circuitry if you inadvertently use the ohms function.

This is why Ohms measurement is not a very good test for verifying a glow plug. The really true test is to pull it and check it with power applied to see if it actually glows.

CAUTION! as even the slightest contact with a hot glow pug can give nasty 2nd-3rd degree burns. They remain hot for quite a while!

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )

Thanks Sam, glad to know I wasn't screwing up the test!!

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Good test....pulled them pups out and hooked to my portable jumper.

1 no glow no heat.
1 glowed in a small ring where the (electrode?) exits the threaded area on the way deeper into the pre-chamber
1 started glowing at that wrong end and then slowly started working forward
2 glowed brightly at the tip.

All were very carbon packed and didn't want to release when unthreaded.

Reaming tomorrow followed by five new bosch's.

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Eric, CPO, Submarines, retired.
Here's a sig line...
Mine: '68 Corvette LS1/4L65E, 83 240D, 2000 GMC 4x4, 08 FLSTC Anniv
Hers: '72 Corvette 454/4spd, '99 MB SLK, '93 Metro vert, 78 240D, '92 Silverado, '65 Fjord Rustang, '59 Fjord Fairlane, '17 Slingshot.

FYI when you test them with cables....only test them for 30sec....don't over exceed 60sec.....then you will damage the plug....

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Thanks Egon, Important Safety Tip (Ghostbusters).

I didn't get over 15sec, the two 'wrong side' heaters were really apparent quickly, as were the two proper tip heater heaters. The dead one didn't even spark when connected.

I'm not even saving the two good ones as spares, I'm carrying new as spares. $8.50 for Bosch, all 5 old ones are going in the skip.

e

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Eric, CPO, Submarines, retired.
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I have extensive experience with the Harbor Freight Multimeters since the 1980s.

In testing resistance the only difference I can see between a good quality Meter and a Harbor Freight one is that with a good quality Meter when you put the 2 probes together you will get Zero resistance; meaning there is no measured resistance in the Probes or the Probe Wires.

When you do that same test with cheap Meters you are going to show some resistance in the Probes and Probe Wires. If you need an exact reading you need to subtract that resistance you got when you put the Probes together from the reading you get from the Glow Plug.

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84 300D, 82 Volvo 244Gl Diesel

I have two mid-range meters ($60ish), but no flukes. They both zero out probe to probe.

Problem is, they were zeroing out on all but one GP (not when tested via harness wire but when tested connection screw to body).

The one GP just showed open.

Pulling them out, as more than one lister suggested, really told the tale, as one indeed was totally open, 2 were glowing in a small ring at the wrong side (not tip), and two were glowing orange at tip. All my meter could tell me is that one was bad.

Comparing the two that did glow orange at tip with a new Bosch, I'd consider all 5 bad. They were dull and slow compared to the new plug.

The chambers were also quite coked up, I had to run a smaller drill bit in first to make room for the reamer. I removed quite a bit of gunge.

Hope tomorrow's motor mount routine goes as well.

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Eric, CPO, Submarines, retired.
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Hers: '72 Corvette 454/4spd, '99 MB SLK, '93 Metro vert, 78 240D, '92 Silverado, '65 Fjord Rustang, '59 Fjord Fairlane, '17 Slingshot.