Got a multimeter, went to test my glowplugs a la Diesel Giant's tutorial, and can't stretch the negative probe to the battery and simultaneously test the glow plug ports (they are on opposite sides under the hood). What do you guys do, use an extension wire wrapped from the negative post to the multimeter?

Little obstacles....


I'm pretty sure my glows are in a bad way; it was 40 degrees today and I had to crank three times, 10 to 15 seconds each, before it would turn over.

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JBG
1985 TD wagon, 228k
running on grease since 3.07
AUSTIN, TEXAS

You can use a wire with alligator clips to extend the negative lead to reach the battery. Or, you can just find a clean place on the engine block to touch the negative lead.

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Joe

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1980 300SD - 495k miles - 'The Ambassador'
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Well, I had two multimeters so I took the cord off one and hooked it up to the existing one as an 'extension'. Worked well.

I would think you could also just put the negative pole on something that is grounded, such as bolts on the engine block. I believe the reason they have you put it on the negative terminal is so that you are 100% sure you have a good ground.

You don't HAVE TO ground out the multimeter on the battery, you can use any good ground. The readings you get may not be as precise, however as in my recent case, it doesn't really matter how precise you're resistance readings are when 3 GPs are completely open (infinite resistance). If you have some GPs on the brink of acceptable resistance you may want to ground directly to battery to get a more reliable reading.

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'85 300td Frybrid WVO Kit

I can't get a reading so far....I've tried putting the negative cable on about a dozen different places all over the engine, while keeping the positive lead inside the glow plug connector #1. Any ideas?

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JBG
1985 TD wagon, 228k
running on grease since 3.07
AUSTIN, TEXAS

got kind of a sketchy reading on port #1--meter jumped around, kind of oscillated between 1.4 and 1.8. Nothing on the rest. Guess I'll try to jerry-rig some sort of wiring to the battery, just to get a good ground.

This seems like it's just as much work as replacing the glows--though I've never done that and the #5 plug looks like a tough one. What tools do you need to disconnect the wire and unscrew the glow plug itself? Haynes says "a suitable wrench". Any way to get more specific on that?

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JBG
1985 TD wagon, 228k
running on grease since 3.07
AUSTIN, TEXAS

Sounds like you are doing something wrong. Ground your negative lead although it does not mater if it is the negative or positive lead. Touch the other lead to some other grounded point. Or touch the two meter leads together and mention on site what is indicated. Might be a start for others to help. It is still the easiest way to identify burnt out plugs usually.

Just bought some 12 gauge wire to extend my negative lead to the battery. Will go test with that solid ground tomorrow.

When I touch the leads together the meter jumps around, finally oscillating between .1 and .3. It never settles on a value.

This isn't rocket science, so I'm wondering what is going on....

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JBG
1985 TD wagon, 228k
running on grease since 3.07
AUSTIN, TEXAS

You either have a really wide 123 or really short wires on your multimeter. I put the multimeter in the middle of the engine. I stick the black wire in the ground connection. I stick the red wire in the plug.
Mine reads .4 when I hold the wires together. When I test the plugs I get 1.0, so I subtract .4 from 1.0 and get .6, which is good. I have an analog one too, but I like the digital one better. Some day I'll get a really nice one that can zero out.

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1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

My $15 POS digital meter seems to work OK, it reads 0 ohms when I touch the leads together and someplace in the 0.5 to 1.0 ohm range on a good GP, close enough.

I just use short open end wrenches on the GPs, if you want to get fancy, buy a ratchet wrench.

I just ground to the head when i ohm plugs. I use a $20 Radio Shack meter which works well enough for that.

For removing wires and plugs I use 8 mm and 12 mm combination wrenches respectively. Some folks find it easier to remove the injector lines before attempting to change plugs. I don't, but I have pretty small hands.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.

a ratcheting wrench is wonderful for removing and replacing GPs.

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'79 300SD
'82 Chevy Chevette diesel

I use the bolt that holds the relay on the fender. I also use gear wrenches.

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83 SD

84 CD

I used the 8mm open end wrench for the nut on the GPs, then either a 12mm wrench or socket on the GPs depending on what was easier to reach them with. I just changed all 5 in my 300SD yesterday, took about 2 hours. (Tom if you can change them all in 20 minutes you need to be on a pit crew!) Wish I had some ratcheting wrenches. I'll pick some up at Harbor Freight next time, $8.99 for a set! The GP next the firewall is difficult to reach. Hope you have small hands!

John

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Certified Registered Nurse Anesthetist (CRNA)
2002 F250 powerstroke with Plantdrive WVO conversion
1983 300SD 190K miles ,sold
2006 E320 CDI

Grounded at the battery thanks to some alligator clips and 12 gauge wire. Meter finally produced results. I tested at the glow plug connector. Here are the results.

GP 1 = 1.5 ohm
GP 2 = 1.3 ohm
GP 3 = OL
GP 4 = 1.4 ohm
GP 5 = OL


Then I reached in and tested at the plugs themselves--or as close to touching the wand to the plug as I could get. With this test, both plugs 1 and 2 were the same, but plug 3 gave me 1.3 ohms, while plugs 4 and 5 didn't register anything.

Does this point to the harness (wire that goes between plug and relay, right?) for plug 3?

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JBG
1985 TD wagon, 228k
running on grease since 3.07
AUSTIN, TEXAS