Good morning

A couple of weeks ago, while I had my injectors out for bgkast to rebuild them, I decided to go ahead and replace my glow plugs as I had no good idea when PO had done this. Prior to this (PO glow plugs), my first AM starts were a little rough (stumbling, smoking for a few seconds after starting), but these symptoms improved if I used longer glow cycles. Anyway, since I had access with injectors out, I removed old plugs, reamed holes, replaced with 5 new Monark plugs, and went ahead and replaced relay with new Monark relay.

Since re-installing everything, my first AM starts are MUCH rougher. Even with prolonged glowing (20-25 seconds, probably not to "click" under hood/dome light re-brightening every time, but longer than previous routine), I have to crank for probably 5-8 seconds or so, with worsened stumbling/smoking for first few seconds after ignition. After this, things smooth out and are fine. On the road performance with new injectors is noticeably better. Warm starts are fine.

Today, I have been working through the DieselGiant testing procedure. I have 12 volts DC at battery, 12 volts DC at each end of relay strip fuse, 12 volts DC at "hot" line arriving at relay. When I tested resistance at each contact in GP harness "plug", I got 0 ohms at each point. I, perhaps incorrectly, interpreted this as "no resistance, good result".

I went ahead and removed all of my plugs. I have 12 volts DC at each harness connection to individual plugs. When I test each plug for resistance, I get 0 ohms for each; DieselGiant suggests that this means that each plug is "shorted internally".

Does it seem likely that I bought 5 "new" Monark plugs that are all bad? I am concerned that I am misinterpreting my testing results, or am just not testing correctly; I understand the concepts of resistance, voltage, and current, but don't have a lot of practical experience with the multimeter (choosing from the various scales for reading resistance, for instance). For example, how can you really test the resistance through the individual plugs when they are out of the engine and in you hand, with no externally applied current?

I appreciate any thoughts that any of you have.

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1982 300cd, 140k miles

Glow plugs should have about 0.6 ohms of resistance. A truly "cheap" meter may not have enough resolution so that would be my first question. Have you checked the old glow plugs? Compare them to the new ones. If the glow plugs really measure zero ohms then they are bad. I have no experience with your brand of glow plugs, having always used Bosch. I recommend putting the old glow plugs and relay back in the car and see how it starts.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Sorry to admit it, but I threw them away. The tips were worn down and they were covered in carbon, and I couldn't think of any reason to keep them. Oh well, another lesson learned.

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1982 300cd, 140k miles

After re-reading the directions that came with my multimeter, I probably was testing the plug resistance with the wrong scale on the device. When using the "200 ohms" scale, I get 0.6-0.8 on all plugs; that seems more appropriate.

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1982 300cd, 140k miles

OK, then the plugs are good. Did you also throw away the old pre-glow relay? If you still have it, put it back and see what happens.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Jeremy, you're making me assume too much guilt. Yes, I tossed the old relay too; I did think about keeping it before I did though.
Anyway, I've tested all of the components as best I can understand with DieselGiant and FSM as guides, and everything checks out. By this point, I have run so many glow cycles that I'm no longer able to reproduce the conditions of a first morning start. Thanks for your thoughts, and I'll keep working on it as I have the time.

Ross

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1982 300cd, 140k miles

Could have an air leak. Try pumping the primer pump 40 or 50 times before starting when cold and see if it makes a difference.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The Monark GPs are not considered the best quality. However, I have them in my Engine. I glow everytime I can remember to do so but it is not cold here in Southren CA. So far none of them have failed and it has been about 1 year since they were changed.

Some Member believe that the ultimate test of a Glow Plug is (if the plug is out of the engine) use a Jumper Cable cliped on one terminal of the Battery and grip the Glow Plug terminal with the other Jumper Cable Clamp applying the threaded area of the Glow Plug to the opposite Battery Terminal to see of the actually get Red hot like they are supposed to.
The reason is that on occasion a Plug with a good ohm reading will not actually heat up.

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84 300D, 82 Volvo 244Gl Diesel

The current is supplied by the meter.

Thanks for your replies.

kerry, I hadn't thought of the air leak. I can try pumping the primer this morning before I start it.

Diesel911, I had read about "testing" the GPs in that way with jumper cables (or "jump box" on DieselGiant pictorial). I tried it on a couple, and they got hot and started emitting wisps of smoke, but never glowed bright red. I realized I was conducting a test that I didn't fully understand (how long to apply current, did it matter which polarity from jumper was touching which component of GP, etc), so I just stopped. Maybe the Monark plugs are just poor quality. I read the propaganda on another site about how good they were, and there seemed to be a mixture of opinion on here about the other choices, so I went with these.

tango, thanks for clarifying that. It certainly seemed that there had to be some current applied from somewhere, the resistance to which the meter was reading. So, in the end, I learned a little more about a multimeter. I'll bet the starting is still rough this morning, but I may just have to live with it for now.

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1982 300cd, 140k miles

Use the same polarity as if they were installed (+) to the Termnal end where the wire attaches and (-) to the Threaded Body end (but do not touch the Battery Terminal to the Tip itself).
As for length of time; just think of how long your Glow Plug light is on and even go 20 seconds past that; is safe.
They should get red to yellow red.

You might just get some Bosch Glow Plugs just to get the job over with and find out for sure if it is really the Glow Plugs causing the problem.
If the Bosch plugs solve the problem return the Monarks and let the parts company deal with if they work or not (explain the situation to them).

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84 300D, 82 Volvo 244Gl Diesel

your plugs are good.
i have Monarks and they seem fine since i put them in last fall.
i think you have a fuel problem. can you spray some WD40 in the intake to see if it will start on that and thus bleed the air in the fuel system out? looks like the new injectors have air in them.
keep us informed whatever you do.
roberto

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1985 300SD
1998 Jetta TDI
Previous: lots of diesel VW's, MB's, KW's, Pete, Freightliner


Walking isn't a lost art: one must, by some means, get to the garage.

Ross, you never said if you had 12 volts at the glow plugs.


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1984 MB 300SD Turbo

Thanks for the continued suggestions. I have to admit, it rained here today, and I got occupied with some indoor projects, so didn't even go out and crank the car.

Diesel911, I thought about just getting new Bosch plugs yesterday (Saturday) and trying them to see what happened. However, I went ahead and reassembled everything, so am now at one of those junctions where I either tolerate what I have or take it all apart again to replace the plugs. That seems like one of the best tests though.

Roberto, it certainly could be a fuel problem. I have had the "hard lines" off at least 4 times over the last month, between replacing the injectors and then fiddling around with these GPs. While my cold starts are just as rough as when I would first crank after replacing all injector lines, my warm starts and on-the-road running/idle/etc are all pretty smooth. As a trial, I might try your WD40 suggestion though.

Ryan Z, good point. I should have been more clear, but I do think that I have 12 volts at each GP. With GPs out of car, and key in "glow" position/position 2 (?), I got 12 volts at each harness-GP connection (the terminal from the harness that connects to each GP).

Thanks to all of you for your thoughts and time. I will keep you posted. The 5 new Bosch plugs as a trial seems like a potential next step.

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1982 300cd, 140k miles

I just wanted to provide some f/u to this thread that I started.

The car cranks fine with minimal stumble/smoke IF I allow a full glow cycle to occur ("click" heard at GP relay, cabin light brightens). It seems to take about 25 seconds for this to occur, AFTER my glow plug indicator lamp goes out.

Warm starts continue to be no problem, even if I crank before the indicator lamp goes out.

So, I still don't really know if the GPs are inadequate, or if the "thermostat" (that I yet to understand) that tells the indicator lamp when to turn off is just worn-out/inaccurate. I suppose the next test will be to see what happens during the first start of a cold winter morning. Luckily, I'll be moving back to Alabama in a year, so cold winter starts will be a fading problem.

Thanks for the input given above.

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1982 300cd, 140k miles