Lately my CD runs a little rough for the first 30 seconds or so after a cold start up. It still starts easily and once it runs a few seconds it smooths right out. So, I'm pretty sure one (or two) of my GPs has probably died. Not that big of a deal since I have some good spares lying around.

My question: what is the quickest, easiest way to pinpoint which one? Any suggestions on how to do it other then disconnecting the wire and checking their resistance one at a time? The weather around here right now doesn't encourage spending much time outside working on cars (cold rain), so I'd really like to minimize the time spent on diagnosis and repair of this relatively minor issue.

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1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

You pull the plug at the relay and check resistance on each socket in the plug. If it takes you more than two minutes........you're doing something wrong.

That sounds great. Where is the relay located, and which socket matches up with which plug? Sorry, I don't have a manual...

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1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

You can put an Amp meter around each wire going to the GP's are see which one is lower than usual.

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It's a black box about twice the size of a cigarette pack and should be on the left fenderwell. There will be a plug with five sockets inside. There are small numbers next to each socket signifying the cylinder number. Look carefully.

Another good idea - if I had one of those amp meters that you clamp around the wire...

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1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

The Diesel Giant site has a pictorial on how to check the Glow Plugs with a meter. When the page opens up you will need to scroll down the page some to see it.

If you do not have a Meter Harbor Freight sells digital Volt/Ohm/Multimeters for $3.

Also the Gloe Plug connector at the Relay has tiny littl numbers that tell you what Cylinder it goes to.

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84 300D, 82 Volvo 244Gl Diesel

No problem there - I have 4 different meters I can use.
Thanks guys. With that info in hand it sounds like it should be a cinch to figure out which one is dead...

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1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

Jut a quick update for those who offered help and suggestions.

I measured all of the plugs at the connector and got 1.9-2 Ohms on all 5 - none burned out. I read in other threads that some people wait until 5-10 seconds after the GP light goes out before cranking, so I tried that and got better results - less stumbling and a smoother idle.

So I decided to try the next step up. I've been cycling the GPs twice lately - as soon as the GP light goes out I turn the ignition off and then immediately back on. Once the light goes out a second time, THEN I crank it over. Works like a charm. Idles normally right off the bat again.

We've been having overnight temps in the low to mid teens for the last couple of weeks so this must be just my CD's way of punishing me for making it sit outside in the cold insead of inside a warm garage somewhere

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1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

Although all those plugs work, they're probably old as hell and are not providing the necessary tip temperature. If you can find a warm day, change all five. Remove the hardlines as a group to save yourself some misery.

We have been getting down in the twenties at night. My 83sd will kick a couple of times if I don't plug it in. So I plug it in. The car is MUCH happier to start when the coolant and block is hot. Don't fool with the glow plug light. That is just going to tell you when two or more plugs are bad. It will tell you that by not coming on at all. The time cycle for the plugs is about 30 seconds. I usually just watch the orange low fuel warning light and when it brightens, that means the plugs are no longer warming. So two cycles should be about a minute.

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77' 300D, "Cartman" SOLD @ 150K (didn't know what I had)
83' 300SD, "The Superdon" 325k+ @ 28mpg
95 E320 wagon, "Millennium Falcon" 231k+ @ 24 Mpg
95 E300D, "Sherley" 308k @ 33.69 Mpg, currently anticipating a head
99 Suzuki Intruder "Trudy" @ 45 mpg

Hi Bob,
When I bench tested my glow plugs, the time it took for the tip to get red hot was about as long as the glow plug light stays on. The longer you let them glow, the hotter it gets in there and the easier it is for the car to run smooth. I let them glow until the relay kicks off, turn the key off and then start her up.

Hey, there's a nice CD in Tacoma right now for $1,000.00

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1981 300TD "The Green Lantern"
1980 300TD
1983 300D Euro "China Cat"

If you don't touch the key the glow plugs will stay on for quite some time after the light goes out, 45 seconds or so. You can hear the relay kick off. When it gets cold wait until the relay kicks off before you start the car or you can turn the key off and go another for another glow round. This will help a ton. The way you are doing it you are getting about 20sec of glow time, two 10 sec glows. It takes a glow plug several seconds to get up to temp, so you aren't getting the most out of your plugs. If you wait until the relay kicks off to start a second glow you are getting 45sec straight, plus whatever time you go the second round. Much warmer, and a much happier cold start.

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Actually I replaced them right after I got the car - about 18 months or so ago...

The 20+ seconds I'm waiting now seems sufficient. Two glow plug "light cycles" and it fired off and ran smooth this morning at 13*. I'll keep the info on longer cycles and the length of the relay timer filed away for future reference.

I can always wait a little longer to crank it if 20 seconds isn't cuttin' it...

__________________
1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

Where? On CL?

__________________
1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown