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  #1  
Old 12-02-2011, 03:50 PM
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One bad glow plug--no start

Cold here this morning, probably in the teens or single digits. Daughter's SD didn't start. After she tried, I tried and quickly gave up. Now that it's warmed up I checked the glow plugs. #4 was completely open.
Here's the interesting part: when I tried to start it, it would give a couple of strong revolutions, then almost come to a stop, then a couple of strong revolutions again and then almost stopping again. Here's my hypothesis about what was happening; #4 cylinder had no heat at all. Diesel fuel was accumulating in that cylinder and the engine was compressing it, making that compression stroke much harder than the rest. Does anyone have another hypothesis? If I'm right, it explains why a single completely bad plug will stop a 617 from starting. It stops the engine from building up high rpm's thru a continued sequence of engine revolutions, only turning the engine in short bursts of speed.
It should be cold again in the morning so I can see how it performs with a new plug.

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  #2  
Old 12-02-2011, 05:41 PM
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Sounds plausible. I've always had to have at least two bad ones to get hard starting, but I don't usually have to start my car in temperatures as cold as you're dealing with.
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  #3  
Old 12-02-2011, 06:28 PM
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On a new 617 it may take 2 bad GP's to prevent starting. With a motor with 300k + miles on it 1 plug maybe enough. I know with my high mileage 617 if the all the GP's were not spot on & the battery perfect, it wouldnt start on cold mornings (~ 20F) if it had been left out in the cold over night. Having valves right on their limit of tightness (gap) would also not help. I have used a hair dryer to give it a dose of warm air. It works!
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1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
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  #4  
Old 12-02-2011, 06:34 PM
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Motor has about 30k on it either from new or a rebuild, not sure which.
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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
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  #5  
Old 12-02-2011, 06:36 PM
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Single digits is difficult, although my guess is that the SD would start on four. I haven't attempted it.

I can say, with assurance, that it will easily start on four if the temperature climbs into the '20s.

The two other variables are compression and cranking speed. Reduce compression a bit on an engine with original valves and have an old starter and/or and old battery and you're in a completely different ballpark. Under this situation, you absolutely need all five to start in the single digits.

I recall the SD prior to the reconditioned head. It was touch and go to start with all five in the single digits. 15 seconds of cranking was necessary.


So, no real conclusions can be made because the individual variables are much larger than the four or five plugs.
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  #6  
Old 12-02-2011, 06:42 PM
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I'm not sure what the first attempt cranking speed was since my daughter had tried to start it three times before giving up. She did describe the same behavior I witnessed when I tried it the 4th time. Good rpm, slow down, good rpm again. Maybe the battery is weak. No prior evidence of a poor battery. I'll see tomorrow morning
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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
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  #7  
Old 12-02-2011, 06:50 PM
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Quote:
Originally Posted by kerry View Post
I'm not sure what the first attempt cranking speed was since my daughter had tried to start it three times before giving up. She did describe the same behavior I witnessed when I tried it the 4th time. Good rpm, slow down, good rpm again. Maybe the battery is weak. No prior evidence of a poor battery. I'll see tomorrow morning
I do recall the dark days of the SD.

If you cranked it without opening the rack (contrary to procedure), you would get a specific cranking speed. However, once you opened the rack fully, the cranking speed would absolutely slow down and your hopes of starting were seriously diminished.

So, you definitely have something to support the theory that cold, liquid fuel reduces the capability to crank.

Whether a new battery will easily overcome this would be my question.
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  #8  
Old 12-02-2011, 08:32 PM
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how do you KNOW only one plug is bad?
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  #9  
Old 12-02-2011, 08:44 PM
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Somewhere on the internet is a chart that shows what happens to Battery performance when explsed to the Cold.
A several year old Battery might not work well in the Cold.

You did not mention your Daughter preglowed to the max amount that the Relay and Glow Plugs would stay on; about 30 seconds or did She just use the Glow Plug Light as a guide?

Also a few members have claimed that after the Reamed out the Carbon from the Glow Plug Holes they got easier starting.
If you did that you could also check all of the Glow Plugs over the Battery to see if they heat up properly; from the tip back.

In the Pic below the no good Glow Plug is not getting hot at the tip where it is supposed to (it is a Monark Glow plug).
However, the Plug checked out OK with the Ohm Meter.
Attached Thumbnails
One bad glow plug--no start-glow-plug-test-ngb.jpg  
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  #10  
Old 12-02-2011, 09:35 PM
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that is a great picture. imagine the plug is in a chamber of carbon from lack of reaming, and only the tip is inside the prechamber... fuel is going to spray on the tip, and turn into a warmed mist... not instantly vaporize and ignite...

so, Kerry, did you only ohm the plugs, or did you actually pull them, and found only one not working?
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #11  
Old 12-02-2011, 09:57 PM
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I only ohmed them out. There could be more than one bad. Only #4 was completely open. There are a couple of others that are less than 9 months old. It had one weak plug last winter and started when cold but didn't run smoothly once it fired up. But in this case one plug wasn't just weak, it was completely inoperable.
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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
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  #12  
Old 12-02-2011, 10:00 PM
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Quote:
Originally Posted by Diesel911 View Post
You did not mention your Daughter preglowed to the max amount that the Relay and Glow Plugs would stay on; about 30 seconds or did She just use the Glow Plug Light as a guide?
.
She was waiting until the light went out and then counting to 15 before energizing the starter.
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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
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  #13  
Old 12-02-2011, 10:43 PM
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I have started mine on 3 plugs when it was about 20f out....coughed/shook a bit but fired right up. There's no way that fuel would accumulate in the cylinder to that level, most is carried back out during the exhaust stroke if any were to build up. Sounds like a weak starter to me. I have started mine with the glow plugs disconnected when it was about 60f out before....cranked for about 7-8 seconds, coughed for about 3-4 more then started, no slowdown in the cranking.
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  #14  
Old 12-03-2011, 07:16 AM
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On the front porch of my house I have two lights. I have discovered that if I replace one bulb the other will go out shortly....within days....so if one goes out I change them both and get it over with.

I treat the glow plugs the same way. When I change glows on the 616 or 617 engines I have to remove the hard lines because of my big hands and lack of patience for tedious access tasks.

So if I have one glow go bad I will generally bite the bullet and spring for all new bosch plugs since I don't want to do it all again for a good long while.

And I don't trust testing them any way except taking a jumper cable and testing the glow right on the battery terminals. If it does not glow immediately or fully it is junk.
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  #15  
Old 12-03-2011, 07:26 AM
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Quote:
Originally Posted by t walgamuth View Post
On the front porch of my house I have two lights. I have discovered that if I replace one bulb the other will go out shortly....within days....so if one goes out I change them both and get it over with.

I treat the glow plugs the same way. When I change glows on the 616 or 617 engines I have to remove the hard lines because of my big hands and lack of patience for tedious access tasks.

So if I have one glow go bad I will generally bite the bullet and spring for all new bosch plugs since I don't want to do it all again for a good long while.

And I don't trust testing them any way except taking a jumper cable and testing the glow right on the battery terminals. If it does not glow immediately or fully it is junk.
X2
On this Tom I agree with you & do the same.
You guys are at the start of winter. Who would want to be having to change out another GP in a months time?
Best give the motor its best chance over the next few months.
GP's & valves should have been taken care of a month ago !!!
If you have a block heater, give it a test as well.

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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving
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