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  #16  
Old 12-04-2005, 04:16 PM
BodhiBenz1987's Avatar
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Location: East Coast
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Quote:
Originally Posted by whunter
Glow plug testing.
Glow Plug Testing?

Don't always trust your glow plug indicator light!
Don't always trust your glow plug indicator light!

Glow Plug Relay
Glow Plug Relay

New Glow Plug kit installation. 1978 240D
New Glow Plug kit installation.

Glow plugs link thread
http://www.peachparts.com/shopforum/diesel-discussion/137732-glow-plugs-link-thread.html#post1019018

Replacing Glow Plugs
http://mbdieseldiy.tripod.com/glowplugs.htm
Thanks so much whunter ... I try to do searches but never come up with what I'm looking for ... your quick links are VERY helpful!

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2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
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  #17  
Old 12-04-2005, 04:31 PM
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My car has somewhat of a similar issue. Upon startup (after waiting for glow plug relay to click) the engine shakes pretty hard and then kicks a few times and then smooths out. The idle upon startup is very close to 500 and then after warmed up completley it idles close to 800. I know I still have an air leak somewhere as there are those little tiny bubbles in the prefilter that build up after the engine has warmed up a bit (but dissapear after shutoff and cool down). I am ordering a new rack dampener pin and hopefully that will help. Then after the snow goes away in the spring Ill really get in there and start evaluating my fuel lines.
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  #18  
Old 12-04-2005, 05:07 PM
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Quote:
Originally Posted by Brian Carlton
It is first necessary to verify if the condition is "typical 603" cold starting behavior or whether there is a real problem.

So, next time you have a real cold start (35°F or less) and it has been sitting overnight, turn the key to the #2 position and let the glow plugs light up and remain lit for 35 seconds. Use a watch.

Then start it.

If it runs perfectly smooth, then the behavior is "typical 603" cold starting behavior and you simply need to run the glow plugs longer.

If it kicks and bangs like it did previously and then runs smooth, then you likely have one or two weak, or bad, glow plugs. You can test this, yourself, if you have a meter that measures resistance.

Brian I have read before that you recommend leaving the starting operation for maybe 20/30 seconds. But my brother who is a lincensed mechanic, specialising in heavy-duty diesel trucks all his working life says that the glow plugs, if they are working properly, within a few seconds heat to white hot and then diminish as seconds tick away.

Just curious - What do you say to that?
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  #19  
Old 12-04-2005, 05:14 PM
t walgamuth's Avatar
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Location: Lafayette Indiana
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i dont have

a rebuttal for the brother.

but after reading brians suggestion i have been glowing extra on cold startup. just five extra seconds has made a big difference in my 603.

tom w
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  #20  
Old 12-04-2005, 05:29 PM
dieseldiehard's Avatar
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Well, I know zero abut the glow plugs used in heavy trucks but I dispute the idea that the ones used in Mercedes heat to white hot.
I believe cherry red is more like it, I am sure there are some here that have connected them up and witnessed them heat out of the engine.
I deal with vacuum electronics and can assure you that white hot is impossible in atmosphere because metals oxidize at those temperatures almost instantly. White hot requires a temp in excess of 1050 Degrees C.
The only glow plugs that I know if that operate close to that temp are tiny ones on model airplanes. and they heat in few seconds because of their tiny mass. The heavy walls in the pencil type MB GP's take a while to reach cherry red due to their mass and that is one reason for the timer.

As for the time that they receive current, that depends on the glow plug timer in the relay box, it allows some to operate for 45 seconds (there is the purple wire mod that makes them heat longer too) but different engines (617 in particular) have shorter or loner times programmed in them.
And if the block temp is high enough the timer is bypassed to prevent heating the glow plugs at all, again this depends on the particular model. Some 617 however do not have a block temp sensor so as always, it depends on the car. I'm fairly certain the 603 does sense block temp and the GPO timer drops out after the engine is hot.
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  #21  
Old 12-04-2005, 06:07 PM
Craig
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FWIW, I "bench tested" 4 GPs from my 240D this morning. I don't know if they were quite "white hot" but they were a lot closer to white than "cherry red". Within about 5 seconds the tips were very bright yellow. It took about 5 more seconds for the remainder on the GP "shaft" to reach that color. They continued to glow for at least 30 seconds after I removed the power. I don't know what specific temperature corresponds to that color, but they get a bit hotter than cherry red.
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  #22  
Old 12-04-2005, 06:20 PM
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Quote:
Originally Posted by Padraig
Brian I have read before that you recommend leaving the starting operation for maybe 20/30 seconds. But my brother who is a lincensed mechanic, specialising in heavy-duty diesel trucks all his working life says that the glow plugs, if they are working properly, within a few seconds heat to white hot and then diminish as seconds tick away.

Just curious - What do you say to that?
You'll need to ask your brother why he thinks that the plugs drop temperature after a few seconds. The hotter the plug gets, the less the current flow. Therefore, the plug temperature is self-limiting. It will reach a steady state where the resistance in the plug will provide a specific plug temperature. If the glow plug is cooler than this temperature, the current will be higher and the plug will heat up. If the plug, somehow, was above this temperature, the current will be lower and the plug will cool. The plug will, therefore, remain at the equilibrium temperature for the remaining time available from the relay.

BTW, I don't automatically recommend leaving the plugs on for an extended period. I've found that the 603 benefits from additional glow time, especially when it has been sitting for awhile. The 617 doesn't seem to be anywhere near as sensitive. In fact, I can start the 617 when the light goes out and it will run perfectly smooth at temperatures down to 30°F. I have not tried it at lower temps. as of yet, with the new valves and proper IP timing.
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  #23  
Old 12-04-2005, 06:30 PM
t walgamuth's Avatar
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i agree

the 616 617 doesnt normally need the extra time.

tom w
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..I also have a 427 Cobra replica with an aluminum chassis.
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  #24  
Old 12-04-2005, 07:04 PM
dieseldiehard's Avatar
Dieseldiehard
 
Join Date: Oct 2002
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Quote:
Originally Posted by Craig
FWIW, I "bench tested" 4 GPs from my 240D this morning. I don't know if they were quite "white hot" but they were a lot closer to white than "cherry red". Within about 5 seconds the tips were very bright yellow. It took about 5 more seconds for the remainder on the GP "shaft" to reach that color. They continued to glow for at least 30 seconds after I removed the power. I don't know what specific temperature corresponds to that color, but they get a bit hotter than cherry red.
OK thanks, I learned something!
I found a temperature chart, it says 1900 F is bright yellow. white hot is 2800 F! http://www.banksengineering.com/Refrac_Temp_vs_Color_Chart.jpg
Attached Thumbnails
Shake n' shudder on cold startup ... normal? Worrisome?-refrac_temp_vs_color_chart.jpg  
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  #25  
Old 12-04-2005, 07:11 PM
Craig
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Quote:
Originally Posted by dieseldiehard
OK thanks, I learned something!
I found a temperature chart, it says 1900 F is bright yellow. white hot is 2800 F! http://www.banksengineering.com/Refrac_Temp_vs_Color_Chart.jpg
I would say that they were in the 1900F range based on that chart (just an estimate).
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  #26  
Old 12-04-2005, 07:33 PM
Hatterasguy's Avatar
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Location: Milford, CT
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Quote:
Originally Posted by Padraig
Brian I have read before that you recommend leaving the starting operation for maybe 20/30 seconds. But my brother who is a lincensed mechanic, specialising in heavy-duty diesel trucks all his working life says that the glow plugs, if they are working properly, within a few seconds heat to white hot and then diminish as seconds tick away.

Just curious - What do you say to that?
I'd say your brother doesn't know much about 603's. These are not CAT's or 6-71's. The plugs will continue to glow red until you hear the click which is about 30 seconds on these cars. If you wait longer the pre chamber's will heat up more and give you a smoother start.

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