glow plug theory
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Freshman User
Joined: Feb 2013
Posts: 46
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From: Haines, AK
glow plug theory
I might not ask this question, but you guys always nail these issues dead-on. So here goes:
I just changed glow plugs with good success. I looked them over and found a plug - whitish on the end, seeming to indicate failure at least on that plug. Most of them were all black and sooty. (sorry, no time for a pic)
Black and sooty seemed strange, since they're supposed to be in upstream of the fuel/air mixture injection. How would they get sooty? Or am I missing something?
I just changed glow plugs with good success. I looked them over and found a plug - whitish on the end, seeming to indicate failure at least on that plug. Most of them were all black and sooty. (sorry, no time for a pic)
Black and sooty seemed strange, since they're supposed to be in upstream of the fuel/air mixture injection. How would they get sooty? Or am I missing something?
Posting Guru
Joined: Oct 2011
Posts: 1,647
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From: Exton, PA
i'm pretty darn sure they're in the cylinder itself, i.e. subjected to combustion all the time, not behind a valve or something. ...otherwise how would they help it fire when cold?
like, when you pull the glowplug, if you drop something down the hole it came out of, it goes right into the cylinder!
that said, they shouldn't be too sooty, or it means that your engine may be running too rich, too often. do you have it chipped?
mine were all black on the tips when they came out, but there wasn't any caked soot or anything.
like, when you pull the glowplug, if you drop something down the hole it came out of, it goes right into the cylinder!
that said, they shouldn't be too sooty, or it means that your engine may be running too rich, too often. do you have it chipped?
mine were all black on the tips when they came out, but there wasn't any caked soot or anything.
Lead Driver
Joined: Oct 2003
Posts: 8,476
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From: Madison, WI
Yes, they're right in the chamber; that's how they work (to heat the air and the wall of the chamber). That's also why spraying starting fluid into a diesel engine with working glow plugs can make it go boom.
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Freshman User
Joined: Feb 2013
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From: Haines, AK
Wow. I guess it's right near the valves. I'll make sure and not drop anything down the hole.
I can suppose why mine are dark with soot - my vehicle makes many short trips to town - 5 miles or less - mostly idling. It seems to take about 10 miles to stop its little "cold" shake and get down to business.
I wonder if there's any way to help it make shorter trips. I already have a battery boost plug-in so I don't use as much battery on the cold starts. What is chipping and what would it do?
I can suppose why mine are dark with soot - my vehicle makes many short trips to town - 5 miles or less - mostly idling. It seems to take about 10 miles to stop its little "cold" shake and get down to business.
I wonder if there's any way to help it make shorter trips. I already have a battery boost plug-in so I don't use as much battery on the cold starts. What is chipping and what would it do?
Elder User
Joined: Jan 2012
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From: Southern West Virginia
I'm in the same boat as you - I only live about 3.5 miles away from my work, so I make a lot of short trips. I'll take the car most of the time though.
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Cargo Master
Joined: Feb 2009
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From: Yreka, CA
I only plug my truck in for an hour because of something I read in the 6.0l section. Supposedly in the first hour the coolant gets up too 100*. Dont know if this applies to the 7.3 but an hour always seems like enough for me
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Elder User
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From: Southern West Virginia
It seems I read on here somewhere that it takes several hours for the block heater to get everything up to full temp (not sure what temp that really is), but I suppose there are many variables (i.e. how good your block heater works, ambient air temp, etc). An hour might be just fine. It is certainly better than nothing. I don't have any gauges, so I don't have anything to judge temperature from. I know some have tested this with their trucks.
Cargo Master
Joined: Feb 2009
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From: Yreka, CA
Likewise. If I remember correctly the guy in the 6.0l section said in the first hour his gauge was reading 100*. Then it took 3 more hours to get it up to 200*. So the first hour was the "bang for your buck" period. But it would take someone with a legit coolant gauge to clarify this for a 7.3l...
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Freshman User
Joined: Feb 2013
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From: Haines, AK
I find that if the temps are below 10 degrees I need three hours' heating time to have a respectable startup, and in the last 30 mins I turn on the 500W oil pan heater.
So I understand that the sooty residue on the glow plugs is unburnt diesel within the cylinder from low efficiency (cold engine), and longer runs or a warmer startup condition should be the best solution?
So I understand that the sooty residue on the glow plugs is unburnt diesel within the cylinder from low efficiency (cold engine), and longer runs or a warmer startup condition should be the best solution?
Posting Guru
Joined: Aug 2004
Posts: 2,417
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From: Braham MN
You need to drive that truck ALOT MORE.... those short 5 miles trips and idling all the time are going to ruin your engine, buy a gasser for the short trips.
The one GP that was white was prolly the only one working properly. Black sooty crap on the end tells me your internal combustion temps are no where near hot enough to properly burn the diesel. If the tip of the GP looks like that imagine what your valves and piston bowls look like. take that thing out and run the heck out of it for a good hour, get it hot and make it work.
Diesel Rod
The one GP that was white was prolly the only one working properly. Black sooty crap on the end tells me your internal combustion temps are no where near hot enough to properly burn the diesel. If the tip of the GP looks like that imagine what your valves and piston bowls look like. take that thing out and run the heck out of it for a good hour, get it hot and make it work.
Diesel Rod
Cargo Master
Joined: Feb 2009
Posts: 2,111
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From: Yreka, CA
Scott, didnt you just deal with a bad GPR? That could be a contributor to the buildup I would think. With as cold as it is up there and your GP's not staying lit long enough, or at all, I could understand some buildup.
Hotshot
Joined: Dec 2005
Posts: 14,377
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From: evansville in
The dark tips are from not getting hot enough. Weather it be from gp relay bad,uvch plugs,pigtails low temps or what ever. and yes the pgs are directly in the cyl. I can post up a pic of a head inside so you can see location.