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Old 08-12-2012, 12:50 AM
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Join Date: Mar 2010
Location: Freehold, NJ
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using stock glow plugs to heat oil?

I've read up and still confused about how it all works. If I bypass the stock relay on my 1980 300TD and I get the kit that allows me to control the timer for the glowplugs, will it heat the wvo in the engine or not. I would think that If I had the stock glow plugs heat while my newly installed heater also heated the oil before the engine, it would start easier? please educate me on this and let me know if this would work.

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Old 08-12-2012, 08:25 AM
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Posts: 18,355
No. Glowplugs don't heat the fuel.
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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Old 08-12-2012, 09:04 PM
Join Date: Jun 2012
Location: Virginia
Posts: 790
glow plugs are only really used in cold weather, and even then, are only turned on for a few minutes (at most). they heat the air in the combustion chamber, so that it's hot enough to ignite the fuel when the fuel gets injected.

gasoline will ignite as low as -30 F. diesel fuel on the other hand, won't ignite until it's several hundred degrees F. a very large difference. normally the high compression ratio of a diesel engine heats the air sufficiently for combustion to occur. when its cold out however, the glow plugs assist by putting some more heat into the air in the combustion chamber.

glow plugs do not heat the fuel. they do not heat the oil either. they heat the air. if you put a hot glow plug into fuel or oil, you'll start a fire. glow plugs get extremely hot!
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Old 08-18-2012, 08:34 AM
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once a happy man
Join Date: Nov 2008
Location: bristol,tn
Posts: 5,825
you can make a glow plug heater by using a cheaper glow plugs and a pipe to drill glow holes.Then reduce pipe to 7/16s.But you need to run filter after it as tiny bits of carbon can mess up a IP
I use fatty wagons injector line heaters,to make sure my oil is over 180 degrees.I haven't run my emergency fuel for over a year and a half.storing it in case of war
plant, and animal life matter. human's had their chance.

Last edited by oldsinner111; 08-18-2012 at 10:11 AM.
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Old 08-18-2012, 10:11 AM
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Location: 2021 - The Great Florida Count-down
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A 30 plate HE (or bigger) is really one option that should be seriously considered on top of a 2 tank system, e.g., starting and ending on #2. Fattywagons makes a nice product and Kieran stands behind his product. When burning WVO, the better systems use a lot of gizmo's to heat the grease to the optimal 180 F, but one must generally always start the engine when cold which generally means the WVO will be cold too. A couple of minutes on #2 then warmed up WVO and a purge about 20 seconds before you turn it off really ensures the cleanest environment (on top of purified WVO). My .02 cents.
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Old 08-19-2012, 09:15 PM
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Join Date: Apr 2010
Location: West Quebec
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A whole bunch of folks answered this question for you in the main diesel forum. The forum moderator even posted a cutaway drawing of where the glow plug sits....

1980 w123 glow plug wiring

The issue here is that the WVO has to be heated BEFORE it reaches the injection pump and maximum heat has to be achieved before it reaches the injector.

Otherwise you are pushing thick sludge through a precision instrument (the pump) that is designed to push diesel fuel -- and doing the equivalent of sucking bacon fat through a soft drink straw in passing it through the injector. Trying to add heat by means of the glow plug AFTER all that has occurred is next to useless.

ADDITION: Okay now I think I see where you may be going here... I came across your earlier posting about dumping in the WVO before you installed a kit, etc. Are you simply trying to get the car started? If so you should just ask about that.

2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Last edited by Zacharias; 08-20-2012 at 09:19 PM.
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Old 09-04-2012, 01:18 AM
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Join Date: Mar 2010
Location: Freehold, NJ
Posts: 490
Sorry for not replying. I have it working now. What I didn't understand originally was where the detonation occurred in the engine. I figured the glow plugs were where they are do heat the diesel up when its cold so I figured that it would be logical to assume that it would heat the WVO in that area too. I guess that's not the case. Since I posted this I did install a separate small underhood tank to put diesel fuel in so before I shut the car off I switch it to run on diesel for about 30 seconds and she fires right back up when cold on diesel. Then I switch it back over to WVO after she's been running a min or so. I have a heater set up to heat the WVO now before it enters the injection pump. I'm currently running it on about 80% wvo and 20% diesel and she purrs like a kitten. When diesel only is in it she has the usual clank sound at idle. When I switch it over it smooths right out in about 30 seconds or so. Hopefully this clears up what I was trying to explain when I started the post. Any other advice? Especially for when it starts getting cooler? Thanks again.

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