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Old 06-09-2009, 06:22 PM   #1
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Default Glow Plug Problems

I am running a OS.21vg in my son's rc8, it has been a great little motor for him. It has about 1/2 gal. of fuel in now. We will run a 7min. qual. and shut the motor off at the end of the run, when we go to crank it for the next qual. or main the glow plug is shot. The engine runs @ 230deg. and idles & runs fine. The needle settings seem spot on. Any thoughts would be great, Thanks
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Old 06-09-2009, 07:53 PM   #2
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what does the plug look liek when you take it out, is the wire deformed? what are the temp and the end of the run? you can have a motor that seems to run great but be lean on the low speed needle or the opposit being to lean on the high side.
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Old 06-10-2009, 06:24 AM   #3
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The plug color is fine the wire is deformed (pulled into the plug), engine temps are 220 to 230 deg. w/ good smoke coming from pipe. Would a lean bottom needle cause this?
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Old 06-10-2009, 08:05 AM   #4
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its very possible, when you pinch the fuel line about an inch from the carb it should take approx 3 sec for the idle to increase, it if take longer its too rich, if it take less time its too lean. once you pinch the fuel line it should just start to rise in rpm at 3 sec.
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Old 06-10-2009, 08:55 AM   #5
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i had a similar problem in a much lesser motor that an os a few years ago and what the problem was, was the compression was to high, so i added a .010 shim and never had a problem after that...plus what plugs/nitro % are ya running...
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Old 06-10-2009, 01:03 PM   #6
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Mudboger, I have the car cleaned up and ready to run again for friday night i'll do a pinch test tomorrow. Thanks. Hustler777 I am running mc59 w/ 30% Byrons, it also ate a OS plug. Thanks.
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Old 06-10-2009, 05:24 PM   #7
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Check for air leaks.
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Old 06-10-2009, 08:38 PM   #8
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check for air leaks and richen up the bottom end a hour or two like others have posted previously....if that doesnt help, id look into the head shimming....but check the other problems first, only dig into the motor if the problem isnt fixed by anything else.....what color is the glow plug when u pull it out? if it looks like new and wet with fuel ur pretty rich. if its lightly brow and the wire is grey in color but not distorted and its dry ur pretty close to optimum. if its dark brown/black and the wire is burnt and distorted, ur way lean....hope this helps, it can be kinda agrivating at times lol
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Old 06-10-2009, 10:55 PM   #9
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before you get crazy with adjusting conpression, try running a little cooler plug. If you are running a hotter plug, the filiment is very thin and will distort if your tune is close to perfect and/or the compression is border line. The hotter plugs will tend to detonate and distort the filiment and ruin the plug. By running a cooler plug, it delays ignition enough to reduce or eliminate preignition, lowers combustion temps and will allow a greater window of tune. The hot plugs have to be spot on with the tune or you run the risk of overly rich flame outs or preignition if the tune changes as the day progresses. If the engine is shimmed to stock specs, that should do the trick provided all other elements are intact.
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Old 06-11-2009, 04:25 PM   #10
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Quote:
Originally Posted by PowerHouse View Post
before you get crazy with adjusting conpression, try running a little cooler plug. If you are running a hotter plug, the filiment is very thin and will distort if your tune is close to perfect and/or the compression is border line. The hotter plugs will tend to detonate and distort the filiment and ruin the plug. By running a cooler plug, it delays ignition enough to reduce or eliminate preignition, lowers combustion temps and will allow a greater window of tune. The hot plugs have to be spot on with the tune or you run the risk of overly rich flame outs or preignition if the tune changes as the day progresses. If the engine is shimmed to stock specs, that should do the trick provided all other elements are intact.
This advice is sound, you're running a 59 which is a hot plug with 30% nitro. Here is the OS Glow plug chart for reference or try steeping down and use a MC8.

osengines.com/accys/glowplugs.html
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