Glowplug test
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Glowplug test
Ok I installed a bypass switch that worked great for about 3 weeks. This morning I tried to start and my bypass switch did not work ( I know this because my clock lights dim when I throw my glowplug switch). What is the correct sequence for checking the glow plugs with a tester, ( key off or on, switch off or on).any thoughts? Thanks 89 F-350 7.3
Fleet Mechanic
Joined: Sep 2005
Posts: 1,509
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From: Ladner, British Columbia
I don't know about the correct way to test glow plug, the practical and simple way to do it is as follows.
1.0 Pull the electrical connector off each plug.
2.0 Connect a standard 12V test light to the +ve terminal on your battery.
3.0 Touch the negative on your battery to test whether the light works.
4.0 Touch the glowplug at the tip were the electrical connector used to connect.
5.0 If the Test light lights up the plug is good.
6.0 If the Test light does not light up or is dim then the plug is bad.
7.0 If you find a bad plug replace them all unless you just replaced them all
8.0 Only replace with Beru/Motorcraft Plug (or maybe "Bosch" Plugs that say "Made in Germany" right on the body of the plug)
1.0 Pull the electrical connector off each plug.
2.0 Connect a standard 12V test light to the +ve terminal on your battery.
3.0 Touch the negative on your battery to test whether the light works.
4.0 Touch the glowplug at the tip were the electrical connector used to connect.
5.0 If the Test light lights up the plug is good.
6.0 If the Test light does not light up or is dim then the plug is bad.
7.0 If you find a bad plug replace them all unless you just replaced them all
8.0 Only replace with Beru/Motorcraft Plug (or maybe "Bosch" Plugs that say "Made in Germany" right on the body of the plug)
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Thanks, Best I can tell I have one out of the 8 that is good. All of them are on very tight, I dont know how much force to use, obviously I dont want to use to much. I'm thinking of seeking professional help. Thanks again
Fleet Mechanic
Joined: Sep 2005
Posts: 1,509
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From: Ladner, British Columbia
It may take a bid of torque to initially start the thread and get the plug turning; however once it moved it should start to turn easier. If it is a fight all the way out then be careful not to break them off.
The fact that you seem to have only one good plug left is disturbing although not suprising as the remaining plugs can burn out a lot faster once one plug has failed and if not attended eventually all plug will go.
Hopefully you don't have any Autolite, Champion, or Lucas brand plugs as all these brands have a tendency to swell up on the tips and can break off as you remove them.
Keep in mind even a professional mechanic might not be able to remove a swollen plug without breaking it and he may have to pull the cylinder heads to get any broken tips removed if all else fails.
Best of luck, lets hope all plugs come out easy and in one piece.
The fact that you seem to have only one good plug left is disturbing although not suprising as the remaining plugs can burn out a lot faster once one plug has failed and if not attended eventually all plug will go.
Hopefully you don't have any Autolite, Champion, or Lucas brand plugs as all these brands have a tendency to swell up on the tips and can break off as you remove them.
Keep in mind even a professional mechanic might not be able to remove a swollen plug without breaking it and he may have to pull the cylinder heads to get any broken tips removed if all else fails.
Best of luck, lets hope all plugs come out easy and in one piece.
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Use lots of PB blaster or somthing like that and take your time getting the diffucult plugs out... I had 5 that were really binding they were coming out--- need to slow down and oil them up.. let them sit / soak and go to another plug. Work them down ..oil... bring them up...oil. and remeber the tips will break easier when there warmed by friction with carbon in the prechamber. I did this and still broke one tip out of 5 really stuck ones ( very neglected motor). Got it out with the vacume method .
