B7100 Glow plug questions

torch

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B7100HSD, B2789, B2550, B4672, RC54-71B, 48" cultivator, homemade FEL and Cab
Jun 10, 2016
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The last few cold starts have required lots of glow time, even with the block heater plugged in. So I thought I would do some checks. Rear cylinder: over 9v to the plug. Centre cylinder, under 8v to the plug. Front cylinder slightly less again. Sounds like some corrosion on the connections, so I thought I would remove the nuts and clean them.

The nuts are round, with a light knurl and a straight slot offset from the threaded hole. A straight screwdriver loosened the rear one. I cleaned it up and now voltage to the middle one is about 1 volt, so I guess that's where the problem is an I made it worse.

Darned if I can get that middle one loose though. I've used enough force to start distorting the slot. There's not enough room between the plug and the manifold to grab the knurl with pliers or vice-grips. I tried some small needle-nose vice-grips but they just started to slip. Is there a special tool for this job?

While I'm on the subject, what size socket do I need in the event that the plug has to come out?
 

BruceP

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G5200H
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Once you get the wires/connections off of the GPs... you can use an ohmmeter with one lead clipped to the engine-block. With the other probe, touch each of the GPs one at a time. All of them should read approximately the same resistance.

There is no need to remove the ones which match each other. However, any GPs which are open-circuit, need to be replaced.

BTW: The voltages you read may be OK... the GPs draw high current hence, each one will create a voltage-drop down the 'chain'.

An improvement I did to my engine was to connect the incoming wire to the center GP. This reduces the voltage-drop to the other two.
 
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Russell King

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I don’t recall the size but you will need a deep socket with a normal to thin wall.

You may be able to use two small screwdrivers, one on each side and a bar to twist the nut off. Application of penetrating oil may not be a good idea on glow plugs but no real idea if it would cause any problems.
 

Dave_eng

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Torch
I have had great success with difficult screws on motorcycles with the hammer blow impact tool.
Here is a very informative video.

Haggerty

This tool has loosed frail screws in aluminum where a simple twisting action either breaks the screw or strips the head.

The impact tools are not expensive.

Dave
 

torch

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B7100HSD, B2789, B2550, B4672, RC54-71B, 48" cultivator, homemade FEL and Cab
Jun 10, 2016
2,307
541
113
Muskoka, Ont.
Dave,-

I have two of those. Any idea what the effect of hitting the top of a glow plug with a hammer is?
 

torch

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B7100HSD, B2789, B2550, B4672, RC54-71B, 48" cultivator, homemade FEL and Cab
Jun 10, 2016
2,307
541
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Muskoka, Ont.
An improvement I did to my engine was to connect the incoming wire to the center GP. This reduces the voltage-drop to the other two.
Hmmm. Doesn't really help me figure out how to get the wires off in the first place, but does give me an idea: There might be enough thread exposed above the existing nuts to simply add new wires and nuts on top. If I add a short lead to each, I can run them all to the supply wire and abandon the existing aluminium ones.
 

BruceP

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G5200H
Aug 7, 2016
748
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Richmond, Vermont, USA
If I add a short lead to each, I can run them all to the supply wire and abandon the existing aluminium ones.
That is perfectly good way to optimize current supply to the gowplugs. Be sure to use heavy-enough gauge wire to carry the current. Since copper is expensive, you may find this is not a cheep way to improve things.

---------------------------------
If the existing daisy-chain wires are truly ALUMINUM... there is room for improvement.

Aluminum is a pretty good conductor of electricity.... HOWEVER, it is prone to corrosion when connecting to dissimilar metals. This corrosion is an electrical insulator. Infact, when aluminum started to be used in structure-wiring...there were MANY fires due to this aluminum-oxide corrosion.
Using aluminum to wire homes was largely abandond after that.

On my Kubota engine, the daisy-chain of jumpers between glowplugs is COPPER. (far superior to aluminum as reliable electrical conductor) It should be trivial to procure a 6inch length of 10gauge copper house-wiring. (This contains 3 6inch lengths within it). Just strip the insulation and use the copper to fabricate your own daisy-chain.
 
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BruceP

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G5200H
Aug 7, 2016
748
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Richmond, Vermont, USA
Hmmm. Doesn't really help me figure out how to get the wires off
Beware that the GPs (just like spark-plugs) are made out of CERAMIC. Hence, they will shatter like glass. DO NOT use a hammer on them. Treat them as if they are made from glass. Too much force in ANY direction will break them (even if you do not visually SEE the damage)

As others have mentioned, soak with a good penetrant and re-try to loosen the stubborn nut. Start with the least-aggressive... and work your way up to needle-nose vice-grips. Even cutting the nut off with dremel cutoff wheel is an option. (any copper/brass/bronze metric nut should work just fine as replacement.)

If all else fails, you may need to use destructive means to remove and replace the GP.

-------------
Do not forget that by disconnecting the OTHER two GPs, you can use ohmmeter to test the one which remains.

-----------------------------------------------
Another perfectly-good option is to LEAVE IT ALONE. If you are getting a voltage-drop, assume that GP is working.
 
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torch

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B7100HSD, B2789, B2550, B4672, RC54-71B, 48" cultivator, homemade FEL and Cab
Jun 10, 2016
2,307
541
113
Muskoka, Ont.
It was -21° this morning. I plugged in the block heater for 2 hours, installed a jumper with alligator clips from the rear to the centre glow plug, preheated for a minute and she fired up on all 3 with no stumble or white smoke. So I think that supports the corroded connection hypothesis.

For now the jumper will suffice. Did I mention it was -21° out? It's supposed to warm up a bit in a few days -- I'll tackle it then.
 
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Dave_eng

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Dave,-

I have two of those. Any idea what the effect of hitting the top of a glow plug with a hammer is?
Torch
I have not used this tool on a GP before and agree your caution is merited!
I have been thinking of your problem since you first posted.
I would be inclined to buy a set of special glow plug sockets from Amazon and focus on removing the plug after cutting the aluminum conductor. Your local NAPA may have loaners.
With the glow plug in the vice you can see if there is any negative consequence to using the impact driver.

Alternatively, knowing you have great welding skills, a loader build being one example, I would wrap a wet rag around the GP and try using a small oxyacetylene tip to quickly just heat the frozen fastener.

Please post the final chapter as there is learning in it for everyone.

Dave
 

Dave_eng

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Are there any special considerations when using acetylene as opposed to propane, MAPP, or natural gas?
My goal in these situations is speed. You want to quickly heat the nut and nothing else around it to make the most from different coefficients of expansion.

The gases which are being burned without concentrated oxygen being introduced into the flame take longer to raise a component's temperature and as a consequence more surrounding parts are warmed too.

Dave
 

torch

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Equipment
B7100HSD, B2789, B2550, B4672, RC54-71B, 48" cultivator, homemade FEL and Cab
Jun 10, 2016
2,307
541
113
Muskoka, Ont.
My goal in these situations is speed. You want to quickly heat the nut and nothing else around it to make the most from different coefficients of expansion.
I have an acetylene torch. I also have an inductive heater that I purchased around a year ago and am really learning to like. It heats nuts very quickly without waving a flame around. Very useful in many situations. Two weeks ago I used it to heat the nuts on a gas tank sender unit attached to a plastic gas tank. I wouldn't have dared try that with the torch!
 

Dave_eng

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M7040, Nuffield 465
Oct 6, 2012
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Williamstown Ontario Canada
I have an acetylene torch. I also have an inductive heater that I purchased around a year ago and am really learning to like. It heats nuts very quickly without waving a flame around. Very useful in many situations. Two weeks ago I used it to heat the nuts on a gas tank sender unit attached to a plastic gas tank. I wouldn't have dared try that with the torch!
It has been my goal to get an inductive heater........ best tool for your GP nut

Dave