Glow plug problem ?

[dvorocks]

I have a 1990 aprox 3cylinder kubota generator in my motorhome... It starts really rough if at all..Once started runs great
Today being cold and rainy it wouldnt start...I tested the glow plugs..
My test ( not sure if im doing it right)
Turn glow plugs on and the first glow plug read 9 volts and the rest of them didnt have and power.. My guess is a bad ground? I have had previous ground related issues on this motorhome..
Shouldnt all 3 plugs read the same? Any help would be great

 

[birddogger]

They ground to the cylinder head like spark-plugs; if they didn't have ground the voltage should still be at the terminal. My first thought is the jumper from the first plug to the second is broken or loose. The tiny nuts that hold the jumpers never are very tight and it wouldn't take must to vibrate loose. Mine are round with a small slot in them, put a fine screwdriver in the slot and make sure they are tightened firmly but DO NOT twist crazy hard, like finger tight and 1/8 turn. You could twirl the heating wire in the plug and then they are shot.
Or, disconnect the wires, DO NOT drop the nuts, they are metric of course. Then measure the DC resistance of each glow-plug with an ohm-meter; they should be under 5 ohms, usually close to 1 ohm.

 

[dvorocks]

Thanks for the reply...I tightened the jumper wire nuts...Thought it was that for sure because they were pretty loose.. No such luck... I really dont understand how there could be power at the first glowplug and not at the next 2? All there is is a wire to connect the 3..
I tried to test with my multi meter for ohms...Never did that before
I put the meter on ohms put the ground jumper onthe engines ground and then on each glow plug..Not sure i was doing it correcting since i didnt get the meter to read anything consistent..

 

[birddogger]

All there is is a wire to connect the 3..

Yeah, it really is that simple. If there is power to the first one then there is power to the others; unless being loose there is some corrosion build-up and the wires and washers are too dirty to connect, even now that you tightened them. You can try carefully disconnecting them, again do not drop a nut; gently brighten up the jumper wires and washers with some emory cloth. Even a scrape with the blade of a knife, just so there's bright metal to make contact.

A second thought occurred, if this has a glow-plug timer; perhaps by the time you move to measure the second plug the timer has shut off and now the power really is zero. If it has a "preheat" position on the switch or button then this is not a concern.

 

[dvorocks]

Ok I will try that... I read somewhere else that puting a my test light negative
on the positive side of battery and then test each glowplug with the positve...Each glow plug worked that way..seems so simple lol

 

[dvorocks]

Problem solved...Your first thought was the right one.. I took everything apart and really cleaned it good...Its amazing what a piece of sand paper can do...You were right those darn little nuts are a pain in the but when you take them off.......Very happy to get that little genny genny going....Thanks again!!!!

 

[dieseldude]

When cleaning the corrosion the connecting wire to each plug, I use The redish brown scotch brite pad or very fine sandpaper when emery paper is no where to be found. It cleans well but not and seems not to deeply score the metal.

The way I test for bad glow plugs is I use a test light or any 12 volt bulb with wire leads. First I remove the connecting wire to all the plugs so all that is seen is the terminal threads. next I clip the ground lead of the test light to the positive (+) battery terminal. Next touch the tip of the test light to the terminal of each plug. A bright light means the plug is probably good. A dim light could be corrosion or a dirty connection. I do it this way so I don't have to wonder if a timer shut off or if a switch is in pre-heat position

That just my 2 cents worth

 

[skeets]

Some thing I learned the hard way was when you make connection or clean one up is to put a dab of like a white lithem grease or a silicon grease on them befor tightening them down,, works really good on head light conectors

 

[Stubbyie]

Silicone grease is the way to go. Stands higher temps (glow plugs / engine) than oil-base greases without melting.

Every light bulb and socket and wiring termination gets a dab.

Virtually all retail silicone grease is chemistry lab 'stopcock' grease repackaged. I get the stuff at wholesale plumbing supply houses in a little container (maybe a tablespoon of grease) for a buck. Plumbers use it as 'stem lube'. NAPA sometimes sells it in small tubes as a major brand 'bulb grease' for some outlandish price.

Don't get silicone grease on anything you'll need to paint in your lifetime. You'll get unbelievable fish-eyes. It can be cleaned from surfaces but you'll need a specific cleaner from an auto paint supply house. Spray-on gasket remover can work but might ding the originally painted surface.

Shot a load of herbicide once on a windy day. Had silicone defoamer in it. Neighbor a mile away (literally) was painting a truck in his barn. He never could figure out why that job went so bad so fast.