Glow Plugs

[Trains1938]

Hi, How do you test the glow plugs in a 254 Jinma tractor? Mine is hard starting and I don't know if the glow plugs are working. When I put the start switch in the heat position the amp meter does not move. Checked the fuse and it seems to be ok.

 

[CobyRupert]

If you want to leave them in place, you could test them with a continuity tester, or more accurately with an ohm meter.
If you figure your battery voltage (“V”) is 12.6 volts, and you measure the resistance (“R”) in ohms, the heat the plug generates is V^2/R, or 12.6^2/R, or 158.8/R (Watts).
So if you measure R as .5 Ohms, it should produce 318 watts of heat.

 

[piper184]

If your amp meter works properly otherwise that is a pretty good indication that your glow plugs are not working. The big question is why?
I would start by putting a volt meter on the bus bar that connects the glow plugs and check for battery voltage when you hit the Heat switch.
If you see battery voltage at the bar, all the circuits are good and most likely all the glow plugs are burned out. If you don't get battery voltage you have to work your way back along the circuit to find the problem.

You can check the resistance of each glow plug but you have to remove the buss bar and do it on each plug individually. I thought I had a listing of what resistance to expect but can't find it. In any case, if you have an open circuit between the tip of the plug and ground, the plug is bad.

 

[Trains1938]

If your amp meter works properly otherwise that is a pretty good indication that your glow plugs are not working. The big question is why?
I would start by putting a volt meter on the bus bar that connects the glow plugs and check for battery voltage when you hit the Heat switch.
If you see battery voltage at the bar, all the circuits are good and most likely all the glow plugs are burned out. If you don't get battery voltage you have to work your way back along the circuit to find the problem.

You can check the resistance of each glow plug but you have to remove the buss bar and do it on each plug individually. I thought I had a listing of what resistance to expect but can't find it. In any case, if you have an open circuit between the tip of the plug and ground, the plug is bad.

 

[Trains1938]

Hi, piper checked the voltage at the bus bar. I am getting 12.4 volts. So what do think? Are they hard to pull out? It is hard to think that all 3 of them go bad at the same time.

 

[Trains1938]

I'd think you could test them with a volt meter, too, or a light. Just connect volt meter or light to top of glow plug and other side to ground. Turn to glow position with ignition switch and see if you get voltage or light on.

 

[Trains1938]

Hi Ralph, this method only confirms power to them, not if they are working. I tested the voltage to them and I am getting 12.4 volts.

 

[CobyRupert]

 

[RalphVa]

Hi Ralph, this method only confirms power to them, not if they are working. I tested the voltage to them and I am getting 12.4 volts.

I realized my mistake and deleted it.

 

[bearthebruce]

So you have voltage to all three? You are assuming the voltage on the bus bar is connecting to the glow plugs? Shouldn't you verify that?

Did you measure each glow plugs resistance? Do you see a resistance on your meter.. probably takes a pretty good meter as these will be relatively low value resistance - as in an ohm or less.

If the resistance is where it ought to be, and the voltage is reaching the plug, then the only other possibility is the ground circuit. One would assume the block of the engine has been connected to the negative terminal of the battery. But, I have been in China and seen some of their wiring!!!! Assume nothing.