No "glow" Glow Plugs

[ToolManRick]

No \"glow\" Glow Plugs

Any idea on what might cause all three glow plugs, that have never really been used, to fail?

When I first got my Jinma 204 (Nortrac 204C) it did have an amperage draw when the switch was in that position. And admittedly that is no guarantee that all three were working even back then. I still have voltage at the glow plugs, but they show "open" on the ohm meter. When I get home this evening I'll actually remove them from the engine and give'm a visual check. Just curious as to what may have caused their failure.

Pretty sure Northern Tool will stand by the guarantee. I'll give them a call later on today after I do the visual 12 volt glow check.

Thanks guys.

 

[Harrygoodwrench]

Re: No \"glow\" Glow Plugs

Hmmmm, you say all 3 glow plugs show infinity on Ohmeter. Strange that all 3 would burn out(open).
Question, how long do you keep them energized before starting? 30 seconds sounds like a max time but I could be wrong.
Now the China key switch is designed to only energize the glow plugs in the spring loaded position right before start. I'm thinking maybe(however remote) the switch is keeping the plugs energized when you release to run position. Just a quick test-take a test light, touch it to any glow plug tip and turn key switch and see when the light illuminates(you can use the alligator clip connected to the glow plug tip and the probe end of test light to ground to assist in testing while you are sitting on tractor trying to start, its safer too.) Make sure it goes out when key switch is released to run position. The upgrade Ford switch if you have that keeps the plugs energized while in crank position as well as right before crank. I may be entirely wrong but this check should only take a few minutes.
Keep us informed.

 

[DirtPoor]

Re: No \"glow\" Glow Plugs

I'm new to the Jinma tractors and haven't had any problems with their glow plug circuits, etc.
However, owning a Ford truck with an International diesel, I have spent a small fortune on burned out glow plugs (8 X $20= ouch!!).

My lesson learned (ford diesel) was that the control system 'must' have a current limiting feature or resistor that drops the glow plug voltage to about 8 volts (or something less than battery voltage). The glowplugs are connected in parrellel and when any glow plug burns out, the current is reduced and the voltage increases. The higher the voltage, the quicker the remaining glow plugs will burn out. In my V8 situation, once the 2nd or 3rd plug burns out, the remaining plugs are getting the full 12 volts and will burn out after a couple starts.

Now to the Jinma situation. I don't recommend applying full battery voltage to an individual plug unless you know it can handle it.. A continuity test should tell you if it is good and you don't even need to remove it to do that.. You can do a continuity test on all three plug by just removing the copper buss bar on top of the plug, clipping one test lead to some bare metal on the block and the other to the end of the glow plug.

This whole theory may seem 'half baked' and I have no knowledge of any current limiting feature in the Jinma tractors. However, in my aforementioned Ford diesel experience, I did note that the voltage to the glow plugs, when all plugs were good, was about 8 volts while the circuit was energized. When 2 or 3 glow plugs were burned out or disconnected, the voltage would go up to near battery voltage of 12 volts. The remaining glow plugs would fail in short order.

Finally, glow plugs can only tollerate their designed voltage for short periods of time. My Jinma manual specifies "30 sec. Max"

My experience and opinion, FWIW.

Steve

 

[ToolManRick]

Re: No \"glow\" Glow Plugs

Well, I'm doing some guessing too. Like I said I haven't really had to ever use them, but when I first got the tractor I did used to see the ammeter "trip" as I passed over the H to start it. Actually I have nearly always started it by turning the key counter-clockwise and then to "on" when it fired up. I have done the voltage check thing and the switch is working fine and there is voltage at the glow plug buss strip. I'm going to guess that all of them have never worked and now the working one has failed. As stated, I'll give it a go-over when I get home and keep you posted on what I find. Terrible thing to have to work at a normal job on a Friday when I should be home playing in the woods.

 

[ToolManRick]

Re: No \"glow\" Glow Plugs

Forgot to mention Steve that I did do an ohm meter check but it was on the buss while connected to all three. Didn't have time to take the strip off before having to leave for work, but will do an individual check when I get home.

Oh ya, Harry the switch so far is good and behaves as designed. However, if it starts to act up I'll put on the Ford variety.

Thanks for the input. More testing when I get home.

 

[SPIKER]

Re: No \"glow\" Glow Plugs

the glow plugs pull about 30 amps when all 3 are ON and heating. that amperage goes DOWN to about 25 when they WARM UP now if the switch kept them energized full time they would burn out pretty quick... easy check it to put a volt meter on the bus bar and the engine block to check for 12~14 volts when key is on and when running respectivly. if you get that then there is a wireing problem. Only time it should get voltage is WHEN the KEY is held in the GLOW PLUG ON spot. 2nd spot to the left (run is firts spot to left, glow plugs on 2nd spot and key start is 3rd spot.) the JINMA switch does not energize the glow plugs WHEN CRANKING. the FORD REPLACEMENT has same set up but the 3rd spot is GLOW PLUGS ON and CRANKING at same time...

Mark M

 

[greg_g]

Re: No \"glow\" Glow Plugs

The Jinma ignition switch is a piece of crap. Especially since you indicated a habit to turn the switch to the left before starting, I'd say the wafers in that OE switch are shot. I was stupid enough to get a warranty replacement switch, only to have IT fall apart within weeks as well.

The archaic glow plug design used by Jinma belongs to an almost indestructible device. A flakey ignition switch kept mine "glowing" constantly. Yet - after a good cleaning - they worked just fine after replacing that junk switch.

If you DO remove them, watch carefully for the tiny little copper seating washers. If one stays in the block, you should try to get it out before reinstalling a glow plug (with washer attached).

//greg//

 

[JohnS]

Re: No \"glow\" Glow Plugs

If the ammeter was pegged at -30 amps, all three were probably working at one time. I believe each one will draw a little less than 10 amps. Good luck in your troubleshooting.

 

[greg_g]

Re: No \"glow\" Glow Plugs

Shortly after pegging the ammeter at 30A, one would expect the 30A system fuse to blow. Of course you'd know that soon enough, if ALL of the electrical devices quit working.

A good Jinma glow plug at ~50F should typically show about 0.7 ohm resistance on a decent multimeter. When testing installed glow plugs individually, you must disconnect the 12V wire (and bussbar, if so equipped) and measure resistance from the center conductor to the negative post on the battery. But I've found that more accurate readings are obtained with them uninstalled and cleaned up (keep track of the little copper sealing washes). Off the tractor, they're ohm'd between the center conductor and the threads. Keep in mind, resistance varies with temperature. The colder it gets, the higher the resistance. Higher restance pulls more amps.

Typically, ~0.7 ohms at ~12v pulls ~8.4 amps. Multiply that by three glow plugs in series-parallel, and expect to see ~ 25 amp deflection on the ammeter - unless it's one helluva cold day. If/when it gets cold enough, it may become necessary to change to a higher rated system fuse.

//greg//

 

[greg_g]

Re: No \"glow\" Glow Plugs

</font><font color="blue" class="small">( This whole theory may seem 'half baked' and I have no knowledge of any current limiting feature in the Jinma tractors. )</font>
There is no control system on a Jinma, Steve. No voltage or current limiting, no temp sensor, no timing relay. And the glow plugs are connected in series-parallel. I know that sounds contradictory, but consider that Yangdong typically gangs the glowplugs with a bussbar (jumper wire on the deuce). That means that all glow plugs are getting a nominal 12v when applied, but that the failure of one glow plug will not block the voltage to the rest. No different than Xmas tree lights; they all get the same voltage all the time, no extra voltage is redistributed if/when a bulb burns out.

The series-parallel configuration makes testing from the bussbar to ground pretty useless, as you can't tell which - if any - may have changed value. And since you'd be looking for a mere 0.7 ohms, using any arbitrary location on the block for ground is an iffy proposition at best. They're best tested on the bench, after being cleaned. But on the engine it's a must to test them individually, using the battery negative post as reference ground.

Since the ancient Jinma glow plug system has "no moving parts", glow plug related problems are quite regularly tracked back to either the ignition switch or the supply circuit. I had one switch that gave the proper 12v in both HEAT positions, but had an internal short that supplied a ~9v in RUN. Needless to say, that's not "glow plug friendly", but surprisingly it did no permanent glow plug damage - just a lot of carbon buildup. The OE ignition switch is junk; prone to internal wafer collapse, spring breakage, and shorts. As previously mentioned, a Ford diesel switch is infinitely more reliable - plus adds the advantage of applying glow plug voltage in the START position. After replacing the Jinma switch with a Ford, the (cleaned) original glow plugs worked just fine.

FWIW,
(a) the electrical path is battery>starter solenoid>system fuse>ammeter>ignition switch>bussbar/jumper>glow plugs.
Semi-skilled assemblers sometimes short out a 12ga supply wire, which in turn takes out the system fuse. If it's not replaced with at least a 30A fuse, it's likely to blow the next time the glow plugs are heated.
(b)The "30 seconds max" recommendation is based upon battery abuse, same as the " don't crank longer than..." recommendation. It doesn't take much imagination to quickly realize that pushing ~25A down a wimpy little piece of 12ga wire can be unhealthy to the wire.
(c) It will run rough, till compression heating on the other cylinder(s) catches up. But one glow plug can and will start a Jinma diesel.

//greg//