Glow Plugs ... "Do they get WeaK"?

[tmajor]

Since I got my M/F 1529, last fall, it has always seemed to cold start kind of dirty to me. I recently pulled the glow plugs and checked them for visual performance. They did have some carbon deposits, which led me to believe, that they weren't getting hot enough in 15 seconds. They all measured about the same resistance and all glowed. In the initial test, the center G/P didn't appear to me, to be quite as strong. After about 15 seconds. FYI: These NGK G/Ps are $70.00 ea. from a dealer, but can be gotten for less that $15.00 ea. on the Internet



I got 3 new G/Ps and did the same test.



I believe, the new G/Ps allow cleaner cold starting, but it's been a little warmer, so haven't really come to a final conclusion.

 

[MultiMow]

It's not necessarily the GPs heat rise. Heat is only part of the equation. Type of catalytic material and reactivity, is the other. Some OEM and aftermarket GPs use thin layer catalysts instead of solid material. If the catalyst becomes depleted, you could have the same temps and still suffer poor performance.

 

[tmajor]

It's not necessarily the GPs heat rise. Heat is only part of the equation. Type of catalytic material and reactivity, is the other. Some OEM and aftermarket GPs use thin layer catalysts instead of solid material. If the catalyst becomes depleted, you could have the same temps and still suffer poor performance.

I don't quite know, how to interpret that information. It would seem, that you might be saying, "they get weak".

These NGK G/Ps are supposed to be "QGS" (QuickGlowSystem) with a time factor of 6-10 seconds. With 3 of them in parallel, and using an 8 second average time, it would seem that a 24 second "G/P on period" should bring them to optimum performance. (Only 1/3rd of the total current would pass through each.) ??

 

[jaxs]

Comparing $70 each to what some cost would lead me to believe they were never intended to do much work. $15 is dirt cheap but I bet adding a heater to intake air rather than replaceing plugs will do more good.

 

[Steave]

The current induced through the G/P depends on Voltage and Resistance of G/P. As in you set up showing the G/P wired in parallel the current will depend on the individual G/P resistance. (Example: Voltage applied = 12 volt, resistance of G/P = ~2 ohms, current would be voltage X resistance = 24 amps through each G/P and 72 amps total for the circuit.) I'm not sure what your G/P resistance is so I just used 2 ohms for the math layout. Each G/P is going to pull a certain amount of current no matter if you have 3 in the circuit or 4 in the circuit and even more. What will change will be the total current of the circuit.

Increasing the "G/P on period" is not going to get them any hotter. You said the time factor is 6-10 seconds so they should be at their maximum during this time. Of course leaving them on longer will heat the chamber more but not increase the heat of each G/P.

 

[Steave]

As far as your question "Do they get weak?". I would think they'd be like any type of heater element and eventually will wear to a point then short out or burn itself open. Not sure but they do go bad.

 

[tmajor]

(Example: Voltage applied = 12 volt, resistance of G/P = ~2 ohms, current would be voltage X resistance = 24 amps through each G/P and 72 amps total for the circuit.)

Sorry, your calculations are not correct I=E/R for 1 G/P, the current would be 6 amps in your example. And in the parallel circuit the total resistance would be 0.6667 ohms. Which would make the current = about 18 amps.

 

[Steave]

Absolutely correct. For some reason I had power calculations on my mine instead of current. Well I know the reason too many years on one brain. Sorry for the misinformation. I studied electronics once upon a time, back when..........transistors were a coming thing.

That's a good price on the G/P. On Jaxs comment about the intake heater, they work pretty good on my International backhoe and my Belarus tractor but I was thinking that was kinda old school. Look out here I go thinking again.

 

[fried1765]

Comparing $70 each to what some cost would lead me to believe they were never intended to do much work. $15 is dirt cheap but I bet adding a heater to intake air rather than replaceing plugs will do more good.

I have always been afraid of the physical integrity of "cheap" glow plugs.
If the tip of one should break off, what have you got?
Engine tear down ???

 

[TractorGuy]

Have you verified voltage to them? I have read where the relay goes bad on some machines and the indicator still worked but the plugs were not getting voltage.