Glow plug ohms- mystery plugs

[peteinjp]

So I recently bought 8 plugs so as to have a new set and a set of spares.

On my 81 manual glow 2b I replaced the old plugs (ND 067100 1360) with the new ones (YSP PT-109) and turned the key backwards waited my usual length of time- then waited longer- and a bit longer- No glow on the controller. All was well before the switch so I knew it had to do with the difference in the plugs right off the bat. What is weird is that these numbers supposedly match. I put the old ones back in and everything works great.

So I measured resistance on each of the plugs removed from the engine. The Nippon Denso cam in between 2.5 and 3 ohms. The VSP came in at more than double that resistance 6.5 ohms.

The VSP's are stamped PT-109. They are regularly billed as 20.5v plugs that match the toyota number 19850-68040. But I can leave the key in the glow position for a long time and the controller does not even start to glow.

Full 22v at the buss bar.

Any thoughts?

Pete

 

[Dieseler]

Did you hook up the bus bar correctly with the insulators.
Usually if the glow coil does not glow it would mean the plugs are shot or wrong plugs on my 41 the coil would not light up so I swapped in new plugs and it glowed up nice and bright as it should.
What is the voltage rating stamped on the base of the plug

 

[peteinjp]

Did you hook up the bus bar correctly with the insulators.
Usually if the glow coil does not glow it would mean the plugs are shot or wrong plugs on my 41 the coil would not light up so I swapped in new plugs and it glowed up nice and bright as it should.
What is the voltage rating stamped on the base of the plug

Thats the wierd thing- both the old and the new ones are stamped 20.5V and the part number is good too. But the resistance of the new ones are 2 times as high so there is no way that they are pulling the amps needed to get the controller to glow. At double the resistance they will pull half the amps. And I have a hard time imagining that they will not melt after repeated use at 20.5v. I rechecked all new ones and they are good- 6.7 ohms.

pete

 

[Dieseler]

Did your glow coil on the dash glow with the old plugs.

 

[lostmarbles]

So I measured resistance on each of the plugs removed from the engine. The Nippon Denso cam in between 2.5 and 3 ohms. The VSP came in at more than double that resistance 6.5 ohms.

Any thoughts?

Pete

Bad batch of plugs?

I wouldn't place any importance on the different cold-resistance readings. (I have found a similar difference between new and old plugs where they ALL worked fine.)

 

[peteinjp]

D- yep it glow just fine with the old ones. Takes about15 seconds to full glow. Draws 22 amps. Each plug has a resistance of 3.5 so a combined resistance of close to .9ohms. This matches the factory manual specs exactly.

Tom- your point is that the cold resistance reading is of no concern as the resistance will change significantly with temp. I had not considered that. However still its hard to imagine that the cold resistance would be double- though I must admit I'm just shooting in the dark here.

Well I'm not sure how to proceed exactly. I guess I'll remove test a single new plug VS a single old plug and time them to see how long they are taking to get hot. This should tell me pretty clearly if the plugs are in some way incorrect. If the new plugs get hot way too fast then that would indicate an incorrect hot resistance would it not???

I'm still hoping to find that I just did something stupid- but I'm also wondering about contact on the bus bar. As Tom mentioned in his excellently detailed post the new style does not fit so well as the posts and nuts are more narrow. I'll look into this as well.

Thanks Guys.

pete

 

[peteinjp]

Ok- I timed the old plugs and its 20 plus seconds to full glow.

I tried a single plug test. The old plug got hot looking in 16 seconds. The new one took closer to 18 I thought but its pretty hard to know if they achieved the same level of "glow." Good sign I thought as they seemed similar. I wondered if maybe there were contact issues at the glow bar as the nuts under the buss are smaller on the new plugs. I followed Tom's example and put nuts on that would give more contact. I thought surely I'm good to go. But still nothing at the glow controller. I guess I could try for longer but I waited just over 40 seconds and there was absolutely no indications of glow on the controller- and in a darkish room as well. The old plugs start to glow faintly at 10 seconds or so.


Hmmmm,

Do I lay out the dough to buy a new ones at Toyota and give it a shot? I really want these to work after shelling out for 8 of them and having my Mom bring them over to Japan on the plane. Plus the Toyota ones are over $30 each. But these VSP ones are just not looking to be the same thing as what I have in the truck.

Plus I'm just running out of time in terms of dealing with it.....

pete

 

[Dieseler]

Try contacting JAPAN 4x4 here in the vender section he might get them at a reasonable rate.

 

[lostmarbles]

.......I tried a single plug test. The old plug got hot looking in 16 seconds. The new one took closer to 18 I thought but its pretty hard to know if they achieved the same level of "glow." ..............

As you say Pete - It is difficult to tell when you've reached the same level of glow.

So 16 seconds versus 18 seconds is near enough the same to me.

So this makes me think those new VSP plugs are in fact good.

(BTW - I recently purchased VSP PT-104 plugs so I obviously think there's nothing wrong with that brand.)

.. I wondered if maybe there were contact issues at the glow bar as the nuts under the buss are smaller on the new plugs. I followed Tom's example and put nuts on that would give more contact. I thought surely I'm good to go. But still nothing at the glow controller. ....pete

It only takes one plug not making proper contact to cause the controller to stop glowing.

And the big danger here is that while you may feel comfortable that you're not likely to fry anything since your controller isn't glowing ... in fact the opposite is true. Those plugs that are making proper contact with the busbar will now be being fed with EXCESSIVE voltage. And this coupled with the extra glowtime (as you try to get your controller to glow) - is likely to make you destroy some plugs. (I believe this is what happens to the "glow plug serial killers" on this board.) The reason this happens is because the controller glows using the COMBINED current of all 4 plugs (or 6 in the case of an H engine). However when 1 is taken out (by poor electrical contact with the busbar or whatever) there can never be sufficient current to get the controller to glow readily. Yet, because the plugs are connected in parallel, taking one out of the circuitry actually forces the remaining plugs to draw current in excess of what they are designed to take (by exposing them to greater voltage than they were designed to take).

Anyway .... after that warning/sidetrack .......... How about some photos so we can see the condition of your busbar and your busbar-plug connections Pete.

The contact surfaces need to be clean and the nuts need to clamp the busbar firmly.

 

[FinHJ60]

Well, how does it cold-start with these new plugs and "normal" glow-time?

 

[VTCDN]

As all posted above

Great write up. Well understood if you can follow / know electrical.

VT

 

[peteinjp]

Well- actually the truck starts fine with these plugs. And I have the same concern as Tom stated i.e. meltage.

I double checked the connections and did just as Tom using the wider flange nuts to insure a good solid connection. The Buss bar- while not as spanking clean as Tom's- has been cleaned well at the points of connection and works fine with the original plugs. I am sure of there is no issue with connections.

My thinking has been this: If there is enough flow then the Glow controller it will surpass its capacity to transmit the electrical energy will get hot dissipating the energy as heat and light. For example if I shorted the buss bar (and there were no fuse) the controller would definitly glow (then it would quickly melt but that is beside the point.)

In contrast if there is relatively little draw (flow) then the controller will be able to to transmit all the current without surpassing its conductive capacity and as such will not give off energy as heat (Glow.) In my case with these new plugs the controller is not where close to glowing. This indicates that the plugs are in fact of higher resistance value than that of the original as they are reducing the overall flow through the circuit.

It may be that the elements are of a different alloy than that of the originals. However I do have a hard time believing that they would be so different as they should fit OEM specs. Others, such as Tom, have used this brand and have a normally functioning glow controller.

The reason I was not wanting to go longer than 40 seconds is precisely what Tom mentioned which is that I was concerned about melting. I'm wondering if indeed they have been spec-ed incorrectly and actually contain heating elements for a lower voltage system. I don't really want to find out by melting one off into my cylinder either.

I would like to determine definitively if these plugs are within the design specifications or in fact incorrectly manufactured. I think the best solution for now might be to send one off to the manufacturer and have them test it. Of if the manufacturer could supply a valid cold resistance figure that would also help.

I'll get some pics up- its sunny out side so I need to work on getting the roof sealed up before winter......

pics tonight.

pete

 

[lostmarbles]

Taking on board what you say about your glowplug connections being sound with the new plugs ... and that your glow controller won't work properly with them yet works fine with the old plugs .... then I guess that leaves us with no choice but to conclude that your newer plugs are of too high resistance. (ie. They draw too little current.)

Let's put forward a theory here: Suppose VSP has developed more efficient plugs? That is, perhaps your new plugs reach the same temperature as your old plugs in the same timespan yet draw less current? (If so, no doubt VSP are proud of themselves .... but have overlooked old cruisers like yours/mine that have a glow-control system where the current draw is important for proper functioning.)

And if this theory is correct .... I could be in the same boat! While I said I have confidence in the VSP brand ... in fact I see from my records that I fitted the VSP branded plugs (VSP PT104) only to my spare engine. So in fact I haven't tested them at all. (The plugs I'm presently running in my cruiser are actually HKT PT104 plugs that I fitted in September 2008.)

PS. I know one light bulb can be more efficient than another ... but I'm not so sure the same thing can occur with glow plugs. So my suggesting one plug may be more efficient than another maybe utter nonsense. (I know that inefficient light bulbs waste energy as heat but in what form could a significant amount of energy be wasted in a glowplug?)

Anyway, just to eliminate the possibility, perhaps you can do a current-draw comparison between "the new VSP" and "the old Denso" plugs to see if they do draw similar currents Pete? (I have already stated that I have noticed significant variations in cold-resistance readings between plugs that all work well. Hence I am suggesting a current-draw comparison rather than a resistance-comparison.)

If they draw similar currents ... you must come back to the conclusion that the VSP plugs are in fact "good for your application" (and that your connections are somehow bad - only when you fit the new plugs).

 

[peteinjp]

Tom-

If by draw you are referring to amperage then I'm sure I'll see a difference because indeed if the amperage would be the same then the controller would glow. However I do suspect that the Voltage will be higher as the controller will not limit the voltage until it has exceeded its conductive capacity.

Please correct me if I'm wrong here but it is the controller that limits the voltage but it will only limit the voltage after it has exceeded its amperage capacity. I just removed and tested the line to the buss bar and sure enough I get 25.5V- full battery voltage. When I tested it while glowing with the original plugs I got 21 or 22V and I think the voltage would have continued to drop as the plugs heated.

So with that I mind I'm wondering if in fact the new plugs are getting closer to the full 24 or 25V since the amperage is not exceeding the capacity or the controller.


I'm pretty much at beginner level here. I have calculated element lengths for ovens before as it pertains to my own practice (glass worker) however it has been a while. So correct any of my mistaken ideas.

pete

 

[FinHJ60]

Well, I thought that in these basic systems, the limiting thing for the voltage is the battery. When you turn key to glow position, relay connects current, and only thing changing is the controller glowing or not. If it starts ok with these plugs in normal glow time, say like count to twenty, don't mind if the indicator, because you seem to know what you are doing as you are asking here.

My 1981 HJ60 has timer, not glowing indicator. When I turn key to glow position, lamp lights up, and after 15 seconds it goes away, no matter if it's -30 C or + 25 C and if engine is hot or cold. So, in summertime, I glow it for approximately 5 seconds if cold, and in winter, like -15 C, I glow it for the lamp time, and temperatures like -25 C, lamp time + count to ten. Summer or winter, if engine is warm (turned off in two hours) I don't glow it at all.

 

[lostmarbles]

....If by draw you are referring to amperage then I'm sure I'll see a difference because indeed if the amperage would be the same then the controller would glow.......

Yep "draw" and "amperage" I often use to refer to "current flow" Pete. ("Lacking consistancy" is one of my many faults. )

And the fact that your controller should work if the current flow were to be the same is exactly why I am making the suggestion Pete.

My reasoning is ....I think we are probably "clutching at straws" in thinking that your new plugs may be more efficient (and draw less current). .... Because the only way I think they could do that is by reducing conductive losses into the cylinder head. And I see little room for significant gains there - no matter how skilled/resourceful VSP engineers may be.

Similarly I don't think VSP will be interested in your problem unless you have more convincing evidence that their plugs are different/faulty.

...Please correct me if I'm wrong here but it is the controller that limits the voltage but it will only limit the voltage after it has exceeded its amperage capacity. I just removed and tested the line to the buss bar and sure enough I get 25.5V- full battery voltage. When I tested it while glowing with the original plugs I got 21 or 22V and I think the voltage would have continued to drop as the plugs heated.....

I'd express it this way....

The controller will be dropping the voltage to your plugs whenever any current is flowing through them. And the amount the controller drops the voltage is found by Ohm's Law which says V=IxR. Which in this case means: "the voltage drop through the controller" = (plug1current + plug2current + plug3current + plug4current) x "resistance of controller"

This voltage drop I'm referring to is also called a "back electromotive force". That is "a voltage produced by current flowing through a resistance that acts (like an electrical force) in opposition to the main driving voltage". (And the "main driving voltage" in your case comes from your battery.)

...So with that I mind I'm wondering if in fact the new plugs are getting closer to the full 24 or 25V since the amperage is not exceeding the capacity or the controller....

I'll bet your busbar is getting more voltage with those new plugs too Pete.

The fact that your controller isn't glowing with the new plugs suggests this higher voltage is present at the busbar because there is insufficient flow through the controller to make it glow and this creates less voltage drop through the controller ... leaving more voltage for whichever plugs are making proper contact (with the busbar).


When I suggested a "current draw (amperage) comparison" I was thinking of a bench-test Pete. That is, hitting a single 20.5V glowplug with 24V from your battery with an ammeter in the circuit.

While it is true that you will be applying excessive voltage (compared to if the plug was in your truck and downstream of your controller) - it won't do any harm provided you keep the glow period below say 10 seconds (being conservative).

(Remember that a superglow system safely hits a 14V plug with 24V for 6 seconds so we surely aren't risking damage by hitting a 20.5V plug with 24V for the same time period.)

 

[FinHJ60]

I've tested my 20,5 2H plugs driving them 24 volts by cable, it reaches full glow in like 8 seconds, that's as far as I've gone, 'cause in that time you can clearly see if it glows in the tip or by the side. This is the only way to see if plug glows right, old plug can have good resistnce, but it glows in the wrong point.

 

[peteinjp]

Well- the way it stands now i either use these plugs and just count or make a new controller. I got the plug here on Mud so first I'll contact the seller to see if he might take them back- or what I would prefer is to trade them in for another make if possible. If not I guess I'll just have to chalk it up as another lesson learned!

Anyhow- thanks to you guys I know I tested them out well enough to see that they are not a match for the system I have.

I guess there is one more option... adding two more cylinders to my engine would probably get these to work just right!

Best!

Pete

 

[peteinjp]

Ok- so I have done some bench tests etc to really find out if this is a problem with these plugs or something else. I tested the plugs to see how many amps the pull respectively at 24 volts by connecting them directly to the batteries. This eliminates all other possible variables and we can see side by side how these plugs differ.

First I thought I'd put up those pics I took of the buss bar to show that it is clean and in good contact. Basically all the plugs like just like number 4 in terms of contact:

 

[peteinjp]

I don't know how to post pics within text so I'll just write everything and pit the pics at the bottom. The first pic shows the set up. I had to take the nuts off of my PTO winch mount because I don't have a collection of fine thread stuff yet- still new to cruisers!

Then a pic of the plug in an "insulator" clamped to the front of the bib. Each lead was bolted to the battery lead clamps and the test was initiated by putting the positive clamp on the battery nice and tight. The amp meter was testing on the positive lead. As they heat up the amperage varies greatly so I has to time the tests and get readings close to the same timing.