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Follow Up: 6 to 8 volt Cold Starting

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Jim bobb

11-29-2005 13:22:48

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Well, had a chance to try the JD 420 tractor in cold weather. Starts like a champ at 20F. Cranks over fine at -10F, but a real bear to start. 12 Volt jump changed that tune.

It appears the coil gets a much hotter spark & does crank over faster on 12 volts. I'll live with it 'as is' this winter, but I recommend a full 12 volt conversion & possibly a 6-volt coil with a ballast resistor.

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John T

11-29-2005 15:21:24

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Re: Follow Up: 6 to 8 volt Cold Starting in reply to Jim bobb, 11-29-2005 13:22:48

Jim, Thanks for the update, while on a 12 volt tractor one can use EITHER a 6 volt coil plus an external ballast or a full 12 volt rated coil, a potential additional benefit of using the 6 volt and ballast PROVIDED THE STARTER SWITCH OR SOLENOID HAS THE BALLAST BY PASS SWITCHING CAPABILITY is that while cranking (especially when cold) and the batterys voltage is reduced, one can have unballasted battery voltage on the coil for more spark energy when cranking. If the coil is straight 12 volts and theres no external ballast, then one cant do that by pass trick.

John T

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jdemaris

11-29-2005 20:20:25

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Re: Follow Up: 6 to 8 volt Cold Starting in reply to John T, 11-29-2005 15:21:24

Just adding a few comments on the ballast. Back in the 1920s-30s, Delco-Remy, Auto-Lite, and others had their own different types of systems regarding ballast or ignition resistors. The system you mention is the ballast with fixed resistance and a bypass for cranking. Ford (tractors) tends not to bother with the bypass and uses a heat-sensitive resistor (thyristor) instead. When you first turn the igntion on, the coil gets full battery voltage, but once the resistor warms up - the resistance increases and voltage to the coil drops. It works fine - my 1964 Ford 4000 has it.

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Jim bobb

11-30-2005 08:46:06

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Re: Follow Up: 6 to 8 volt Cold Starting in reply to jdemaris, 11-29-2005 20:20:25

That thysistor is a great idea. Simple & no additional relay interface needed as the JD 420 uses a mechanical switch for the starter.

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John T

11-30-2005 04:27:24

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Re: Follow Up: 6 to 8 volt Cold Starting in reply to jdemaris, 11-29-2005 20:20:25

Thanks JD, Yeppers I knew some Ford products used somethign like that, I didnt realize they used it on tractors also (Im not much of a Ford man lol), one sees a lot of the standard Ford type solenoids with the extra lil (I) which was hot ONLY when the solenoid was engaged and they are used often for the straight by pass systems.

Take care yall

John T

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jdemaris

11-30-2005 07:01:10

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I'm not a Ford fan either -but . . . in reply to John T, 11-30-2005 04:27:24

I'm not a Ford fan either. I grew up around 55 Chevys with 265 V-8s that (in my mind) were far superior to the Ford 272s. So, I never gave Ford a chance - but over the years I've slipped - I own a 1964 Ford 4000 backhoe and also an 85 F250 with a 6.9 IH diesel. They are both well built. I also have a 1920 Model T - which was good for what it was designed for - a very cheap car. It certainly was NOT ahead of its time. Nor were the Model As (I've got three). Chevy, at the time, had much more to offer. Back to the original purpose of some sort of igntion resistance or thermal unit. Ignition coils evolved along with internal combustion engine design and ever increasing
compression ratios and horsepower ratings. Simply put, it takes higher voltage to fire
under higher compression - thus the need for higher spark potential. One easy way to
accomplish that is the use of 6 volt coils on 12 volt systems. As systems evolved in the
automotive industry, tractors companies took advantage of the technology. You mentioned the relay that Ford cars and trucks use that has the "I" bypass built into it. It works nicely on tractors that don't already have a bypass like Delco provides in their "R" terminal. But, on many Ford tractors - they chose the thyristor setup instead. It works, and is nice and simple. Deere often chose a bypass built into the igniton switch that often failed. With the origial use of an ignition resistance unit - the purpose was twofold, one being to protect the battery
from discharge back through the primary winding and thus overheating the winding and
discharging the battery, if the switch is left on and the engine is not running and the
interrupter points are closed. The Connecticut Ignition System and the Atwater-Kent Ignition system both used a
thermostat for primary resistance. The ignition thermostat used a heat sensitive metal
spring with electrical contacts on it, and it would automatically shut off an ignition
switch if it was left on too long and overheated. Atwater-Kent also used a �Polarity
Switch� to extend the life of ignition components. �The purpose of the switch was to
alternate the flow of current from North to South and South to North. Since direct
current is used will all battery systems, a steady flow in one direction has a tendency to
deposit the metal from one point to the other - but by changing the flow of current
occasionally, the deposit will be put back to the other point again.�

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John T

11-30-2005 13:46:10

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Re: I'm not a Ford fan either -but . . . in reply to jdemaris, 11-30-2005 07:01:10

Jd n my ol buddy Buick, I love sparky chat, Im a Nerd you see lol. Speaking of DC current flow and deposit build ups etc., I have read but lost the sources yearsssss ss ago and have no idea of the credibility, before things got standardized at Negative ground in the auto industry, the reason Ford and Chrysler I believe used Positve ground was they thought there would be less corrosion between frame member joints,,,,, ,,,,,the points lasted longer,,,,, ,and theres that thing about its easier to emit electrons from a hot (electrode) to a relatively cooler (ground strap) surface as far as the plugs similar to how a vacuum tube has the heater under the cathode to emit electrons to the plate.

Have you heard or read anything similar or have any thoughts on the above?????

John T

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jdemaris

11-30-2005 14:15:34

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Hole theory versus Electron theory in reply to John T, 11-30-2005 13:46:10

Yeah, I've read about the old arguments of positive ground versus negative. At one time, the choice was made by engineers who believed in one of two competing theories - either the "electron theory" or "conventional theory" - the former predicted negative to flow to positve, and the latter the opposite. What is referred to today as "conventinal theory" was originally based on the "Hole Theory." This postive to negative theory was based on holes left in atoms caused by leaving electrons - these holes then attracting new electrons. It seems that in reality as we know it, there is no ONE answer to it all. And, in actual field tests it has been shown that frames and bodys tend to get some degree of corrosion protection from negative ground systems, whereas postive ground systems have been shown to give slighty better corrosion protecion of wires and contacts.

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buickanddeere

11-29-2005 15:19:46

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Re: Follow Up: 6 to 8 volt Cold Starting in reply to Jim bobb, 11-29-2005 13:22:48

The 8v battery maybe just masking a voltage drop(s) across cables, connectors or a switch.

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Jim bobb

11-29-2005 19:49:23

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Re: Follow Up: 6 to 8 volt Cold Starting in reply to buickanddeere, 11-29-2005 15:19:46

The tractor has high ampacity new cables. The engine is in good condition & does not miss or smoke. A worn out engine is way more difficult to start in cold weather.

I almost believe a hotter spark would improve cold weather starting performance a fair amount.

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buickanddeere

11-30-2005 08:05:52

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Re: Follow Up: 6 to 8 volt Cold Starting in reply to Jim bobb, 11-29-2005 19:49:23

What voltage was across the coil terminals when cranking with the 6v and the 8V battery?

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Jim bobb

11-30-2005 08:43:47

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Re: Follow Up: 6 to 8 volt Cold Starting in reply to buickanddeere, 11-30-2005 08:05:52

I did not check coil voltage while cranking. I did check wires with an ohm meter to the coil & it was about .1 ohm per my ohm meter.

I assumed the wiring is ok.

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jdemaris

11-30-2005 11:33:14

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Re: Follow Up: 6 to 8 volt Cold Starting in reply to Jim bobb, 11-30-2005 08:43:47

A few general comments without getting lost in technical data. A 12 volt system will outperform a 6 volt system in cold weather - even if all is perfect. I've yet to see a single exception. I've got several 6 volt tractors that I prefer to keep that way (for reasons of collector's value and perhaps nostalgia). For those that I want the ability to start when it's -25 below F - I either use a block heater, or a 12 volt battery stuck in temporarily for winter use, or both. In regard to voltage at the coil - at cranking, a 12 volt system coil is meant to perform at 9 volts, and a 6 volt system coil at 4.5 volts. The more voltage you feed to the coil, the more potential spark output and cold staring ability. The downside to this is - as the voltage gets higher, the life of some coils will be shortened, and the ignition points will not last as long, and - in some situations - the coil might put out more spark then can be delivered to the spark plugs (might jump to ground from a bad or wet wire, cap, etc). Deere Company had particular problems when they changed over to 12 volts. Many of their gas engines were lousy starters in cold weather - and subsequently - Deere put 6 volt coils on 12 volt systems - sometimes with no ballast resistor. This resulted in much better starting, but the points didn't last very long. On many of those tractors, if you replace the coil with a generic unit, they become poor starters in cold weather. So, those are just some of the reasons for all the jerking around with ballast and thermal resistors and ignition "thermosats." Today there are many types of high-quality coils on the market that will put out very high voltage (i.e. spark potential) if needed without sacrificing reliability. Couple that with a electronic ignition pickup (like Petronix) and the problem of ignition point pitting/arcing is also solved. I must admit, I don't use any of the high-end modern stuff. All of my high-use tractors are diesels. So - for the limited use equipment, I don't mind changing points and such once in awhile.

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John T

11-30-2005 13:55:04

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Re: Follow Up: 6 to 8 volt Cold Starting in reply to jdemaris, 11-30-2005 11:33:14

JD n my ol buddy Buick man, One of the limiting factors Ive read about concerning points is limiting the switched current to the 4 and 5 amp range to avoid premature burn up. That would mean a total (coil plus any ballast) of around 3 ohms on a 12 volt or 1.5 on a 6 volt system. Running 12 on a 6 volt coil does indeed allow for more energy (volts x amps x time) to be discharged across the spark plug gap although the points will suffer.

I had a longgggg gggg discussion with Texas Denny over on the AC Board a good while back about the Kettering Ignition system, it would have been fun to have yall in on that one too.

John T

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jdemaris

11-30-2005 14:25:10

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Re: Follow Up: 6 to 8 volt Cold Starting in reply to John T, 11-30-2005 13:55:04

There have been many systems designed to cope with the problem of high-voltage versus points burnout. Back in the 60s-70s, when points were still being used, the Capacitive Discharge setup worked okay and cut down current flow across the points. I had several but they didn't seem to be highly reliable.

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buickanddeere

11-30-2005 09:57:05

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Re: Follow Up: 6 to 8 volt Cold Starting in reply to Jim bobb, 11-30-2005 08:43:47

Measuring resistance that low with a standard hand held ohm meter can be subject to error. If there was 4.0 amps and .1 ohm reistance on just one line alone that's just about to make starting misorable. If .4V drop on one line and likely .4V drop on the other. There is a loss of .8V on a system with about 5.0V to 5.5V or 16% voltage drop. There has to be a high resistance connection,wire or switch in there somewhere making trouble. VD is best found by measuring the voltage across a set of switch terminals, from end to end on a cable etc. Try the voltage from the (-) battery post to the coils (-) post at rest and when cranking. Then again but from the battery's (+) post to the coil's (+) post. And of course post to post on the coil. There is VD in there somewhere. Of course with two extra volts with the 8V battery, a drop of 2-3 volts will go unnoticed until the system deteriates further.

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