Positive ground? Negative ground?

Scott430 · Jan 30, 2011

My uncle has an Int. B250 tractor. Diesel 144 I think.
My question is, what would happen if someone was to use an opposite ground than what it should be?
The wiring is just basic ignition (starter, generator) with no lights or anything yet. Will the tractor start if the ground is backwards?

Allan in NE · Jan 30, 2011

Yep,

That starter doesn't care how it's fed.

Allan

John T · Jan 30, 2011

YES I agree with Allan. The starter (assuming its an elecromagnetic field) will still turn the same direction REGARDLESS OF POLARITY.

If you dont polarize a genny at the correct polarity you can mess up a Voltage Regulator however. This is a diesel but gas tractors with battery distributor ignitions work best if the ignition coil is at the correct polarity.

John T

JDemaris · Jan 30, 2011

The voltage regulator for the generator won't work, that's all. Nothing else cares about polarity on that machine. And some replacement regulators can be made to work either way.

B250 diesel is kind of an oddball British machine. Predecessor to the B275. No hi-low range in the trans and a strange injection-pump setup on that early BD-144 engine.

Scott430 · Jan 30, 2011

Okay, so no harm done then. I started to rewire the tractor using a diagram that showed a positive ground system, and another guy hooked the battery up with a negative ground and the tractor runs.How do I test the generator to see if its putting out the correct specs?

It blows a ton of black smoke, and sort of lopes?
We just replaced the diaphragm in the injector pump cause it would only run WOT or low idle.

buickanddeere · Jan 30, 2011

If it's been equiped with an alternator. Reverse polarity may make the electricty leak from the wiring.

rrlund · Jan 30, 2011

Seriously,I've never done it,but I bought a forage box from a guy several years ago who had a restored Ferguson 30. He said that his dad bought it new. Said they were hauling hay with it one summer and the battery got bad,so they went to town and got a new one. Said from the time they put it in,it wouldn't start with the starter. It would whirl,but wouldn't start. Said if they pulled it just a few feet,it would start right up and run perfect. He said they finally got tired of messing with it and parked it for quite a few years. Said when his son got old enough to care about it,he wanted to restore it. He said that they discovered that way back all those years ago,they had hooked the battery up to negative instead of positive ground. Said they put a new one in and hooked it up right and it's started great every since.
Why wasn't it starting right with the ground reversed?

Bob Bancroft · Jan 30, 2011

I have changed my old tractors over to negative ground so I could add/run any modern conveniences any time-GPS,radio,etc.)
The best way to check charging is with a voltmeter at the battery.

JDemaris · Jan 30, 2011

I've seen many starters turn backwards when polarity is wrong. That happens when the starter has permanent magnets in the fields.

Not common in most farm tractors though.

JDemaris · Jan 30, 2011

I assume you got the air governor with the butterfly valve the air intake. Check and make sure it's moving and not plugged up.

I've had to fix several B250s and B250s that smoked and would barely rev up because mud wasps plugged up that system. Seems those wasps old IH British-Indian tractors.

You also need to check for plugging from diesel bacteria.

John T · Jan 30, 2011

You ask...

How do I test the generator to see if its putting out the correct specs?

You can start by putting a voltmeter on the battery, and a 12 volt should read around 12.6 if its good and its charged. Then once shes running at fast RPM if the battery voltage rises to the 13 and up to 14 volt and a little over range (depends on battery and VR and RPM) that says the genny and VR are working, but if no rise whatsoever and no ammeter charging indication, its probably NOT (assuming all is wired correct and otherwise okay).

Now to see if non charging is a Genny versus a VR problem, and other generator tests, consult my Troubleshooting Procedure linked below.

http://www.ytmag.com/cgi-bin/viewit.cgi?bd=farmall&th=665110

John T
John Ts Troubleshooting

Scott430 · Jan 30, 2011

As far as the fuel goes, the lines have been cleaned and flushed, the fuel is new. Maybe the butterfly valve is suspect though. Would getting too much air do it too? I currently have the elbow off the intake from the air cleaner to the intake.????

Scott430 · Jan 30, 2011

Thanks John, I will look into this.

John T · Jan 30, 2011

Hmmmmmmmmm, it could have been another problem besides the battery was at the wrong polarity like a bad connection or bad ground very possibly or even a battery problem (Other then wrong polarity). I say that because in all my years as a used tractor dealer and farmer (hundreds of old "farm" tractors were bought, sold and/or used) any size of "farm" tractor (NOT a smaller lawn n garden tractor mind you) ALL HAD ELECTROMAGNETIC FIELD STARTERS that indeed still turn the same direction regardless if the battery got reversed polarity.

The incorrect polarity on a coil ignition can yield a weaker spark but she still sparks. An incorrectly polarized genny can hurt a Voltage Regulator. If the battery got reversed and the genny wasnt correctly polarized the charging system could have been damaged resulting in lowered battery voltage, thats another possibility.

If that tractor has a permanent magnet starter (seen more on smaller lawn n garden type tractors) then incorrect batterty polarity would make her spin opposite.

Sorry, without knowing the starter it used its hard to answer

Hope this helps

John T

John T · Jan 30, 2011

Youre most welcome

JT

buickanddeere · Jan 30, 2011

As Ol' John T said. Weak spark due to the coil polarity being abckwards when the battery wa sinstalled backwards.

rrlund · Jan 30, 2011

That's all I could figure. He never said anything about it turning backwards. Don't see how it could anyway. The bendix wouldn't throw in if it turned the wrong way.

JDemaris · Jan 30, 2011

No, an open intake won't affect anything. The intake manifold has a shutter-valve, just like a gas engine carburetor uses. The shutter senses air-inake speed and operates the governor in the fuel injection pump via that diaphram you said you replaced. If that shutter gets stuck, the engine won't rev. If the air intake gets plugged, the engine won't rev.

massey 333 · Jan 30, 2011

Just a question John T,on a 12V generator that has to be changed from + to - Gr.because the only reg avalable is Neg.Gr.and the only one made for that Gen.is Solid State and can't be polorized,how does the gen.change polority.

Scott430 · Jan 30, 2011

Okay, so the smaller steel line that comes out of the front of the diaphragm I just replaced may be plugged? If I'm understanding you right that is. I'm going off the top of my head here, I don't have the tractor near me so to speak, so I will have to get to my uncles place and take a look at all these suggestions.

John T · Jan 30, 2011

The Voltage regulator IS NOT what gets/needs Polarized its the Generator that requires Polarization so it matches the batteries Polarity (+ or - ground) to charge it.

HOWEVER some VR's wont work correct at the wrong Polarity i.e. they may be for Pos or Neg ground and if its a Solid State VR it needs to be for a specific ground, usually Neg.

THEREFORE if the VR is for Neg ground ONLY and, of course the battery is installed at Neg ground, the Genny needs to be Polarized at Neg ground BEFORE starting.

A typical tractor DC genny can work at either polarity once polarized, you just need a VR that works at the polarity you choose (some will work at either many not so) and have the battery installed to match.

John T

JDemaris · Jan 30, 2011

If that line is plugged, or the shutter not moving, or the intake plugged - it won't rev up.

It's a very odd setup. I think some Ford Majors also use it - but makes sense since all of this is British engineering.

massey 333 · Jan 31, 2011

Maybe I wasn't clear or was told wrong.You can't flash a gen.with a solid state reg.I have done 2 and all that was done was change Battery to neg and no repolorize and all is fine.

Positive ground? Negative ground?

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