MM RTU wiring and oil pressure

sweinert · Jul 2, 2019

I am restoring a '47 R with my grandson. It has always had oil pressure - as indicated through a cloudy, decrepit gauge - and we have driven it quite a bit since we got it started after probably 10 years of inactivity. By driven quite a bit - I mean we have driven it at least 25 miles. Now we have new gauges installed and realize the oil pressure is pegged at the top of 50 psi on the gauge. I have turned out the oil pressure adjusting screw several complete revolutions and it does not seem to make any difference. Any suggestions? Is this a serious problem? Occasional trips down the road are all that are in the future for this tractor.

Also - this tractor has a distributor - not a magneto. All battery connections - including the starter - were missing when we got the tractor. We have it set up with a 6v battery and a negative ground. Is this correct? It has a generator. Everything seems to work fine. Now showing my tractor/mechanical ignorance - what was the reason for using a positive ground system in the first place?

BMG1 · Jul 3, 2019

Try another oil gauge before you conclude your oil pressure is too high. The quality of some of the new gauges out there is quite poor. If still showing 50+ psi, you may have a stuck relief valve in the oil pump.
All 6 volt systems are positive ground. I think it had something to do with ignition points longevity.

rvirgil_KS · Jul 3, 2019

"We have it set up with a 6v battery and a negative ground. Is this correct? It has a generator. Everything seems to work fine."

Are you asking if it is "correct" or if it is "original". It was originally 6 volts, positive ground from the factory. If properly configured for negative ground I believe it is "correct"

Either polarity the ammeter should show negative with lights/ignition swith on and engine not running. If showing positive reverse ammeter connections.

With distributor, Positive ground the + post on coil goes to side of distributor, with negative ground - post on coil goes to side of distributor.

A magneto is a self contained unit and doesn't care which polarity is chosen for the rest of the systems

Generator needs to be polarized to configuration chosen.

An equipment designer can use bolts with right hand or left hand threads
A baseball manager can use a right hand or left hand pitcher
A tractor/vehicle designer could use positive or negative ground.
It was simply a matter of choice.

MM RTU wiring and oil pressure

sweinert

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BMG1

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rvirgil_KS

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