Oil sending unit test

[militarypotts]

Is their a way to test the oil sending unit on the side of the block?
Can a meter be put on it and if so what reading would I be looking for?
I know the rubber boot holding the wire unscrews, I'm just not sure if a reading can be taken from this point. Thanks.

[Barrman]

There is a way to test the sender. Chapter 9 of the -34 manual should cover it but my electronic copy skips over that chapter. So does the one linked to above.

I have a TM9-8022 which is the 1952 published M35 Gasser manual for everything on that truck. I know it talks you through how to test everthing. It is at home. The pre 1964 M35a2 manual also does this. That is also at home. The newer M35A2 manual just tells you to replace it if the gauge doesn't work.

I will try and remember to look it up manually tonight by turning pages and other old tech procedures.

[rboltz]

Can a meter be put on it and if so what reading would I be looking for?

2 Ohms per Lb of oil pressure. 0 Ohms shut down, 30 Ohms at 60 Lbs. It is linear. It could be off fractions of an Ohm as it is not a precision instrument.

[militarypotts]

So, with the motor running and my meter set to Ohm's, the meter probe is put to the forward part of the sending unit where the wire is connected? Sorry to sound dumb, but I've never done this before.
Is it more likely the sending unit is bad, or the gauge is bad? Thanks.

[WildBill86]

This is interesting...
I too would like to know this.
I read it somewhere in the manual, but I left it at my buddys house when I did the valve adj. last week.
My oil pressure gauge sits at 45+ psi at idle and goes up some when I rev. This seems really high...
Would this be affected by the oil sending unit?
or just the oil pump?

[militarypotts]

I would think that your gauge reading of 45 lbs is in the good range. My stock truck always read 60 lbs, but this past winter started reading 0. Before I happened to notice the gauge at 0, the truck idled perfectly, and very quietly. I'm in the process of trying to figure out if it's the gauge or sending unit.
Having a tough time removing the rubber covers at the back of the gauge to get a meter reading. Also, the sending unit is stuck on the brass T coming off the block.
I've considered removing the sending unit and installing a mechanical oil pressure gauge in it's place. Not sure if this is a good idea or not. I'd like to keep things stock on the truck, but I suppose I could make a new mechanical gauge not noticeable in the cab under the dash.

[rboltz]

2 Ohms per Lb of oil pressure. 0 Ohms shut down, 30 Ohms at 60 Lbs. It is linear. It could be off fractions of an Ohm as it is not a precision instrument.

Said that wrong. 1/2 Ohm per lb of oil pressure. Sorry.

[militarypotts]

My math sucks, but that still means a 30 ohm reading at 60 lbs of oil pressure. Still need for someone to tell me how to set up the test. Also, any suggestions on how to remove the sending unit from the brass T coming off the block? It's tight and may need a second person to hold back on the T.

[rboltz]

My math sucks, but that still means a 30 ohm reading at 60 lbs of oil pressure. Still need for someone to tell me how to set up the test. Also, any suggestions on how to remove the sending unit from the brass T coming off the block? It's tight and may need a second person to hold back on the T.

Yes, a wrench on the "T" block will prevent snapping off the nipple to the block. as for testing the sender, I use air. Put the sender on an air line behind a regulator with a gauge. The sender doesn't care if the pressure is oil or air. Hook up an ohm meter to the sender case and the packard connection. Slowly run up the air pressure and watch the ohm meter with relation to the air pressure gauge. The reading on the ohm meter, X2, should be close to the air pressure gauge reading.