Farmall Cub

How much oil pressure does it take to make the oil light go out? Can I test the pressure switch with comressed air to see if it's working? If so, how much pressure should I use?
I have a new-to-me 154 that had the light disconnected when I got it so I don't know if the switch is working properly or if I don't have any oil pressure. After priming the oil pump and removing the spark plugs and oil filter, I see just a dribble of oil coming out of the galley hole when I crank the engine over. How much flow should I be seeing there?
Thanks,
Charlie

Use 10 PSI air pressure to test the switch. No continuity, buy a new switch.

You are not going to have oil pressure until the oil filter housing is completely full of oil.

Oil sending units vary some but most operate in the 6psi neighborhood, so as Eugene said, testing at 10psi should do it. I would connect a gauge to the engine to find out what you actually have.

I changed out the oil pressure switch for one that I know works and still get no oil pressure.
Any suggestions on where to look?
Charlie

What is the history of the engine? Recent overhaul?

Oil pressure regulator valve is located on the left front of the engine. Could be stuck open - usually not. Located under big nut below the distibutor. Remove nut, spring and see if the plunger is stuck.

Guessing the reason the oil pressure light doesn't work is that the engine is worn out.

I just bought the tractor so don't know a lot about its history. Engine had a knock which I found to be worn rod bearings on #4 cylinder. Crankshaft looked smooth so I replaced rod bearings with .010 oversize and put in new rings.
It appears that I am not getting the oil pump to prime so my next step is to pull off the oil pan and check the pick up tube for a leak.
Any other suggestions would be greatly appreciated.
Charlie

seahaul wrote:Engine had a knock which I found to be worn rod bearings on #4 cylinder. Crankshaft looked smooth so I replaced rod bearings with .010 oversize and put in new rings.

Plastigauge the rod and main bearings. Mic the #4 rod bearing journal.

What size were the old rod bearings? Rod bearing clearance? Main bearing clearance? Oil pickup tube in place?

I have finally solved the mystery of no oil pressure. Found that the crankshaft had been turned before and 0.010" bearings installed. #4 rod bearing was damaged so had the crank turned to 0.020" and installed new 0.020" bearings. Still got zero oil pressure. Changed out the oil pressure regulator valve- still no pressure. Removed and examnined the oil pump which was okay.
By now you probably can guess where this is heading. Took the front engine cover off and with a good light, I could just barely see the oil gallery plug hole behind the camshaft gear- note that I saw the hole, not the plug. Plug was missing. Whoever worked on this engine before I bought it left the plug out.
This problem has been driving me nuts for four months! But thanks to finding good information on this site, it led me to look for that missing plug. Thank you to all those who contribute good information here.
Charlie

Glad you found the issue! Do you think theres any damage to the engine from lack of oil?

It appears that the engine was not run very long with no oil pressure. I suspect the guy who sold it to me had it rebuilt, couldn't figure out why the oil light would not go out, then unplugged the light and put a "For Sale" sign on it.
The cylinders were in pretty good shape and did not need to be bored. Just needed new rings on the original pistons. Crankshaft was turned and new main and rod bearings put in. Camshaft, lifters, and valves are good.
I now have great oil pressure and compression so it's like a new engine. All in all, I didn't have to spend too much on parts, just a lot of my time trying to figure out what was wrong. I restore Cub LoBoys as a full time hobby so this was a good learning experience. I guess anything that makes one smarter is a good thing.
Thanks Gary Dotson and Eugene for your help.
Charlie

Yep, this board saved me an engine as well! Machine shop failed to replace the oil galley plugs and I caught it BEFORE starting my part of the rebuild--really dodged a bullet there To use an old cliche: Forewarned is forearmed This forum has been a boon and a bane. Gave me the MCC bug, but also taught me how to fix 'em