The Stovebolt Site Forums The Shop Area Engine Shop Help-------No oil pressure!

I have a 61 C20 with the 235 engine. It was sitting for over 8 years in a field when we got it last year. After a lot of work we got it up and running but the engine was smoking. We just finished valves, rings, and lifters and put the engine back together. Started fine but no oil pressure so we quickly shut the engine down. I don't have an oil pressure gauge just the light and it was on and did not go off. We had the valve cover off, and there was no oil coming to the lifters. When we had the oil pan off we pulled the oil pump and did a thorough cleaning, installing it back exactly as it was. Oil pump is in good shape, and there is no oil filter. I would appreciate any thoughts or suggestions as to how to proceed. Since this truck was sitting for so long we may have gotten some sludge stuck somewhere but I'm not sure where to look-------where the access points are and how the oil flows through this engine. I really hope we can fix this without pulling the head again.

First- - - -put a good gauge on it! The idiot light turns off at 7 pounds of pressure, so even a tiny bit of pressure will turn the light off. Next, drop the oil pan and pump again, and pack the cavity around the gears with Vaseline. I've seen numerous situations where a good pump got air-locked and wouldn't pump. While you're into the pump, be absolutely sure the relief valve is closing fully. Also, be sure the wire to the idiot light isn't shorted to ground anywhere. The switch provides the ground for the light, so any other contact with ground will make the light stay lit, even with good oil pressure.

BTW, DON'T use heavy grease, like wheel bearing grease, to pack the pump. It can clog passages elsewhere in the system, and cause bearing damage. The petroleum jelly dissolves completely when oil hits it, and won't create problems.
Jerry

Did you prime the oil system before start up? How long did you run the engine with no oil pressure?

Only ran the engine for a minute or two. No, I didn't prime the oil system--------do you do that by removing the distributer and manually spinning the pump?

Yea, I used a big round shanked screwdriver that would fit down into the slot. I cut off the handle and put it in an electric drill. Spin it up and you can hear/feel a reduction in RPMs as the pump primes.

Priming the oil pump is filling the pump with oil before you install it. Can't get suction if you don't have the oil to seal the rotors. I think that is what Hot Rod Lincoln was getting across.
Truck Tinker

It's possible to install a 235 distributer without the drive tang being seated into the oil pump drive, done it myself, check it out .

I would try the drill on the oil pump method, and watch for oil from the rockers. There are things that can go wrong in a rebuild. If you indeed did not have oil pressure, when it is solved, you will need to look at bottom end again.

Just had another thought- - - - -(two in one day is spooky!) If an oil gallery plug happened to be left out during the buildup, it could be dumping oil right back into the pan and not letting pressure build up. I know on the 250, there's a plug behind the cam gear that's easy to forget. I haven't been into a 235 recently enough to remember if it has something similar.
Jerry

I appreciate all the input. I won't be able to get back on it until this weekend, but am hopeful that spinning the oil pump with a drill will get the system primed. When we re-installed the oil pump we did not fill it with oil, so I'm sure it just needs to be primed. It occurred to me that after removing the distributer it might be possible to pour some light oil down into the pump to help prime it---------any thoughts on this?

You've got to get oil inside the pump, around the gears, to do any good. Spin it all you want, it's not likely to help. You might take a plug out of the oil gallery somewhere, and force pressurized oil into the system that way, but the quickest, and simplest way to make the pump work is to remove it, and oil the gears, or better yet, pack it in vaseline. Sometimes the hard way is the only way to make things work. Good luck!
Jerry

On Saturday we pulled the distributer and spun the oil pump with a drill. The pump primed right away and within a minute or so oil was coming out of the tops of the rocker arms. Put it back together, started it up and the oil pressure was fine. We drove it on and off all day with no problem. Sunday I went out, started it up and no oil pressure again. Went through the same procedure and it was fine again. Monday------you guessed it, no oil pressure again. The only thing I can come up with is when we serviced the oil pump and put it back on, the old gasket was trashed so we made a new one out of regular gasket material. It may be possible that a small leak where the pump seals could cause the pump to lose its prime after a few hours. Anybody else have this problem?

I thought I did but found out that my distributor was not seated down far enought into the block to properly engage the slot in the oil pump. I found out by measuring the screwdriver shank that I was using to spin the oil pump. I measured this against the distributor shaft marked at the point it was mounted. I was about 1/4 inch short. I loosened the bracket around the shaft and kept fiddleing with it and it finally dropped on down into place. No more oil pressure problems.