Need Help with oil pump priming issue

Greetings all,

Its been a long time since I have posted, so please be kind. I started a 63 CJ5 build a number of years ago that, for a number of reasons, had to be put on the shelf. I have restarted the project now and am in the process of getting the engine started to make sure everything works before I spend more money. I have been back lurking on the site in recent months and know a lot of the rules have changed. However, I see many names of guru's I still remember.

I have a 1880's Buick 4.1L that has been completely rebuilt. My problem is that I cannot get the oil pump to prime. This post may get lengthy so let me briefly let you know the things I have done already and the one thing I know I have not done yet that I am trying to avoid.

The pump has been with packed with petroleum jelly umpteen times. I have used most a container of the stuff already.

The timing cover is new. The pump gears are new and the end-shaft tolerances are within spec both with and without the gasket. I have tried two gaskets to increase the space just to have something else to do.

I have poured oil in the pressure sending port countless times.

On my last attempt, I tried a trick I found on the web that tries opening the filter relief valve and pulling oil in thru the pressure switch port by turning the engine backward slowly.

The high pressure relief valve is not stuck open. I checked it several times. The relief valve in the filter housing is also not stuck. I replaced the filter adapter and now have both new relief valves.

I am turning the pump the correct direction. In fact, I have turned it for quite a while both directions to no avail.

I have attempted to use a hand pump to push oil into the system thru the pressure port, but do not really have a good pump to test it with. I have seen on the internet where some people use pump sprayers to pre-lube a system. I am still thinking of a way to try to push more oil in.

I have over filled the crankcase. I have tipped it from one side to another. It is currently about a quart over full. The oil pick up tube is new. I have dropped the pan and placed another new gasket where it attaches to the block.

Using a priming tool and a light-duty drill, the pump turns freely and does load up as the system fills with oil.

Right now I have a clear tube connected to the pressure port. Spinning the pump will slowly raise the oil in the tube and it will drain back some after I stop. However, with a mechanical gauge attached there is no pressure. It would not even fill the little plastic tubing that goes to the gauge during earlier tests.

Since this is a new timing cover, and it has been so long since I built the engine, I cannot remember whether I checked the timing cover for casting flash over oil passages at the time. For the sake of argument, lets say I did not. I have been hoping to avoid that.

Any ideas would be greatly appreciated. I know you guys like pictures, but I am not up to speed on what we can put in a post or not these days, or how for that matter. I hope to post a picture of the engine as it is in the photo section of my profile.

The Jeep in the picture is my CJ7. That is a whole 'nuther discussion.

Thanks for listening.

 

Think maybe the pump impeller could be loose (spinning) on the pump shaft when it builds some resistance? Seems unlikely though.

Possibly a partial blockage on the intake side? Does applying suction on the output side clear tubing draw adequate oil through the pump?

 

I thought about the gear issue, however, I didn't have another one to put in its place and It felt tight with my hand. I didn't want to mess it up trying to twist it harder. As to the oil, I will try my little pump and see how much oil I can pull thru the tube. I've made my arms sore trying to push it thru there. Even this far south, motor oil is getting a little slow to pour.

 

I see your signature says Buick 252? You mean 225 ??? If so, I've read that you need to pack the pump with petroleum jelly to get it to prime...

 

Geared pumps can create a tremendous amount of pressure so when you are turning the pump with a drill motor and the oil hits a blockage it would nearly pull the drill from your hands. Did you rebuild this motor your self or did you buy it rebuilt?

 

I built the engine myself. I had the block professionally cleaned, bored and cam bearings installed. Before and during assembly I blew air thru every hole I could find. When I had the pan off recently I removed the oil pick-up tube and blew air thru it again.

Like you I have been waiting for the drill to twist my arm off. No such luck. I keep thinking it is something simple and stupid I have done. Ergo asking you Buick gurus to set me straight.

Meanwhile, I plan to go to my son's shop and see if he has a pump I can use to push oil thru the system a little better.

Keep those ideas coming.

 

Very interesting. I did replace the gasket for the pickup tube, but it could still be leaking. I am starting to think how I can do what you did. I may ask you for more details offline. I tried overfilling the crankcase, but maybe it wasn't enough to get above the pickup tube. Until your post I did not have an idea how much air in the system it would take to prevent the pump from priming. If a pinhole would do it, my hair just got a little thinner and grayer.

 

Sounds to me like priming may not be the issue, possibly just not building pressure. First thing I would check would be the pressure relief valve.

http://www.beforeblack.net/oilsystem.htm

I could be way off base.

 

Don't think you are off base. One of the things i have considered from the start. There are two relief valves, one by the threads that hold the filter and one under a nut on the outer of the pump adapter. In my research, I found some people actually block the relief valve inside the filter housing. One of the reasons I bought a new filter adapter was to get a new relief valve there. I will grab at any straw.

Also, during tests yesterday with the crankcase about a gallon overfull and spinning the pump with a drill, I could see large air bubbles go up the tube then disappear as the tube filled with oil. After the tube filled, it would not run over and there was no load on the drill.

It appears the system gets full of oil will not build any pressure.

Tests today will include blocking the low-pressure valve and checking the high-pressure valve yet again.

I really appreciate the thought everyone is giving this adventure. I keep thinking I will fill really silly when we figure it out.

 

If it was easy, anyone could do it. These challenges develop true skills.

 

Ok guys, I am taking a little break. I couldn't help this nagging feeling that it was something simple. So I went back to the start once again and started questioning everything. In my original post, I stated the pump gear clearances were within spec. I now doubt that. Spoke with mechanic who will re-measure with me one afternoon and also check with engine builder. My money is now back on timing cover, gears and tolerances.

Thanks for helping me think.

 

What Warloch said about an air leak on the suction side (pickup) of the oil pump, makes sense. As the pump turns it will pick up oil due to overfilling/tilting which will cover the air leak and allow the pump to pump oil, as the level drops the air leak is uncovered and the pump will cavitate, aerating the oil-(bubbles) but since air can be compressed, the pump can't function as designed. That's my story....... Any gear -(positive displacement) pump should have relatively tight internal clearances to perform as designed, otherwise the pressurized oil just flows around the gears, takes the path of least resistance = large clearances and goes on vacation, instead of going to work. HTH Good luck!

 

I had a guy rebuild a Chevy 4.3 for me once and we couldn't get oil pressure at start up. Turned out that there are a couple gallery plugs behind the upper timing chain gear that were missing.

 

Another trick you might try.. Drop the pan and hang a coffee can so the oil pickup is inside it. Fill the coffee can so the oil level is above the pickup. Have someone spin the oil pump with a drill and priming tool. Lay underneath and look for the massive oil leak inside the engine. It should be really obvious where it's coming from. It could be as simple as just a missing plug somewhere.

 

Mystery Solved

Ok, Jeep jockeys; if you are interested I will let you know how I finally primed my Buick V6. As I originally thought, it was simple and and somewhat embarrassing on my part.

As it turns out, I think I had an incorrect timing cover. As you may recall mine is the 4.1L, a larger bore of the 231/3.8L. From 1980 to 1985 Buick made a 3.8L for its new front-wheel-drive cars. The timing cover for that engine has a different part number and some vendors will indicate the RWD/FWD model applications. Anyway, after looking at the oil ports in my cover and finally getting a new cover for a RWD model I could easily see the difference. So, I took a drill and opened up a couple of ports on my timing cover and reinstalled it.

It primed in seconds and it puts out over 60 psi with a drill and I have pushed oil all the way up to the rocker arms.

Bottom line, if you have a later model Buick V6 say 1980+ and need a timing cover, make sure you get the right one. It makes all the difference in the world.

Thanks again for all the tips and tricks for priming the pump. I think I have tried them all. I have found that attaching a clear plastic hose to the oil pressure sending port and filling the engine with oil until oil runs out of the oil filter adapter, you will prime without needing to put anything in the gears. When you start to spin the pump, you can see the air leaving the engine, then cap it off before you spin the pump any more and you will be primed in a second or two.

Hopefully someone can learn from my mistake.

Happy Jeeping
Jim

 

Glad you found the problem and posted the fix. Posting a pic of the fix would have been great but guess we can't have it all.