No oil pressure

If you noted oil pressure with the filter off, have you replaced the filter? As far as an issue or defect, I'm not familiar with one. Has the vehicle been sitting? Is the oil clean and full?

This is the year make and model vehicle I learned to drive in. It's a big one. LOL

Let me know. Also, let me know if you heard any knocking or ticking from the engine when the light was staying on.

Take care,
Joe

The engine has been run on occasion through the winter. Lots of oil. I shut the engine off real fast when the light stayed on. My next step is a new filter when I get to town. Will putting air through the oil pump show anything?

Honestly, I don't see how that would show anything. I would first try replacing the filter to see if that takes care of the problem. If it doesn't, let me know and we'll pull the oil pump and see what is happening. However, you indicated there was oil pressure when you removed the filter, so in all honesty, it sounds like a filter issue.

Let me know what you find or if you have other questions.

Take care,
Joe

I changed the oil and installed a new filter. However still no oil pressure. I have never heard of oil pumps failing suddenly. Have you?

Under normal conditions, no, but this vehicle isn't driven daily. Didn't you tell me oil shot out with the filter off and cranking the engine?

At this point, we may need to remove the oil pan to see if the pick up tube/screen is blocked. That is another possibility.

Joe

The vehicle isn't driven daily. I did get oil flow with the filter off and cranking the engine. I changed the oil and filter and still have no oil pressure when I ran the engine for a short time. I tried fishing a wire around inside the oil pan through the drain hole but didn't hook anything. I suppose I could pull the pump and test it against AutoZone"s specs.

That is odd. I have to be honest. It sounds like the pump is bad. There could be restriction on the pick-up screen, but the only way to know is by removing the oil pan.

Joe

Thank you for your replies. This is a problem that is not necessarily solved with a simple "replace a component" and you're done. It looks like oil pump removal is next and we'll see if anything is plugged or broken. It could be after 40+ years.

I agree. It needs taken apart and inspected. I'm hoping it's something simple like the screen is plugged. If that is the case, I would remove the pump as well and inspect it.

If you have the chance, let me know what you find. I'm interested in knowing.

Take care,
Joe

With much effort I got the pump removed and measured some of the clearances. The clearance at one wear spot on the cover was a tight .002. At the tip of one lobe of the rotor to the inner lobe of the outer race it was .012. The others were within specs. After the fun of looking for a piece of pipe for a suitable extension handle for my ratchet and a pry bar to hold the socket in place so I could get the pump off, I think I will try to jury rig a vacuum setup to see how easy it is to draw up oil from the pan. If it is easy to draw up then the problem has to be the pump or further up the line. Someone had mentioned a burr on the pressure valve in the pump that caused low oil pressure but I'm not that lucky this time.

Was everything in the pan including the pick-up tube?

Joe

I haven't pulled the oil pan yet. I'm wondering if the few low specs I have for the pump would indicate that it got to the point that it would not put oil through the engine because it was easier to leak back to the pan.

Anything is possible. Considering when there is no restriction (oil filter removed) you get oil coming out which is stopped when you reinstall the filter, it may be the cause.

Thank you for your input. I'm leaning to getting a new oil pump and trying it. If further work on the engine is needed to fix this, a new pump should go on anyway.

I agree. However, most people wouldn't say that. Once it's out, replace it. You don't want to take things apart again in the near future.

If you have the chance, let me know what you find. I'm interested in knowing.

Take care,
Joe

Will do. My neighbor gave me another tip. He suggested trying to turn the pump drive from the bottom to see if the gear and drive rod are still firmly connected up top. I'll give that a try tomorrow.

Sounds like a plan. Let me know what is found.

Joe

The drive gear and shaft are all in one piece so that's another item eliminated.

Good morning,

If I could throw my 2 cents in here, when you removed the filter and oil came out when you started it, that means there should be pressure somewhere.

Since it did not come out the sender hole, did you check to be sure there is not dirt or debris in that passage? That is an area that I would blow back air to see if the passage is blocked.

Also, when you replace the pump, I would pack the gears with luber plate to get the pump to prime quicker.

Did the engine make any noise when you did start it in the beginning?

Roy

I'll try the air pressure trick and see what happens. When I noticed the check engine light I shut it off real fast. I have the defective muffler off so the engine made a lot of combustion noise that may have covered it up.

Give it a try and keep us updated so we can help you more if needed.

Roy

Air pressure from the oil sending unit hole to the pump inlet was clear with only a few drops of oil coming out. Air pressure in the reverse direction with the oil sending unit reinstalled sounded like an air leak in the pan but hard to tell the location accurately.

Pulled the oil pump drive and it's all intact and like new. Looks like a pan removal now. I hate when that happens. Will the pan come off by turning the engine so counterweights clear or does the exhaust have to come off and and engine raised. The net is full of all of the above.

Yes, I would remove the pan and pull the pump. Check for the gears and see if they have any scoring on there surfaces. That would be an indication of a failure.

https://www.2carpros.com/articles/high-or-low-engine-oil-pressure

Roy

My pump is an exterior mounted unit, On my first page of posting I gave some wear measurements on my pump but have not found any information as to how much wear causes pump failure. It's unfortunate that we weren't able to take all the failed pumps that were replaced and the low oil pressure issue solved with a new pump. Those pump measurements would be handy now.

Can you post a picture of the pump?

I am also concerned about the oil pickup tube as well. I know you hear air into the pan but if the tube has a hole in it, it will draw air instead of oil.

Roy

I got the pan off today. No metal in the bottom. Nothing looks discolored from heat, thankfully. No debris clogging the pickup. Here is a pic of the pump. I gave some wear measurements earlier. With the moderate use this vehicle has seen, if a bearing has spun would it be most likely a rod or main?

Have you ever heard of an oil pump on one of these engines or any 4 stroke engine giving intermittent trouble and then operating normally for a time?

Hi,

Honestly, anything is possible, but most times it either works or it doesn't. Now I've seen excessive wear on mains, but that isn't going to stop the pump from working. Either mains or rods will be making noise as well. Was there a knocking?

Looking at the pump, physically it looks good. However, if I recall, there was excessive clearance.

Let me know.

Joe

I didn't hear any knocking because I shut the engine off when the oil light came on. Wouldn't you expect a pump to push oil to the oil galleries and then to the pressure sensor even if the pump was in poor condition?

If the pump was failing, it would have gotten weaker over time. If it was a bearing, I think you would have heard it before you got to this point. So, if there wasn't any engine noise prior, I don't think that is the issue.

At this point, you have the pump out and I would replace it. No sense in putting the old one back in.

I agree with Joe, I do not think it is the issue.

If it flowed oil with the filter off, then the pump was working but the question is how much oil it was flowing.

Roy

Since my last post I had a close look at the o-rings under the pump cover. The body of the large one looked more square than round in cross section. Maybe it was this way new. The smaller one was round in cross section and appeared to have a small dent in it. My local bearing store had o rings that would fit so I replaced them in the pump and gave the pump a good oiling. After reinstalling the pump I spun it with a drill with a container of oil under the pickup. I got oil dripping from various engine parts but no oil at the sending unit. Today I moved the crankshaft a few degrees so I could see further up at the front of the camshaft to check for any problems there. Then I removed the sending unit and my helper ran the pump. The oil appeared and gave me a mess to wipe up. I replaced the sending unit, checked the oil pressure light with the pump turning and the light went out. I have to clean up the pan, get gaskets, etc before I start the beast and see if all is well. Thank you for your responses. I'll post the later results.

Sounds like you got it, good job.

Keep us updated.

Roy

'Thanks to all for being a sounding board for this sudden problem. It appears that all I did was change the oil pump o-rings which solved it. I was doubtful that oil pressure would return when I ran my pump with my drill and no oil came over the lifters but it did come out of the oil sending unit opening. With some concern I started the engine. The lifters got a bath like Niagara Falls. I hope the problem is solved so other spring work can get done.

Good job.

Glad to hear. Let us know if you have any other questions.

Roy