Weird Oil Pressure Experience

[Doorkicker]

Ok, strange experience yesterday and would like to share to see what this group thinks.

About the car/engine:
It's a 400ci in a '67 Coronet 440. Engine oil was a little on the old side. Oil pres. gage working and tested. I know nothing about the engine/car, just purchased about 3 weeks ago.

Summary of what happened:
Like virtually every other day, I went for a drive in the late afternoon. Oil pres. (70-75 lbs. at cruse) and temp. (200 at cruse, a smidge hotter than I like, but it's been sweltering hot out lately) were good to go. Got home and parked it. Everything was fine.

Got up the next day to do some carb work (adjust kickdown linkage) and then prepared to start the engine.

When it started it knocked and ticked badly (well, badly from my perspective...) and I saw no oil pres. I immediately shut it down. It ran for about 15 seconds, plenty of time to show on the gage.

My actions:
* Pulled the valve covers to check for a thrown lifter by checking the pushrods - all looked fine.
* Pulled the distributor and the pump shaft. Inserted oil pump priming rod to check oil pres. Tested resulted in 0lbs. pres. (yes, I ran CCW). I noticed that the resistance on the drill was very low... as in not pumping any oil.

At this point... I assumed something went wrong with the pump's check valve, such as a stuck valve piston or the spring broke, etc. So, I prepared to remove the check valve.

Next steps:
* Drained the oil and dropped the oil filter
* At this point... and not sure why... I decided to change the oil and filter and test again with the priming tool.

To my surprise, the oil pres. was right back up. Threw everything back together and ran the engine for a while to test. Started, stopped, and restarted a few times.

So, a couple questions for the community:
* Do you think it was a stuck check valve in the pump? I'm asking because would that result in absolutely no pressure?
* What are the odds it was the oil filter's bypass valve sticking?
* Generally, what do you think?

 

[mmissile]

Valve seals blocking oil pickup screen? Bearing moved?

 

[Jerry Hall]

I would pull the pan and check the pickup and the pan for sludge.

We did a brake job on a older Dodge Dakota for an older gentleman, in his mid 90's. While taking the truck back to him, we noticed that the oil pressure went to 0 and we shut it down on the side of the road. I called him to tell him there was additional problems and after describing the problem, I was told that this happens from time to time, and not a big deal. I was told that for the last 70 thousand miles that he only added oil as needed and changed the filter about twice a year. I knew he couldn't afford to have it towed, so I walked back 2 miles to get my truck and trailer. When I got back his truck was gone. I had left it locked and had the keys in pocket. The owner had had someone bring him their and he took the truck. Needless to say he blew the engine on his way home. I picked the truck up, now severally broken. Upon pulling the pan, there was about a inch and a half of sludge. The pickup was almost completely stopped up too.
This is just my warning to check everything you can on a vehicle you don't know much about.

 

[PlymCrazy]

I'm with @Jerry Hall in checking everything you can on any vehicle that's new to you.
How did the oil look when you changed it? Did it look like it had been neglected? That can be an indicator of how well the former owner cared for/maintained the engine and drive train items. Or the entire vehicle for that matter.
Not attacking anyone here believe me. But some folks really stay on top of maintaining these old rigs. However, even then things can still break.
Others drive them until something breaks and only then do they decide to look under the hood.
It's good you got your eyes on things like oil pressure regularly.

 

[beanhead]

So, a couple questions for the community:
* Do you think it was a stuck check valve in the pump? I'm asking because would that result in absolutely no pressure?
* What are the odds it was the oil filter's bypass valve sticking?
* Generally, what do you think?

First, just for clarity BB mopar pumps don't have a second check valve, only that relief valve that opens at a preset pressure. Usually a stuck poppet will give you high pressure as the pump spins faster. I suppose if it stuck open it would give you lower, but not NO pressure.
Just a spitball idea but it sounds like there may have been a temporary blockage at the inlet or filter from who knows what since it was fine after the oil change.
I Like what @Jerry Hall said too....you might take the time to drop the pan and give things a look especially since it's a "new to you" car. I've seen pans with gobs of assembly lube stop up the oil pickup intermittently like that...it happens. Kind of a pain to drop the pan from underneath but worth a look in my opinion.

 

[Daves69]

* At this point... and not sure why... I decided to change the oil and filter and test again with the priming tool.

Maybe open up that old filter to see what it's collected. Should give a hint on what's going on in the pan.

I don't think I'd trust the pump after all this. I had the extreme low pressure scenario on the next morning startup that beanhead mentions on a 360. I heard the poppet snap back as soon as I broke the first pump bolt loose.

 

[Doorkicker]

You guys are rock stars! Thanks for all the notes.
I just got off work and going to cut open the filter and report back. Also, I'm thinking something amiss with the pickup now too. The oil pan isn't too difficult to drop, so I might get started there.

Here are responses to some of the questions:
* How'd the oil look? - Pretty ok actually. Dirty and at first I thought it was this, like it had gas in it. But it didn't appear to have fuel in it. I'm checking the new oil a lot.

* Does it looked neglected? - I would have to say... not so really. It's weird. It looks like someone worked on it with very little money to spend and not a lot of patience. For example, it has a nice eddy RPM on it, but the spark plug wires that are cut-to-length, but weren't cut and the plugs were 100 years old. The shifter cable was routed completely backwards. The throttle linkage is not cheap, but the throttle cable and kickdown are a mess. I would guess the oil wasn't changed in the last year.

In any case, I have three 440 blocks just waiting for me to finish building and stab one in this car. But this 400 is really growing on me, so I want it to be ok

Thanks again fellas.

 

[dvw]

I'd get a $25 remote cell phone camera and look thru the drain plug hole at the pick-up. Easy enough to see if its full of broken valve seal material. Way easier than dropping the pan. If the pick-up was cracked the issue would still be present. One bearing would not cause a complete loss of pressure. Two items would be my guess. First a bad oil filter. It wouldn't be the first time I've heard of zero pressure from a filter. The other would be a hung up relief valve in the pump. That is also a common issue. Only takes a small particle. Easy to take it out and clean. Think simple first.
Doug