I’d been having a bear of a time getting any oil pressure in this thing. Have a new OreillyZone gauge cluster that came with a thin plastic line for oil pressure, hooked it up to the outlet in the block above the starter motor. Did everything I could think of and then everything I found online to get pressure, but could never get more than a very slow push through the clear plastic line, and the gauge never moved off the peg.
Blew out the inlet/outlet line to the pump with compressed air to make sure no plugs.
Took out the flathead plug above the oil pressure regulator, fed 1/2 qt of oil into it and blew compressed air into it, could hear the oil in the pan bubbling like blowing into a soda straw, so no blockages there.
Replaced the pump itself with a backup I had, and packed it full of vaseline to try to prime it. Took spark plugs out and cranked for 60 seconds at a time, twice. Nothing.
Finally, decided to take the oil pan off to see if the pickup was blocked, bent, whatever. Looked fine to me. But I noticed... The oil pickup screen is surrounded by an upside down cup looking thing. I got to thinking... when you fill the crankcase up with oil, wouldn’t this upside down cup trap air, like putting a cup facedown into a bathtub? The pickup holes are up inside the cup itself, so theoretically it would be in the air pocket.
So I took a drill, put a small hole in the side of the cup toward the top, thinking this would allow the oil to rise up into the cup and thus to the pickup holes. Sure enough, I reassembled, cranked it over, and...
Boom. 25 pounds at idle, 40 lbs on rev.
Now, I’m sure this isn’t the approved way to do things... Perhaps the pump is supposed to suck the air out of the pocket and allow the oil to rise up to the pickup holes? But our pump is pretty worn, so maybe it’s not able to do that the way the manufacturer’s intended. Anyway, this worked like a charm for me, and I’ll proudly file it into the ledger of redneck fixes this car has seen over its lifetime. ;D
Hope this can help somebody!
Very interesting stuff. Is your 30u the new style with mechanical fuel pump. Does your oil pump have a port for a vacuum fuel pump. It seems that when the vacuum fuel pump is hooked up oil pressure takes a bit longer at first to pump up to an operating level. If it is not hooked up and open, you will have trouble pumping up oil pressure. I think your observations are correct and very interesting.
Mine has the gear-style oil pump with no vacuum port. The only vacuum line on the whole car I can see is one coming off of the intake manifold which I suspect goes to the wiper motor? Not sure though.
You're correct the vacuum port on the intake is for the wiper motor. I am very curious about your issue and how it was fixed. Here is a photo of my engine while in the repair shop.
(http://www.1948plymouth.info/galley/var/resizes/chetbrz/Motor078.jpg)
What you have said seems to make sense and you can't really argue with success.., but I would still want to understand if your fix was just compensating for another issue or fixing a inherent engineering oversight. I wish I could talk to the engineer that designed the assembly and find out what he was thinking.
Hello Chet , One thing that struck me a odd when I first looked at this pic you posted . Was the routing of the pump infeed . the fact the the copper tube causes a bubble in the system by going higher then pump for so long . I then checked my BOI . Mine is run and shown run below; coming up left side . Note i have same engine as celledge's 30U . This would require a lot less pull to prime .
Hi Tom, On the 29 the left side hooks up to the vacuum fuel tank. So in my case the left side is sucking air and the right oil. It's amazing that it works.
I do not think so . the left is in from oilpan the right is out back to engine then across to pressure regulator . Do you have a pic in your BOI .
Tom the engine is laying on its side. The right side of the picture is the front of the engine.
What does BOI mean.? Sorry I'm not good with text shorthand. I'll post additional pictures tomorrow can't do it with this phone.
BOI is Book Of Instruction ie. owners manual . Shows diagrams of systems and pics of components . On looking up your 29-29 the way you have infeed run matches . However it changed in 30 or 31 to going under and up to pump . Perhaps they saw this as a problem . I did see older 28-29 with the fuel vacuum tee tap that had line run under and up like mine . Wonder if a service bulletin was ever put out for such . I'll look for pics again .
Tom,
The 28/29/old style 30 without a mechanical fuel pump use an Oil/Vac pump. This pump is designed for two purposes. Vacuum and oil pressure. See picture below of my pump prior to the rebuild. I didn't check the part numbers but I would bet they are different between the new 30 U and the old 28/29.
(http://www.1948plymouth.info/galley/var/resizes/chetbrz/Oil-Vac01.jpg)
PS. If you plug the vacuum line you get an additional 5 psi of oil pressure.
Here is the pump on my early 30-U with a vacuum tank. Slightly different than the '29 pump.
Quote from: crelledge on June 12, 2020, 11:56:44 PM
I'd been having a bear of a time getting any oil pressure in this thing. Have a new OreillyZone gauge cluster that came with a thin plastic line for oil pressure, hooked it up to the outlet in the block above the starter motor. Did everything I could think of and then everything I found online to get pressure, but could never get more than a very slow push through the clear plastic line, and the gauge never moved off the peg.
Blew out the inlet/outlet line to the pump with compressed air to make sure no plugs.
Took out the flathead plug above the oil pressure regulator, fed 1/2 qt of oil into it and blew compressed air into it, could hear the oil in the pan bubbling like blowing into a soda straw, so no blockages there.
Replaced the pump itself with a backup I had, and packed it full of vaseline to try to prime it. Took spark plugs out and cranked for 60 seconds at a time, twice. Nothing.
Finally, decided to take the oil pan off to see if the pickup was blocked, bent, whatever. Looked fine to me. But I noticed... The oil pickup screen is surrounded by an upside down cup looking thing. I got to thinking... when you fill the crankcase up with oil, wouldn't this upside down cup trap air, like putting a cup facedown into a bathtub? The pickup holes are up inside the cup itself, so theoretically it would be in the air pocket.
So I took a drill, put a small hole in the side of the cup toward the top, thinking this would allow the oil to rise up into the cup and thus to the pickup holes. Sure enough, I reassembled, cranked it over, and...
Boom. 25 pounds at idle, 40 lbs on rev.
Now, I'm sure this isn't the approved way to do things... Perhaps the pump is supposed to suck the air out of the pocket and allow the oil to rise up to the pickup holes? But our pump is pretty worn, so maybe it's not able to do that the way the manufacturer's intended. Anyway, this worked like a charm for me, and I'll proudly file it into the ledger of redneck fixes this car has seen over its lifetime. ;D
Hope this can help somebody!
I think we veered away from the main point of this thread.
Finally, decided to take the oil pan off to see if the pickup was blocked, bent, whatever. Looked fine to me. But I noticed... The oil pickup screen is surrounded by an upside down cup looking thing. I got to thinking... when you fill the crankcase up with oil, wouldn't this upside down cup trap air, like putting a cup facedown into a bathtub? The pickup holes are up inside the cup itself, so theoretically it would be in the air pocket.
So I took a drill, put a small hole in the side of the cup toward the top, thinking this would allow the oil to rise up into the cup and thus to the pickup holes. Sure enough, I reassembled, cranked it over, and...
Boom. 25 pounds at idle, 40 lbs on rev.
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Any thoughts on the idea that the oil strainer is inhibiting oil from rising to the input port. ? Thus the need for a small hole ? I have noticed that with the vacuum fuel pump connected the initial start takes a little time to pump up run pressure. Could this little hole fix this deficiency ?
PS... RussT Thanks for the picture.
Hey all, interesting to see everyone else’s oil pump setups- I have one of the later 30-Us built, and it has a mechanical pump with no vacuum port at all, and does have the i let line routed underneath the pump rather than over it. Attached a pic so you can see what I’m talking about.
Chet, as for the strainer idea you mentioned, it could be that it inhibits the oil from rising more than normal due to surface tension against the mesh. I imagine if you’re trying to suck air out with a fluid pump to get oil up to the pickup, every little bit of resistance would count pretty big against it. I think the hole helps because it allows the oil to rise up to the level of the pickup on its own rather than relying on a pump to displace the air first.
Also sorry the pic is 90° sideways, that always happens when I upload from my phone.
Now tha'ts how mine is on my 31 engine . It shown that way on my book . I did understand about the tee for air /vac , I was referring to pump relation left -right . not tee . . I do not know what difference internally are on ours .
I did see an explanation about reason for bowl on bottom ,once . I seem to remember to prevent floating dirt from getting to screen .