Oil Pressure Adjustment

[Jesse Delanoy]

My vessel is on its second Atomic Four - this one a Moyer-rebuilt late model that was installed about two years ago. With both of my engines, I have had extremely limited success in being able to adjust oil pressure using the regulator screw located below the fuel pump. I frequently have to motor for three or four hours or more at a time (cruising RPM usually between 1800 and 2000, boat speed between 4.5 and 5.5 knots), and my experience is that oil pressure starts off the end of the pressure gauge (in excess of 60 psi), then drops for about the first two hours. For most of this season, it's eventually settled at around 20 - 25 psi, with no obvious ill effects. I've been adding a turn to the pressure adjustment screw here and there all season, with virtually no effect. This past weekend, motoring back from the Annapolis area (fortunately passing under the Bay Bridge well before the awful truck accident Sunday morning), oil pressure settled at 20, which, although low, still seemed ok for the short term (still in excess of engine RPM/100), but when we dropped to idle in Bodkin Creek, to lower the main prior to docking, the pressure dropped far enough for our oil pressure safety switch to kill the engine.

I got it started again by quickly bypassing the safety switch with a hotwire, from the battery + terminal to the fuel pump (to the Admiral's great admiration!) and we got back in the slip easily enough. Next day, I said "heck with it" and I screwed in the pressure adjuster several more turns until it was all the way flush with the lock nut, and we took her out for a 2 1/2 hour test run under motor.

This time, the pressure dropped steadily for two hours, this time settling at about 30, and dropping to idle took it down to about 17 - 18 psi (well above half of the cruising level). I'd probably be satisfied if I thought that 30 would be my base cruising oil pressure, but I'm concerned as to why there seems to be such little response in adjusting the oil pressure regulator screw. Don says that a nominal setting is typically with the screw extended about 1/2" beyond the surface of the lock nut.

I had essentially the same experience with the regulator screw on my old engine (originally the ball and spring type - eventually replaced with the older pointed rod type, no improvement), could never get the oil pressure to settle at a comfortable level while cruising, and eventually a bearing gave out - leading to replacement of the engine.

I use SAE 30, high detergent oil, keep it filled between the "add" and "full" marks on the dipstick, change the oil every 50 hours, and generally try to keep the engine well maintained. The only think I haven't tried yet is to dress up the seat on the oil pressure regulator, although it seems early for that, as the engine has been in service for just under two years since rebuild, with about 250 hours of logged use. I have a hard time believing that this could improve oil pressure performance as substantially as I would like, but I could be wrong.

I would welcome any comments or suggestions from Don or anyone else who has had oil pressure issues.

As always, thanks for the help!

Jesse Delanoy
s/v Agape
Baltimore

[High Hopes]

Jesse,

Hmm, the identical problem on two engines, back to back? Probably not the engines. I'd look in other areas.

Here is some fodder to help you get into troubleshooting mode thinking.

Perhaps it is the amount of oil. My engine likes a 3 quart change (I don't have a dip stick). How do you change the oil? Do you measure how much you take out? I'd ignore what the dipstick says until you fix the problem. I had a problem with overfilling myself until I started paying attention to how much oil I was pumping out.

When your engine shuts down, do you know if the low pressure is due to low oil? I'd see how much oil I can pull from the engine at that time.

Does your oil pressure sending unit connect directly to the engine? If not, could it be a clogged oil pressure line? Is it the same sending unit you used before on the original engine?

Where is your oil pressure sensor located? Is it on the same line where your gauge is located?

It's probably not a bad gauge if your engine shuts down with a low pressure reading. But, I had problems with my electric oil gauge. I switched to a mechanical gauge and never looked back.

Is oil showing up in your bilge? Presumably the new engine isn't leaking, but do you have a permanent hose connected to the oil pump out tube? Are you really loosing oil?

Was the engine running over 60 psi when you first installed it? Why did you first decide to adjust the pressure?

Is the faulty behavior really exactly the same from the old engine to the new?

All I can offer are these pesky questions as food for thought. Let us know how this gets resolved. This is a very interesting problem. Good luck.

Steve

[Jesse Delanoy]

When I change the oil, my pump seems to drain things pretty dry, though I haven't directly measured the pumpout amount. From there, 3 1/2 quarts gets it up to the full mark on the dipstick. I've never heard anyone suggest ignoring the dipstick, but if there's some reason to assume that "full" doesn't really mean full, I'm willing to consider it.

I have not considered that the low oil pressure is possibly due to low oil.

The sending unit connects directly to the engine through a short brass tube inserted in the port at the front of the block. At the time the engine was changed, I continued to use my old sending unit and cockpit pressure gauge. Shortly thereafter, I replaced both with new ISSPRO units from Moyer, without much effect.

I don't see any oil collecting in the bilge. I do seem to be burning a bit of oil, but the amount has dropped to less than one quart between oil changes. As I noted, I don't let the oil get below the add mark on the dipstick.

[High Hopes]

Jesse,

On the dipstick, the marks on the dipstick used to be calibrated with marks to accommodate different engine angles. Some engines are sloped steeper than others to the prop shaft. More oil slops back with steeper angles. I also understand there are two dipstick models?

If your engine is slanted a lot, it might be low oil. Your problem is a tough nut to crack. I’m challenging normal assumptions.

It sounds like the gauge is working (both of them – the old one and the new).

From what you say, it sounds like low oil is not a problem, but you don’t seem sure. I’d nail this down, one way or the other. Sometimes you find other things when working to verify something else.

Where is your low oil pressure sensor? Is it on the same line/port as the sending unit? Could the oil pressure be reading low in one place (the low press safety switch) and higher in another (the sending unit)? Maybe you want to swap the location of these sensors and see what happens?

The smoke you mentioned may be a clue. This can be due to too much oil. Change oil and refill with at least a full quart less. The engine will probably run on much less than the 3 1/2 quarts you are putting in. I'd try two quarts and fire it up. A quart usually stays behind, maybe more if the engine is tilted a lot.

Steve

[High Hopes]

Almost forgot, if you don't have a stiff pipe adapter like the one Don sells for pumping out oil, get one. That is the only way to be consistent about the amount of oil you pull from the engine on a drain to drain basis.

[MikeB.330]

have you tried removing the entire regulator from the block and "dressing" the seat? That just may do the trick.

Mike

[Bob Mosher]

Oil Pressure

Jessie/ Steve. I have also been plaqued with oil pressure problems after a complete engine overhaul about 5 yrs ago. All internal parts were replaced with the exception of the oil pump itself (new replacement not available) Upon starting the engine the oil pressure hit 70-80 lbs then drops down to the 40 mark. (I have an electronic and mech gauge attached. The engine will then run for an hour or so then the oil pressure drops to around 20-25 lbs at 1500-1600 rpms. I have taken the engine out several times.and had bearings etc mic'd for fit etc. Everything is well within spec with no visable problems apparent. I ordered a replacement oil pump from Don but there was more wear on it than the original so I returned it. Don advised in an info bullentin last year that this problem was becoming more prevalent and the actual cause is unknown. I wonder if I dislodged some sludge in the oil pump when I had it appart and cleaned it prior to re-asssembly. I am now using 10-40 Castrol M/C oil. It seems to maintain the pressure better. I am open for any ideas . The shop That did the machine shop work is a very respected shop. The agree with Don that 20 lbs oil pressure is suffient for 2000 rpm. Bob

[hanleyclifford]

low oil [pressure

Allow me to join the group with low oil pressure concerns. I used to think the main issue was high hours only but recently have come to look at it a little differently. Those of us who carefully rebuild to spec, have we considered crankshaft end play and connecting rod end play? These are all points where oil presssure can bleed off. I have installed an oil cooling system which operates on a separate pump from the engine circuit. I have verified that it is good for an additional 5-7psi at cruising speed. Also I have opened up the oil pickup elbow to 1/4" npt. These are good moves for those of us with older high hour engines. I am always eager to hear additional ideas.

[Jesse Delanoy]

So far this season, oil pressure seems to be settling down at a point between 25 and 30 pounds (my ISSPRO gauge has marks at 20 and 40, and the settle point seems to be a bit below halfway between these two) while cruising at around 1800 rpm. We cruised under motor on Sunday for about 5 hours (no wind!), and it remained at this point.

I guess I'll just have to live with it.

[hanleyclifford]

oil pressure

Jesse - You never mentioned what coolant temperature you were running. There exists a direct and intimate relationship between engine temperature and oil pressure. If you are starting up with 60psi and steadily dropping to values in the 20s and 30s, you have exactly the same symptoms I have been dealing with. You do not have to live with less than 30psi. Obviously, you would have to pull the engine to check crank and rod endplays or make a change on the oil pick up, but you could start cooling the oil right away if you are handy in the engine room. If you are interested I will provide detailed instructions. Think it over, Hanley

[High Hopes]

I am headed out to my boat today. I will take notes on the oil pressure if I get a chance to start her up.

[thatch]

During the teardown of my spare A4 it became apparent that because of the relatively small size of the oil pump, that oil control would be an extremely important part of the rebuild. As Hanley has noted, the street L on the pickup is a definate place for restriction (I drilled a considerable amount of factory casting flash from that elbow) but increasing it to 1/4" is certainly a good idea, if done correctly. Aside from the main, rod and cam bearings the two other logical places for to look at for pressure loss (3 if you still have the valve chamber spray tube) are the idler gear bushing and the transmission lube hole in the end of the crankshaft. The idler gear is fed by a 3/32" oil hole in it's mount and could, if badly warn, decrease overall pressure. The crankshaft hole is only 1/16" so, if left alone, should not drain too much pressure from the system. Hopefully a machinest during crankshaft cleanup hasn't unknowingly enlarged this hole thinking he was helping oil flow.
Tom
P.S. I have a theory concerning the "low oil pressure at startup, increasing as engine warms up syndrome" if anyone is interested.

[David Masury]

thatch, I would be very interested in your theory on why the OP increases as the engine warms up...

David

[thatch]

"Thank's for asking"

David,
When Universal designed our beloved A4 I feel that they had a little bit of a "lawnmower engine" mentality about it, that is that it would be used, be serviced and be retired at some point. This is borne out by their use of a sort of "lifetime oil filter" installed in an inexcessable place inside the motor. During the teardown of the previously mentioned A4 I noticed that the oil pump pickup screen was about half clogged. It is made of brass wire (.010") and has a grid of 40 strands per inch which by my math leaves openings of about .015". Despite having about 36 square inches of material, at some point it will begin to plug reducing oil flow. Since cold oil dosen't flow as well as hot oil, this screen is now able to flow the hotter oil actually better than the cold. Unfortunately, short of some type of oil system "reverse flushing" procedure, there isn't much that can be done to cure the situation without disassembling the motor.
Tom

[hanleyclifford]

Dead Right

Tom - I like your theory, and of course during this rebuild I have carefully cleaned the strainer. For next time I will begin the design for a much larger pickup screen apparatus to go along with my 1/4" pickup. However, I do not have the "low at start up and increasing pressure situation", quite the opposite. I may, however, change cranks due to the .016" end play; hate to do it though, the engine runs so well (so loose)! Keep talking on this one.