Oil pressure problem

[Rudolph]

Hello I have a rebult 1942 Mercury with a rebult long body oil pump, has about 40 psI but it dropped to 0 the other day when I went up the driveway, i shut it off and opend the oil line and oil came out so i fitted another gauge and that showed 40 psi again, just went on a 200 mile drice and it started to drop down and flutter and come up and down, I wonder if its just the crappy cheap gauge or the oil pump drive gear slipping on the shaft?

[Rudolph]

I am taking the pressure from here but might move it to the filter housing, possibly its getting an air bubble? Just out a gauge on the filter and the pressure is about the same as before the filter it doesn't allways do it

[petehoovie]

Originally Posted by Rudolph

I am taking the pressure from here,

[Rudolph]

I just plumbed in 2 gauges, one in the filter and one from that top fitting, getting more fluctuations in the top one, i just hope the gear on the back of the came has not come loose, the oil pump ones should be good as the one in the bottom of the pump has a pin and the top one in the pump has a very solid pin.

[Mart]

How confident are you re the oil level? It's easy to have mismatched tube and dipstick and have a level that is too low.

[Rudolph]

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Originally Posted by Mart

How confident are you re the oil level? It's easy to have mismatched tube and dipstick and have a level that is too low.

Pretty confident, it holds about 4L in the sump, dipstick and tube came off the same style motor and sump

[deuce_roadster]

I would suspect the spring that controls the bypass loses pressure (or is the wrong one or was left out) when it gets hot and lets too much bypass. It is under the intake manifold at the front of the valley.

[Rudolph]

Originally Posted by deuce_roadster

I would suspect the spring that controls the bypass loses pressure (or is the wrong one or was left out) when it gets hot and lets too much bypass. It is under the intake manifold at the front of the valley.

Its very intermittent tho,

[Rudolph]

Just went for a drive with 2 gauges, pressure was going funny on both of them, it dropped town to 20 psi then went up for no reason

[cadillac512]

I'd certainly be thinking about that gear on the camshaft if it were mine. The symptoms match what I've seen on a couple diesel engine types we rebuild where I work. The gear comes loose on the pump shaft on those (no key or pin) and slips intermittently. Not saying the cam gear is the problem, but it's definitely a concern.


I've not seen a regulating valve behave this way. That would be quite unusual. Not impossible, mind you.


Terry (not much help...I know )

[deuce_roadster]

Do you have a remote spin on filter? Some filters have valves in them too. This is definitely an unusual situation, let us know what is causing this when you find it. Was that a new oil pump?

[Rudolph]

Originally Posted by deuce_roadster

Do you have a remote spin on filter? Some filters have valves in them too. This is definitely an unusual situation, let us know what is causing this when you find it. Was that a new oil pump?

I have the remote spin on filter, with now 2 oil pressure gauges on both sides of it, the pump was rebult with all new old stock parts, pump gear are pinned on both ends

[Rudolph]

Engine build guy reckons that gear if it was slipping wouldnt grab

[Rudolph]

Is it possible the oil pump could get cavitation?

[jimvette59]

The original oiling system has a .060 " restricter in it and 1/4 " lines. I use a restricter at the gauges also. Those lines look humongus JMO

[Rudolph]

Going to fit this thing and see if it will help?

[Rudolph]

Originally Posted by jimvette59

The original oiling system has a .060 " restricter in it and 1/4 " lines. I use a restricter at the gauges also. Those lines look humongus JMO

Its got a 3/4 flow system

[Mart]

If you do not have that piece in place, what do you have in there at the moment? Anything?

If nothing, that will help a lot, I think.

Mart.

[Rudolph]

Used a spare oil pump drive to see if i could feel the cam gear slipping and even if I try to turn it with pliers its not turning so thats not the problem, I will inspect the pump and fit that little thing into the pick up, should there be some kind of seal to the pump to block?

[Rudolph]

Originally Posted by Mart

If you do not have that piece in place, what do you have in there at the moment? Anything?

If nothing, that will help a lot, I think.

Mart.

It has that round tin with the strainer