Low Oil Pressure on Newly Rebuilt 2.3 OMC

Joined
Jan 2, 2011
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15
Hello Master Mechanics, I put together a 2.3L this winter, I had low compression and a lot of blow by from my used boat. I had 2 cracks in the old block, found a short block and rebuilt, rings, bearings, head was taken to machine shop and rebuilt, I asked to make sure it was checked for cracks... So once the engine was put back together and started, all seemed good, except low oil pressure only about 12 to 15psi at idle and only about 20 as I reved the engine. Pulled pan off, took a close looked at the pulled oil pump, did not see any signs of wear, I did not replace the oil pump that I had used on the old motor but it had good oil pressure. I plasti gauged mains and rods and was within specs for this 88 between 2 and 3K clearances on rods and mains. I pulled timing belt and ran the pump with a cordless drill, I could feel the pump building pressure but it would not move the oil pressure gauge, I ran a straight line(unrestricted) from the oil gauge port to an open container to see how fast the oil would pump out using the drill. It was not much and I could stop the flow with my thumb over the hole. I did pull the valve cover off and with the drill did see oil coming from the cam shaft. BTW the engine did not have any unusual sounds. Any suggestions as to where to start looking, I have thought about tearing everything back down and checking all ports, on one note when I pulled it back apart after running the engine for less than an 1 1/2 the oil looked pretty yucky, I figured it was the assembly grease used. I have ordered a new oil pump. The only thing close to fit was an automotive 90's oil pump for the Mustang 2.3 engine. I do not see a easy way to pressure test the old pump other than machine a plate with a port and valve and pressure gauge... One stupid question, when priming the pump using the distributor removal method, is it normal for the oil to come up through the chamber in the aux. shaft compartment?
Thank you for your time to read this lengthy post.
Stephen.
 

alldodge

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If your sure its not a gauge issue.
Oil pressure is determined mostly by bearing clearances, and the rest is by the amount of pressure the pump can build. The mains and rods were plastic gauged, and are you sure the cam bearings have correct clearances? If the pump is worn (and it sounds like it is) then its probably leaking internally. Only other thing is if the oil pump bypass valve is stuck open
 
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Jan 2, 2011
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I wondered if that oil pump valve was stuck also, I didn't try to move it while I had it out, I will be taking it out again. When running the aux. shaft to pump with the drill, I didn't see oil gushing out from the cam bearings, but flowing nicely from the cam onto the lifters. I had the boat gauge, electric and then disconnected and put a gauge directly to the oil sensor port. I know the bottom of the rod and mains bearing caps were between 2 and 3 thousands clearance. I have an extra oil pump that came from the short block and it didn't look as good a shape so I went with the better looking one, the one I had in the old motor. I will take a look at it and see how that valve works. THANK You for taking the time to respond. I have worn out everyone in my area that knows about engines or will even listen to me.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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47,300
Always replace the pump and pickup

Your motor is a pinto/mustang/ford ranger motor, pumps are cheap
 

jimmbo

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May 24, 2004
Messages
12,944
"One stupid question, when priming the pump using the distributor removal method, is it normal for the oil to come up through the chamber in the aux. shaft compartment?"

Do you have access to a Service manual specific to you engine? Or a parts catalog?

Were new lifters installed? Sometimes aftermarket lifters are not quite up to spec on clearances or on any reduced diameter(groove) on the circumference the lifter and can reduce oil pressure
 
Joined
Jan 2, 2011
Messages
15
got a new pump worked out of town, going to jump on it this week, head checked vales lapped used old lifters:-( lordy hope the shop that worked on it figured they were good. I did download manuel and refer to it quit often.
thank you!
 
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