[Voelker0319]

Ok guys I need some advice. I just overhauled the engine in my 89 F-350. Fired it up to discover little to no oil pressure at idle and 15-18 if I rev it a little. So I put my mechanical guage on it. Confirmed my electronic guage readings. So I'm thinking the regulator valve is stuck. Pulled the cooler and checked it all out and it seems to be operating properly. So while i had the cooler off I cranked the engine over, watching the oil port where the cooler mounts in the front and I'm hardly getting a trickle. Added an extra gallon of oil and got the same result. Everything is new in this engine...Oil pump and pick-up tube too. Is there a port I could have missed putting a plug into between the pump and that oil cooler port that could be bleeding pressure off? I'm prepared to pull the engine to examine the pump and pickup tube if necessary. At this point I cant think of anything other than a faulty oil pump or cracked pickup tube. I thought id run it past you guys first in case I'm missing something. Thanks in advance!

 

[oldrebuiltdodge]

On the large engines that I used to work on, we had to prime the oil pump before we put it in. I have used that practice on everything I worked on since it bit me once. If the oil pump was dry when you put it in, it might not be picking anything up. Use a oil can and back flow through the pump from filter inlet port it might help. Fill everything up till it runs out then try it again.

 

[Voelker0319]

Ok but if I had lost prime on the pump I shouldn't be getting pressure when I rev it up. It would be airlocked and would never pump, right? Or am I overthinking this?

 

[oldrebuiltdodge]

It could be still trying to pick it up. Did you use a new pump, or the old one? The old one might have a little wear and need some help.

 

[Voelker0319]

New pump, new pickup tube.

 

[oldrebuiltdodge]

I don't remember, how does the pump deliver oil to the block? Is there a crossover tube, or does the discharge flange directly to the block. It's been better than 20 years since I've looked inside the crankcase of one of these. My point is that the gasket/O-ring might be leaking. If I remember right the flow is from the pump to the filter then through the cooler to the bearings. There might be something on the discharge of the oil cooler too. I believe they made several different gasket configurations for that end of the cooler. wrong gasket, or put in upside down/backwards might be all of your trouble. I would definitely try pulling the cooler before I pulled the engine back out.

 

[Voelker0319]

The cooler is out. I have very little flow out of the block while cranking. The pump bolts directly to the block. There's a gasket on the pick up tube side, no gasket on the pump to block mating surface although i use a small smear of permatex gasket maker. The oil passage runs about an inch up from that mating surface and makes a 90 degree turn to the oil cooler mating surface.

 

[oldrebuiltdodge]

Keep in mind, that pump is positive displacement. Meaning that unless there is something to hold backpressure it won't build any. The flow is only high enough to keep everything supplied with oil. If you're coming directly out of the pump you obviously aren't running the engine, so it is only turning on the starter, probably not nearly fast enough to give you any accurate pressure reading or flow check. Can you hold your thumb over the hole and hold the pressure back? How are you reading pressure? PD pumps are basically lazy, they won't put any more pressure up than they absolutely have to. Having said that, don't ever run one against a completely plugged system, because what goes in is coming out...somewhere, or stopping the pump. That's generally how oil filters get sent into orbit on a good cold morning. If you know what the flow should be, you can run a catch test and see what it actually is, then compare. Keeping in mind the speed the pump is turning as compared to what the test RPM is

 

[Voelker0319]

Well I started it up briefly and put my finger over the outlet port where the cooler mounts and i was able to easily stop all pressure. Im out of ideas other than a bad pump or pickup tube.

 

[oldrebuiltdodge]

About all there is left.

 

[Voelker0319]

My thoughts exactly, Thanks for your input. Ill update when I get it apart.