Loss of oil pressure?

[cardana24]

I have a 3.4L from a 94 camaro in my 1985 Jeep Cherokee. About a week ago I noticed that my oil pressure gauge was not reading as high as it normally did. When I would come to a quick stop the pressure would drop down to 5-0 psi, when this would happen the engine would start ticking. I was hoping maybe an oil change would fix this. So today I cranked the jeep to warm up the engine to get the oil hot to drain. When I cranked it the oil pressure shot up to 80 psi when cold then once it was warm it dropped to around 30 psi (which is not what I have been seeing recently more like 60 psi cold and 20 warm). So I changed the oil and filter. Castrol GTX 5W30, and a ACDelco filter. When I cranked it up the pressure only went up to ~40 psi then once it got warm it was hovering between 5 and 10 psi, then when driving no matter the conditions 2-4k rpm the oil pressure would not go over 25psi, and when I was cruising at about 1800 RPM the thing was showing about 10-5 psi and it sounded like a sewing machine. Then when I would come to a stop/idle it would stay down around 0-5 psi and would continue to tick. So what gives? What would cause this? I have only driven this engine about 2k miles since I put it in and I have changed they oil four times. I am stumped about this. Any help?

[geoffinbc]

Was the engine new or used? If it was rebuild it's most likely is human error, maybe a galley plug loose, maybe the pickup is in wrong. I don't think your gauge is lying because you are noticing audible noises when pressure is low

If it is a used motor you could include some of the problem above plus worn bearings or pump.

[cardana24]

Was the engine new or used? If it was rebuild it's most likely is human error, maybe a galley plug loose, maybe the pickup is in wrong. I don't think your gauge is lying because you are noticing audible noises when pressure is low

If it is a used motor you could include some of the problem above plus worn bearings or pump.

If the pick up fell off could it cause the problems I am describing? When I mentioned I cranked the jeep before the oil change it was on an incline and leaning backwards. That is when it hit 80 psi cold. I am thinking maybe the oil pump was covered in this position. I am wondering about the pick up tube falling off because I put a new pump on this used engine, and I also had a new pick up tube put on the pump. When the guy put the pick up on to the pump for me it was not in the right position to sit right in the oil pan so I turned it more downward to fit in the pan better. I wondered at the time if I should have been able to move the pick up tube by hand (it was not easy but I could move it), but I still put it in. Now I do some off road driving with the jeep and I have super swamper tires on the jeep so it is constantly vibrating. Could the pick up have fallen out and be causing this problem? Should I have the pick up tube welded to the pump? How are these normally attached?

[cardana24]

If the pick up fell off could it cause the problems I am describing? When I mentioned I cranked the jeep before the oil change it was on an incline and leaning backwards. That is when it hit 80 psi cold. I am thinking maybe the oil pump was covered in this position. I am wondering about the pick up tube falling off because I put a new pump on this used engine, and I also had a new pick up tube put on the pump. When the guy put the pick up on to the pump for me it was not in the right position to sit right in the oil pan so I turned it more downward to fit in the pan better. I wondered at the time if I should have been able to move the pick up tube by hand (it was not easy but I could move it), but I still put it in. Now I do some off road driving with the jeep and I have super swamper tires on the jeep so it is constantly vibrating. Could the pick up have fallen out and be causing this problem? Should I have the pick up tube welded to the pump? How are these normally attached?

Any one know?

[IsaacHayes]

I'd not drive it anymore and pull the pan and look.... might be damaged motor with all the ticking too now....

[cardana24]

I'd not drive it anymore and pull the pan and look.... might be damaged motor with all the ticking too now....

I'm not driving it any more until I have a chance to look into it. I have not driven it since I posted this thread. I just wanted your guys thoughts before I cracked into it again.

[geoffinbc]

You should not be able to move it without some considerable effort. It is common practice to tack weld the pickup to the pump body. Personally I tacked it with a tig welder and a bit of stainless rod.

Also consider the pickup could have turned more and may be resting on the bottom of the pan partially blocking the pickup. You need to measure it before you put the pan back on.

[cardana24]

You should not be able to move it without some considerable effort. It is common practice to tack weld the pickup to the pump body. Personally I tacked it with a tig welder and a bit of stainless rod.

Also consider the pickup could have turned more and may be resting on the bottom of the pan partially blocking the pickup. You need to measure it before you put the pan back on.

What should the measurements be?

[geoffinbc]

measure the depth of the pan from the gasket rail and then measure the pump pickup to the gasket rail on the block. You need at least 3/8" from the bottom of the pan to the pickup screen and no more than about 1/2"

[60dgrzbelow0]

Any one know?

That "ticking sound" you hear is due to an insufficient amount of oil and or oil/pressure being available to "plump up" the innards of your hydraulic lifters/tappets ...a sure sign of oil starvation in your engine. If the Oil Pick-Up Tube was inserted loosely in vehicle involved in the dynamics of Off Road Racing and it was neither brazed nor welded in place as is often recommended (betterthanyou), it sits far enough away from the tube insertion point and has enough mass and weight to work itself loose under that kind of unusual driving dynamic.

The other issue that is perhaps as critical is the distance between the Oil Pick-Up Screen Suction Plenum and the bottom of the Oil Pan. If that distance is set casually too close, then a partial vacuum between the screened section of the pick-up and the bottom of the pan can occur and the engine will starve for lack of enough oil being sucked into the opening at higher RPMs.

If the pick up chamber is either canted to one side or the other or is bent upward or set too high in relation to the bottom of the oil pan, when the vehicle is being jostled around, enough oil can go "airborne" inside the crank case and the pickup can suck in enough air to cause the Oil Pump to cavitate and become incapable of pumping any more oil with this ingested air trapped between the Oil Pump gears. With enough air inside there, the incompressible liquid draw that usually allows the pump to draw in fluid and pump it out under pressure will not happen. The resulting cavitation can cause the motor to seize from oil starvation.

If TOO much oil is inside the crankcase, and a functional windage tray is not present, it is possible at higher RPMs for the heavy throws and counter-weights of the crankshaft to grab at the liquid oil and whip it around inside the crankcase into a froth-like whipped cream substance that will essentially convert it from a true liquid medium into a mass of millions of useless "oil bubbles". The Oil Pump can cavitate in this situation as well and the engine will seize as a result of Zero Oil Pressure condition.

As for attaching the tube to the pump, it helps to take a section of copper water pipe, slightly larger that the pickup tube and with a cut out a groove in the copper tube-pipe large enough to slip over the pick-up tube and mate up closely with the outer bulged area of the pick-up tube. Then, take a S/S hose clamp and encircle this arrangement and tighten it down. Once you have measured and assured the correct distance relationships between the pick-up plenum and the bottom of the oil pan, you can hammer lightly upon the end of the copper tubing that sticks out away from the curved "U-Turn" in the Oil Pick-Up Tube until you have drifted it all the way up inside the pump housing. A slight electric brazing on at least two to four points between the tube and the housing should do it ...but not so aggressively that you leave a burn hole anywhere around the tube.

[cardana24]

Wow! Thanks for all of that information. I was told that the pick up was brazed into place. The thing is I was able to move it after I was given it back. It was not easy but I did move it because it did not seem to be oriented properly in the oil pan. Anyway, I just pulled the jeep in the garage last night and I hope to work on it this evening. I will post back with my findings.

Does anyone have measurements or a diagram showing where the oil pick up should sit in the oil pan?

[geoffinbc]

You just need to measure the depth of the pan with a tape measure. Then measure the pump pickup in relation to the oil pan rail. A tape measure and a straight ruler is all you need. Don't forget to account for the gasket. I set mine 3/8" away from the bottom.

[cardana24]

Okay, I am thinking I figured out my problem now I just need to fix it. The first thing I noticed when I took my oil pan off is that my pick up now sits higher than the bottom of the oil pump. The second thing I noticed is that the bolt holding the pump is was loose enough for the pump to wiggle around a little. I am thinking this is why I am loosing oil pressure, I am guessing it is spraying out of the sides where it meets the block. As I figured my oil pick up can be turned easily by hand so I need to get that spot welded into place. I took some measurements. From the top of the pan to my pick up it was ~5.5". From the top of the oil pan to the bottom of the oil pump it was about 6.25". From the top of the oil pan to the bottom of the oil pan it was about 7 1/8-7 1/4". So what I am thinking I will do it is make the pick up hang down .5" further than the oil pump. That should put it at about a 1/4 to 1/2 an inch from the bottom. Does this sound like it would be a good plan?

Also does the oil pump call for a gasket? I did not notice one in place. Thanks for the help.

[cardana24]

so does this sound like a good plan? I have someone lined up to weld it tonight. Looking at the picture in the haynes manual it appears that the pick up should be just below the bottom of the oil pump.

Also, do I need a gasket for the union where the oil pump and block meet? I do not see one listed on Advanced Auto's site, but I know that does not mean much, and nothing is mentioned about one in my haynes manual.

[geoffinbc]

Sounds like Cherokees use a 2WD pan. Fair enough.

DONT measure from the pump body. Put a straight edge across the pump screen and measure to the oil pan rail to measure pickup depth

Put a straight edge across the oil pan gasket surface and measure to the bottom of the sump to find the pan depth.

The crushed thickness of the gasket is 1/8" so don't forget to add that. Set your initial clearance at 3/16~1/4" and when the gasket is in the picture you should have perfect clearance.

Torque that bolt to spec and use thread locker. There is no gasket but I used anaerobic sealer to seal the pump to the main cap. It is not necessary but I figured I would do it anyway.