89 ford ranger

[lostranger]

Having issues with oil pressure going up and down. And when this happens my has a erratic idle and then truck stalls

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[alwaysFlOoReD]

I just moved your thread today as it was in the wrong forum. If you give some details about your truck that would help with diagnosis. IE; engine size.
Good luck,

Richard

 

[RonD]

Having issues with oil pressure going up and down. And when this happens my has a erratic idle and then truck stalls

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What engine?

I believe by 1989 all Rangers were using oil pressure switches, not senders, so either on or off, no variable pressure shown on gauge.

Oil pressure gauge would either read "normal" or 0, so no up and down of the needle.

I would look at the electrical system, battery voltage and then alternator connection would be my first stops.
With engine off the battery voltage should be 12.5volts(good battery), with engine running(alternator running), voltage at battery would be 13.5volts.
If there was a lose connection the alternator voltage may be cut off, so voltage drops, oil pressure gauge would drop as well; coil, injectors and computer are also running on lower voltage so could act up, engine runs rough.

 

[lostranger]

Its a 2.9. I pulled the valve covers and upper and lower intake.

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[lostranger]

My motor was saying I had good oil pressure but valves were tapping. Pulled valve cover off and started truck barely any oil was making it to the top. And I just replaced the pump

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[lostranger]

I was told if my bearings on my crank were going bad I would have no pressure either that's why I started to break the motor down getting ready for a rebuild

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[RonD]

Pull out the Push Rods and soak them in solvent(cleaner) then blow them out, repeat if needed.
They should go back into the same lifter the same way, not a big deal but if you can mark them then do so.

I think the 2.9l had an issue with a Cam bearing wearing out which caused the valve train noise.
It was a common issue and outside of the noise, the engine would continue to run for a long time.

Oil pressure is Back Pressure, so a new oil pump doesn't hurt but if a bearing gap is large enough it will drop the pressure in the whole system.

 

[lostranger]

Thanks

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[RonD]

You're welcome.

Oil pressure is often misunderstood.
Oil pressure means there is "too much" oil flowing from oil pump..................

The oil pump generates a flow of oil to the oil filter and then to the main oil passage, where the oil pressure sender/switch is located.

If the main passage was open at the end there would be 0 oil pressure, there would be oil flowing but 0 pressure.
The pressure comes from the oil being pushed thru small bearing gaps, crank, connecting rods, and cam.
When there is more oil being pushed than the bearings can pass then you get "back pressure" in the system, so oil pressure in the main passage at the sender/switch.
Too much oil flowing than is needed = oil pressure.

Because of the small passages(friction) and gravity the valve train will have the lowest pressure on most engines, hydraulic lifters help by pumping oil up the push rods, but they rely on being refilled by the systems overall oil pressure.

Generally 6psi of pressure at idle is fine, 30psi at higher RPMs, oil also cools the bearings, higher oil pressure increases the oil flow out of the bearings which helps in cooling at higher RPMs.

But increased oil pressure only increases the flow out of a bearing gap slightly, if flow was increased proportionally to RPM then oil pressure wouldn't go up , it would stay the same, oil pressure goes up because flow from oil pump is increased with RPM but flow out of the bearing gaps stays almost the same, so back pressure increases.

Too much oil pressure can be bad, it will reduce lubrication, and it can also be a sign of a blocked passage.

 

[lostranger]

I found out it might be my oil pressure relief valve might be stuck open

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[RonD]

On the 2.9l that would be in the oil pump housing, and it is a bit of a long shot as the problem.
Oil filter also has a by-pass valve in case filter gets clogged, so change oil filter....even if it is new.

I believe you would need to lift the motor up(remove motor mounts) to get the pan off to service the oil pump.

I would first get a mechanical oil pressure gauge and hook it up in place of the electric sender/switch, then start engine and watch "real" oil pressure as engine warms up and also at different RPM levels.

 

[lostranger]

Ok thanks

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[holyford86]

you can clean the pushrods all you want and it wont do a thing, oil flows to the upper valvetrain through the rocker shafts and to the lifters through one cam bearing. a general rule of thumb is you want 10psi of oil pressure for every 1000 rpm. Specs for the 2.9 want at least 40 psi oil pressure at 2000 rpm when warm. Changing an oil pump usually does nothing for pressure, oil pressure is the resistance to bleeding out of the bearings and other passages, so usually low oil pressure means a worn engine not oil pump. I've had a couple 2.9s one had really bad oil pressure (30ish at redline) and didnt tick at all and the other had 50ish psi at the same rpm and ticked like hell. this is part of the reason why I dont own 2.9s any more.

 

[lostranger]

I did a motor flush put new oil and filter on and had awesome oil pressure for about a hour then slowly dropped off. I think either the check valve or oil pressure relief valve is getting stuck

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[lostranger]

I stops ticking after a minute or two

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