sptownsend999

Two months ago, I bought a '94 Country (AW4) with about 150k miles on the 4.0. The other day, I noticed the oil gauge was indicating about 20-25 lbs at 1400 rpm, in top gear. The thing is, I can't remember specifically taking a reading off the oil gauge in the last two months, so I don't remember if it was like this when I test drove it. I know that spec says "no less than 13 lbs at a 600 rpm idle and 37-60 above 2000 rpm", and I'm familiar with the old school "every 1000 rpm should have 10 lbs". I've observed 50-55 lbs cold start, 15-20 at warm idle (800-ish rpm), 30-40 lbs from 1500-2000 rpm when I'm driving in town and the automatic chooses 2nd or 3rd, but then (like I said), when the transmission shifts into top gear, pressure drops to around 20-25 lbs at 1400-ish rpm (that's usually going about 40 mph).

My question is: how low is low enough to justify mechanically tearing into my daily? I've inspected the oil pressure sensor and the oil pressure gauge; both are in good working order. Given those symptoms, how long can I put off an oil pump transplant? When should I start worrying??

Thank you!

Spencer

TrailerTrash

Sometimes electronic gauges/sending units can be off. You might have more or less oil pressure then they are indicating.

If you are worried about it, you need to verify the oil pressure with a mechanical gauge. It is very simple to do. Remove the sending unit on the side of the block and install the line for the new gauge/tester. Get the engine up to operating temperature and go for a half hour drive while noting the oil pressure in various driving conditions.

tlc1976

What I would do first is clean and tighten the electrical connector. I’ve had them loosen up and get bad/no readings, and I’ve been told this is pretty common. I used a tiny flat blade screwdriver to tighten the pins/blades in the connector.

tjwalker

Time for a mechanical gauge to verify as mentioned by TrailerTrash. It's easy and it is the only way you'll know for sure. Many parts stores will rent the gauge to you for little or nothing, call around for availability.

Oil pressure sending units are a common failure. And if your pressure is low, I've seen many engines run for many miles with that condition. If you need one, source a genuine MOPAR unit for best accuracy and mating with your factory gauge.

Post your results with the mechanical gauge here for comment. Oftentimes, it is bearing clearances that are the cause of lower oil pressure.

cruiser54

Great advice here^^^^.