jeep oil pressure-help!

[bear4work]

i know this is off topic, but i have a 1990 Jeep Cherokee with the 4.0L 6-cyl motor. I just happened to glance down at the oil pressure gauge while i had just started it up and it was at zero. absolutely no movement of the gauge. I had never noticed this before, the engine started fine and sounded normal, there wasn't any strange noises. I quickly shut it down as to not harm the engine. The oil level was a bit low but I filled it and still no pressure. I have no other way of testing the pressure. could it be a faulty gauge or sensor or is my pump gone? the engine only has around 90k on it. Is anyone familiar with this or had the same problem? Thanks, i really need help.

[Bigdog]

I wouldn't run it until you can verify the pressure. A failed pump is just as likely as a failed indicator.

[FCUBMAN]

Sounds like a failed sensor. Beg, borrow, or buy another one and try it. I have had bad sensors do this on a couple of vehicles.

[Barnyard]

On a jeep, if you have no strange noises and it runs fine your pump should be working. I would try checking the sending unit and any related wires or hoses depending on whether you have a guage or idiot light. If the pump is not turning you would get rattling pretty quick on the 4.0 L motor.

I believe the pump is driven off the bottom of the distributor on that model like the Chevrolets. You could pull the distributor to see if the bottom ear that drives the pump is broken off. But if it is you should have a lot of noise by now.

I would try the sending unit first.

[spiveyman]

I thuoght I posted last night.....this connection is weird. I was saying that my old Bronco i had always did that. the motor ran fine, but the pressure gauge, and one or two others i remember, would randomly shutoff when i was going down the road. I eventually found out it was bad connection of some sort, never paid it any attention after that. Dont mean to say this is your problem, but like some others are saying it might be something to check out! probably cheaper than a pump. Do some investigating!

[Hengy]

I had a 1993 Mercury Capri (Australian) that did that. Started up and the Oil Pressure was GREAT, but when it warmed up, the pressure dropped. Found out that it was the grounds in my engine compartment that were corroded and not giving a good connection.

Once I took off the grounds and cleaned them good...slick as a whistle! (worked great!)

Wonder where I have heard people talking about good grounds before...hmmm...where could it be??

[junkman1946]

Just did a replacement on one of those 4.0 It has electrical sending unit for oil pressure- prone to failure. Take off the valve cover start the engine- if oil comes up to the rockers within 10 seconds- you have oil pressure. Dont race the engine run as low RPM as possible.

[bear4work]

thanks for the help, i checked and i do have oil pressure, so it must be a failed sensor.

[Hengy]

Make sure that the grounds are clean first and see if you get a reading on the sensor first before spending the money on a new one!! Don't ask how I know!!!

[spiveyman]

Good to hear you're making headway. Yes, whlie you're in there you might outta take a brush and clean the corrosion off any connections. they can be a PITA sometimes