Why does my oil pressure gage go down to zero when idling?

Question

Oil level is full. 1999 Jeep Grand Cherokee. Just had oil changed last week.

Answer 1

Probably a very weak oil pump or something wrong with the filter. I would get it to garage before it scatters along a high road somewhere. Could be a faulty guage or pressure sending unit, but I would want to know.

Answer 2

A couple of questions for you... Did it read normal before the oil change and did they (you) use the same viscosity oil as you had before? Does it read normal at higher RPM's? Thin or diluted oil will cause a low reading. BUT Unless you have run the motor low on oil (or it has many many miles on it) it is likely the sending unit. Have the pressure checked with a mechanical gauge. If the gauge is reading corrrect then you may have very thin and diluted oil OR have bad main bearings. A clogged pickup screen usually shows up at higher RPM's so likely that is not it. I have a stock 1950 dodge car with a "soft crank" that reads zero at idle and has for 30 years. The motor is still getting oil but your main bearing clearance sets the pressure reading. Worn bearings (or in my case the crank) will allow the gauge to read low because there is excess oil flow from the bearing areas. I overhauled a small block chevy that the owner demanded very tight clearances and the gauge would read over 100 PSI on startup and carry 65-70 at idle. Clearance was extremely tight on that one.

Answer 3

Ouch! Be very careful when driving the vehicle indicating low oil pressure. The reasons for low oil pressure could be: low fluid level, weak oil pump, clogged oil passages, weak engine bearings, and bad oil pressure sending unit. Check for pressure by renting an oil pressure gauge at autozone. Remove the oil pressure switch/sending unit and install the gauge rented at autozone. Fire the engine and verify the pressure. Change the sending unit and flush the engine If there's pressure. If there's no pressure you have these options, replace the oil pump, and oil pump drive rod, or buy a rebuilt engine with a new oil pump in it.

Answer 4

quite common for it to go low, but not zero. Zero would mean no oil flowing and your engine would last about 2 minutes. Oil pressure guages are not the most accurate things, its probably not zero.

So long as it picks up promptly at 1200 RPM, and it high when cold, you're fine.

Perhaps you've put a thinner oil in it this time.

Answer 5

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Answer 6

Get below the hood and locate the oil stick. Pull it out and wipe it off. Push it each and each of ways down into the crankcase. If no longer something shows, you have an oil leak and are out of oil. look below your vehicle. How plenty oil is on the floor? If the oil in the pan is nice, then something is misguided inclusive of your gauge. in case you could no longer restoration it via including oil, you could desire to work out a mechanic.

Answer 7

I have a Cherokee, but have never had your problem. If the gauge was ok before you had the oil changed ..Take it back to the garage, and explain it to them ! It must be an electrical problem...

Answer 8

did you check your oil is it low ? did this do that before you took it in ? i would put a little thicker oil in it if this is the problem, 10w40 or some additives its about all you con do inless you want to rebuild it .make sure your gauge is accurate, put a gauge in temporary right off your pressure port and see if it was the same as what your other one was reading.

Answer 9

I think it means that there is very little oil pressure whilst you are idling.

Answer 10

I just had this problem. your oil pump is about to go. better get it in the shop now or you will be stranded.