I have a similar problem. On a cold start, the gauge will read zero. If I turn it off and right back on, it appears to work fine. When I took it in, they said the 2005 2.4L shows a 3-wire sending unit. Mine has 1-wire. It appears to be the original motor but I know it was wrecked before we bought it. When the wire is disconnected, the gauge still shows normal. Shop is baffled but they're just a tire shop that looked at it for free.
No oil pressure on gauge?
- Thread starter TJ_GG
- Start date
if you have zero oil pressure you will hear noise from the lifters. Anyone living where the temperature hits -40 can attaest to the fact this occurs every cold start if the engine block heater was not working and lasts 30 or 40 seconds till the oil starts to move and the gauge registers pressure. If the gauge says zero but you have no extra noises from the motor odds are it is a gauge/sender problem. Not a lack of oil pressure.
Oil pressure is fine, sending unit is fine. How many wires are there supposed to be?
And here is the feedback. Today pull off the highway for gas. Idle... waiting to move to the pump.... 0 oil pressure, "check gauges" in RED caps, and a freaking alarm which sounds like I'm in the ICU cardiac ward. Shut it off.... check, check, check.... everything "looks OK". start it... pull up to the pump... fill. Leave for the highway.... All good for 200miles. Into Calgary, stop light, oil pressure gauge drops to 0. rev a bit pressure comes up..
I'm booked into the local Jeep Dealer 8am tomorrow. No lifter noise or any other obscene sounds from the motor.
I'm booked into the local Jeep Dealer 8am tomorrow. No lifter noise or any other obscene sounds from the motor.
That happened on my '97 within a month or two buying it brand new... it was nothing, just a bad oil pressure sender. It freaked me out since I was literally 50 miles from nowhere out in the middle of the desert on a deserted road driving towards Lake Mead AZ.
sgtjdgelinas
TJ Enthusiast
Probably the same thing, bad sender, had the same issue on a 2000 XJ. Oil pressure showed over 60, tried MMO, changed the oil, even dropped the pan and cleaned the pickup. Once I changed the pressure sensor it ran at 40 again.
The gauge read zero at idle, normal at 1500rpm.
So the dealer tested with a mechanical gauge, all OK.
They replaced the pressure switch, all good now. A $40.00 Mopar part.
So the dealer tested with a mechanical gauge, all OK.
They replaced the pressure switch, all good now. A $40.00 Mopar part.
NovaTJ
Member
I recently changed the oil pressure sending unit on my TJ due to low pressure readings when hot, and slow to respond on cold start-up. Used the Mopar unit and real happy with the results. On a durability note with regard to running an engine with no oil in it...I work for Ford as a mechanic...remember the Obama cash for clunkers? We were required to drain the oil and run the engines till they locked up on all turn-ins. The Jeep 4.0L was one of the toughest engines out there! I hated to do it, but we would get these turn-in Wranglers and Cherokee's (mostly rust buckets), and they would be given to me to destroy the engines. I drained all oil, added a silica additive to the pan (which acts like concrete once heated and cured), started the engine and held the gas pedal to the floor. Some 4.0L's took twenty minutes to lock-up or longer, whereas most other brand engines less than a minute!
94c2500
TJ Enthusiast
Sad to hear of 4.0's being trashed intentionally, but those were the rules I guess.
I'll bet they ran until the piston skirts came apart...
So new update.... the new sender did not help. Periodic loss of oil pressure when coming off the highway and stopping for gas, red light etc. Dealership says oil pump.... $1K. ... to pull the engine and change the pump... maybe do the rear main and front seals too $$$ .... OR buy a new engine from SandJ Rebuilders in Spokane, $1811.00 with a 7 year warranty. Get it installed at TuneTech in Spokane. And new clutch, new water pump, new rad, new hoses... and get rid of a leaky, tired 200K mile engine which pulled a 2K pound trailer for at least 30K of those miles. Done deal, good for another 12 years. Why piss around with nickel and dime repairs when a good rebuild fixes it all. This is my 3rd engine from SandJ. First 4.0L.
The engine doesn't have to come out to install a new oil pump. At most you have to support the Jeep by its frame via jackstands and get the axle drooped far enough for everything to clear after unbolting the exhaust pipe. Don't get tempted by a high-flow oil pump, they don't fit with the factory oil pan.
But before doing that I'd make sure it's not just an electrical problem with the oil pressure sender or it's connector, or that you just weren't given a bad or incorrect sender. I was given two bad senders in a row by Autozone, both with different problems, before the third sender finally got things working again on my son's Grand Cherokee.
But before doing that I'd make sure it's not just an electrical problem with the oil pressure sender or it's connector, or that you just weren't given a bad or incorrect sender. I was given two bad senders in a row by Autozone, both with different problems, before the third sender finally got things working again on my son's Grand Cherokee.
Well new engine is in. 500 miles on it so far and I'm happy with the choice. Nice to have a tight engine again with all new parts and a 7 year warranty. I'm not sure why the dealership quoted $1K for installing a pump but why put a pump in an old engine. Really nice to not have a leaky rear mail seal, front seal or valve cover for a while too.
KMarks
New Member
Mine is a 2005 Rubicon 4.0L. Same issue.. cold start, oil pressure gauge reads zero. Then, shortly after, the 'check gauges' indicator pops up. I shut it off, restart, and it seems to work normally. This went on for a few days. After finding the extremely helpful posts here, I decided to replace the oil sending unit. Why not, it's an easy/quick first attempt to resolve. After doing so, the problem went away. BTW, I also followed the advice of some of those here who recommended replacing it with a genuine Mopar part. It cost a little more, but figured.. why risk it malfunctioning again just to save a few bucks. Oh.. i also bought the deep socket to get it on and off. I highly recommend it. It's a good idea versus knuckle busting it off. Laying down on a creeper was able to get easy access from underneath - passenger side. Also, be careful to not bump the starter (very close to the oil sender) while performing the job, I accidentally bumped the positive connector on the starter with the socket wrench and threw a few sparks. OOps.. I guess you could disconnect the battery to be safe. i'm just lazy-stupid
Also, mine was a single wire connector. Just one wire coming off the plug that attaches to the sender.
I ordered the sender and socket from Amazon. Showed up in 2-days. A little pricey w/shipping versus maybe walking into an auto part store, if you can get it there. Plus, if for some reason it doesn't work, you can just take it back. But.. mine came quick and worked.
Mopar W0133-1878744-MPR Engine Oil Pressure Sender Switch $36
Lisle 13250 Oil Pressure Switch Socket $10
This info is awesome! Thank you! I never knew that was a thing. I just pressure washed my engine bay and the oil pressure gauge started reading 0. I knew I had oil, so on to the sending unit.
Update: Nothing was wrong with the sending unit, I must have knocked the plug loose with the pressure washer. Cleaned it up, installed and good to go.
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1998 Sport. Mine loss pressure and I'll on my fifth pressure switch. Last one for Mopar dealership in Dallas. Jumps pass forty and stays there. I give up. Everybody tells me this is the one. It's the only time I could not get the part that was right. Life is too short.