Check oil pressure light in cab

sidewayskj · **Posted:** Thu Nov 16, 2006 1:09 am

For the past little while my stupid check oil pressure light has been coming on once and a blue moon, only while I am sitting at an idle. It doesn't come on when I'm driving or anything just an idle and not all the time maybe one day out of the month maybe. I changed the oil early thinking maybe that would help and filter. I am using 10W-30 pennzoil reg oil. Have done oil changes every 5000kms. It doesn't come on every day just once and a blue moon, and only while I am idle as soon as I give it a little gas light goes away and then when it comes down to an idle light is on again. Do some driving like today and the light is gone for the rest of the day. Wondering if any of u guys are experiencing this and wondering also what weight the owners manual says to use if that even matters. Thanks for your time. My liberty is an 02 3.7L gas pod

detroit_doc · **Posted:** Thu Nov 16, 2006 12:21 pm

It's hard to say. How many miles do you have?

Basically think of all the oil passages through your engine as a long pipe. At the beginning of this pipe is your oil pump. Along the pipe is a series of controlled leaks where oil is allowed to go to lubricate things like your crankshaft. There is also a oil control valve at the end of the pipe designed to bleed off excessive pressure. Your oil pump pressurizes this long pipe. The ability of your oil pump to maintain pressure is proportional to engine speed.

If you're lucky it is something like a worn out or improperly working oil control valve that is sticking open. If you are unlucky your crankshaft bearing are toast causing too much oil to flow.

Unless you are experienced, this might be a good one to let a pro diagnose.

I believe my manual calls for 5w30 oil. If you are running 10w30 now, going to 5w30 will make the problem worse.

crash87 · **Posted:** Thu Nov 16, 2006 12:48 pm

I had this exact same problem, my friend said he read somewhere about jeep not wiring the kj properly and suggested replacing the battery as it was cracked and needed replaced anyway, after replaceing the battery it has gone away, seeing as yours is an 02 like mine, and you still probably have the stock battery I would look into replacing it before doing all the expensive mechanical work.

sidewayskj · **Posted:** Thu Nov 16, 2006 11:40 pm

Yea the replacing the battery is a good idea. I think that nothing is really wrong because of it only being there once and a blue moon. So for the crankshaft idea I think that is a little to expensive to go that route and if it is only happening once a month or less then I think it maybe would be the battery. I might just try unplugging the connections and cleaning them up, and connecting them back on to see if it woud reset the comp on the jeep. Thanks for the suggestions the two of them I wish this were a more common problem like the radiator bomb I got. It is an 02 jeep 3.7L 100km

Jeepjeepster · **Posted:** Sat Nov 18, 2006 12:50 pm

detroit_doc wrote:

It's hard to say. How many miles do you have?

Basically think of all the oil passages through your engine as a long pipe. At the beginning of this pipe is your oil pump. Along the pipe is a series of controlled leaks where oil is allowed to go to lubricate things like your crankshaft. There is also a oil control valve at the end of the pipe designed to bleed off excessive pressure. Your oil pump pressurizes this long pipe. The ability of your oil pump to maintain pressure is proportional to engine speed.

If you're lucky it is something like a worn out or improperly working oil control valve that is sticking open. If you are unlucky your crankshaft bearing are toast causing too much oil to flow.

Unless you are experienced, this might be a good one to let a pro diagnose.

I believe my manual calls for 5w30 oil. If you are running 10w30 now, going to 5w30 will make the problem worse.

How do you figure that? 5w-30 is thinner than 10w30 so it would flow better.

Could just be a bad sensor. thats why I hate lights and not having guages.. They had to take them out b/c soccer moms were scared when the thing moved alot. :roll:

sidewayskj · **Posted:** Sat Nov 18, 2006 12:58 pm

darn soccer moms wreaking the libby oh well.

detroit_doc · **Posted:** Sun Nov 19, 2006 11:53 pm

Jeepjeepster wrote:

How do you figure that? 5w-30 is thinner than 10w30 so it would flow better.

If you oil pump is unable to keep the system pressurized with a higher viscosity oil (10w30) the problem will be worse with a lower viscosity oil (5w30).

For example, let's say his problem is the bearings. Too much clearance due to bearing wear or damage allows more oil to flow past them than normal. This additional flow past the bearings reduces the oil pressure. Now if you reduce oil viscosity (i.e. switch from 10w30 to 5w30) even more oil will flow past the bearings reducing the oil system pressure even more.

sidewayskj · **Posted:** Mon Nov 20, 2006 3:38 pm

guys the problem is like a once a month light pop up not every day. If it was every day I would be freaking but it is like seriously once in a blue moon. If something was wrong with the crank shaft it would show up all the time or possibly make a little noise. I think it is just a computer glitch am I correct or no??

detroit_doc · **Posted:** Tue Nov 21, 2006 11:39 am

No it's not a computer glitch. Oil pressure lights come on because the oil pressure is low. That's what they do. Do you think it's a computer glitch when your low fuel light comes on too?

The most likely culprits are

1) Your truck isn't running well. If it almost stalls at idle, the RPM will drop low enough that the oil pump can't keep up and the oil light will come on. If you truck is running rough at idle when the light comes on then that's probably it. This happens after I reset my computer. The truck wants to stall when I first drive it and the oil light will come on when it almost stalls.

2) Your oil control valve is occasionally sticking partially open. Then you start driving again, it pushes on the valve un-sticking it and you don't see it again for a month until it happens to stick again.

3) You have excessive engine wear. This wear puts your oil pressure just above the threshold to turn the light on. You occasionally get your oil warm enough that it's viscosity drops to the point just under the threshold to turn the light on. You drive for a bit, cool your oil a bit, and the light goes off.

4) You have a faulty oil pressure sending unit. I've never replaced one on a KJ, but this probably should be easy and cheap. It might be worth a try.

crash87 · **Posted:** Tue Nov 21, 2006 12:21 pm

seriously check your battery, i had the exact same problem, changed out the battery and no more random oil pressure light, if your still using the original battery it wouldnt hurt to replace it anyway.

detroit_doc · **Posted:** Tue Nov 21, 2006 12:34 pm

crash87 wrote:

seriously check your battery, i had the exact same problem, changed out the battery and no more random oil pressure light, if your still using the original battery it wouldnt hurt to replace it anyway.

I have no clue why a bad battery would make your oil pressure light come on. Are you sure it wasn't the charging light you were seeing?

crash87 · **Posted:** Tue Nov 21, 2006 12:51 pm

detroit_doc wrote:

crash87 wrote:

seriously check your battery, i had the exact same problem, changed out the battery and no more random oil pressure light, if your still using the original battery it wouldnt hurt to replace it anyway.

I have no clue why a bad battery would make your oil pressure light come on. Are you sure it wasn't the charging light you were seeing?

Im positive it wasnt the charging light, at idle on a cold day the oil pressure light would occasionaly come on then go off if I where to start moving or raise RPMs much like sidwayskj described earlier, went to a friends garage to hunt down the cause, oil pressure was normal, idle was normal nothing was wrong, noticed that battery terminals were heavily corroded so we cleaned them off, while doing so we noticed there was a slight crack on the battery, gave the battery a load test which it failed miserabley, so we replaced the batter about 2 months ago and the light hasnt came on since in conditions it consistantly did last year and began to this year. It may not be the cause for his problem, but I thought I should post my experience before he begins tearing into his motor.

sidewayskj · **Posted:** Fri Nov 24, 2006 2:49 am

I just figure it wasn't something to do with engine wear. I am nice to my kj and don't bag the hell out of it and if the 3.7L can't go 100 000km on a motor than the jeep is garbage. I will go back to toyota if that is the case 300 000km on orginal trans and motor sold it to a guy all is still well. If it is motor this will be the last DC product I will every buy for the rest of my life. So in terms I would say his battery idea is on the money and the corrosion on the positive side on my battery is looking nasty going to clean it off and inspect the battery. Not to offend anyone and I know the risk I take in thinking it isn't motor but who on here has blown a motor up at 100 000km.

sp33doe · **Joined:** Tue Jul 12, 2005 10:34 pm **Posts:** 17

hi to all

your problem might be your OIL PRESSURE SENDING UNIT mine has done it, thought it was

my oil pump going bad but its just the sending unit. They fix it under warranty

sending unit cost like $20 under (canadian mony)

hope this helps you

sp33doe[/u]

sidewayskj · **Posted:** Sat Nov 25, 2006 12:37 am

I will try that after cleaning my battery posts thanks for the tip

BlackLibertyCRD · **Posted:** Sat Nov 25, 2006 12:52 am

oh yeah, finally on the right path. I bet oil pressure sender unit. :mrgreen:

Check oil pressure light in cab

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