Oil Pressure Hits Zero And Stays There- JGC '96

CHECK GAUGES: Zero Oil Pressure reading-

First had this problem on my way back home, I stuck in traffic, in the middle of the summer. It was a hot day, and I had been driving for 40 minutes. I was at 4,000miles with my oil, which is 5 part synthetic,

1 part Lucas.

I told my mechanic that I though the problem might have to so with dirty oil, because I'd never let the oil go for that long and I'd never had this problem before

Mechanic changed the oil and the sensor. Nothing Happened. The light would come on after the car warmed up for a while. Replaced the Oil Pump- No Dirt in the screen. No change except for higher pressure on Start-Up. Used to be 40-45, now is 50-60.

The problem used to happen after 20 minutes. Now it happens within5 minutes. In addition, the pressure used to go back up with acceleration, but when it hits Zero, it stays there.

The mechanics first suggestion was to pull the valve covers, and replace them, after cleaning out the RETURNS. Now he says he wants to have the CPU reset first, but that costs $100 and may not solve the problem.

What's the deal?

Reply to
NJPainter
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Reply to
RoyJ

There is no engine knocking et al, so we think the oil pressure is fine.

My mechanic told me it shouldn't be the oil pressure relief valve but he never tested it. I've seen the dropping of the pan performed, by my back-up mechanic who replaced the oil pump, but did nothing else.

Are you saying that the valve cover/gasket and the cleaning of the "RETURNS" wouldn't fix this? Should I cancel the $100 appt with the dealer to reset the CPU, or just let them find out what the real problem is, and bring it back to my mechanic to do the work. I have a good mechanic but he's can't figure out the problem or he's too lazy too. I do trust him to do the work though. He changed out my exhaust manifold before.

This whole ordeal, along with countless other bigger issues I've had with cars have made me want to become a mechanic but as for now I can't do anything but change the oil.

Reply to
NJPainter

If you are sure the oil pressure is fine then it is most likely a problem with the gauge or sender or circuits. You did not mention checking the gauge itself and the wiring.

NJPa> There is no engine knocking et al, so we think the oil pressure is > fine.

Reply to
nrs

Thanks...

I guess what I'm trying to say is that there is an accurate reading at start-up. The reading is consistent until the car really warms up. At Start-up the pressure is higher than before, which tells me that changing the oil pump was a good idea, and beyond that, the sensor is getting an accurate reading. Why the oil pressure would bottom out after warming really confuses me. After the problem was recognized it would take 20-30 minutes for the pressure go to zero but now it happens in a shorter time span. Whatever problem there is seems to be getting worse with time.

The car seems to run fine, I've taken it on regular commutes and I still don't hear any loud noises, but I do think that once it's warm and hits zero, that I have less power and acceleration.

Would changing the valve covers/gasket and cleaning out the returns be a remedy. I just seems to be that some sludge or crap is stuck somewhere I really don't think it's a CPU issue, because I'd assume I'd have a bad reading at all times.

Reply to
NJPainter

If you restart the car when already warm, does it give a good reading for a while? If so it would seem it is not a temperature problem but a mechanical problem If not, then it seems it would be an electrical problem, something getting affected by temperature.

As RoyJ suggested, a mechanical gauge would tell you if the oil pressure is actually dropping. If it is not then it is an electrical problem.

A can't see how changing the valve cover gasket could help.

NJPa> > If you are sure the oil pressure is fine then it is most likely a

Reply to
nrs

THe Valve cover and gasket is just because it needs it.

He said he was going to clean out the "Returns". I've heard of this before.

Yes, when I restart it, after warm, the pressure goes to zero.

Reply to
NJPainter

If the returns are plugged with sludge, then it could keep the oil from returning to the pan and cause the low pressure reading. I have seen the returns plug up on a few engines, but it is normally caused from severe neglect of oil changes, coupled with lots of short trips that prevent the engine from reaching operating temperature. I agree with the others, put a mechanical gage on it first, and see what you get. It is possible that the sending unit craps out when hot, or there is some other temperature related electrical failure happening. I'm sure the gage will be cheaper than the cleaning job from your mechanic.

Chris

Reply to
c

Probably an electrical problem because commuting regularly with zero oil pressure would have already destroyed your engine.

NJPa> THe Valve cover and gasket is just because it needs it.

Reply to
nrs

Perhaps I missed something..

Did the mechanic, or the back up mechanic, ever put a mechanical pressure gauge on the engine or are you relying on the dash gauge?

Reply to
billy ray

I'm not a fan of oil additives like lucas (or any additives in fact). Lucas makes the oil tend to cling to parts, which in turn robs it from the oil sump. It can also cause it to stick to the engine walls and bake, forming sludge. Not sure how well it works though a filter. Generally the consensus is, if it was good for the engine the oil vendors would already have it in the mix.

Do the mechanical gauge. Also check the oil pressure senders return wire for kinks/burns/chafe. 0psi is

Reply to
DougW

The 'deal' is your 'mechanic' is ripping you off blind!

He is 'totally' incompetent and show this by changing bullshit parts without testing the oil pressure with a real gauge.

You should have a good case for small claims court. Bullshit rip off artists like that shouldn't be allowed to stay in business.

He gives a whole new meaning to the word $tealership.

It is more than obviously an electrical fault seeing as the engine keeps on running with the supposedly zero oil pressure. When the oil pressure 'really' drops to zero, the engine will start making bad valve noises within seconds or minutes at the most.

And 'no' cleaning the 'returns' is only his way of suckering you for more cash. The only thing he wants to clean is your wallet!

It is also 'super' easy to clear the CPU codes... Just disconnect the battery for a few minutes.... There are also auto store places that will check the codes for free.

You can get a mechanical gauge and screw it in yourself or you should find a 'real' mechanic, not the thief you have.

I was serious about bringing him to court too. The local newspapers might like the story too.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06
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Reply to
Mike Romain

No they didn't do the mechanical gauge.

Reply to
NJPainter

First off,THANKS TO EVERYONE THAT HAS REPLIED!... I regret not stopping here first, everyone's been helpful.

Problem is, I have no idea to do any of these things. My mechanic is probably being lazy- so I guess the Jeep dealer will find the problem tomorrow morning... it stinks...

My mechanic is down the street from me so it's really convenient. He's usually fair with his price, and has done the exhaust manifold for me and cat-back exhaust. At this point I'm annoyed that he didn't figure out the problem but what am I gonna do? I don't have the tools to do any of this.

The reason why I think it's a physical thing is because I let the oil go too long. That's why I think cleaning the returns would work. If that's the case the mechanic won't charge me much, he know he didn't do his due diligence. He just put the new sensor on and thought that it would be fixed.

Anyone have any tips on dealing with a dealership mechanic? I don't want to get a $200 bill for diagnostics and then have them tell me it's another amount of money to fix the problem...

Reply to
NJPainter

Neither did any of us till we started learning. :)

It's not rocket science. Start simple and work your way up or dive in and get the t-shirt. I started by simply rotating tires, did shocks, replaced spark plugs and other fiddly bits. Eventually I tried my hand at rebuilding a carurator, twice. Now I'm up to the point where installing a stroker kit sounds like fun. (sick isn't it.) :) But each time I do something the money saved pays for more tools.

The dealership mechanic will have a set charge for diagnostics and usually apply that against any labor/part charge for fixing the problem. Thing is dealerships aren't cheap places to get labor done. But sometimes they are the only place to turn.

Reply to
DougW

thanks for the advice and the inspiration...

I'm a little scared about going to the dealership. I won't be able to negotiate price, so I hope I get a cool mechanic to work with. I hope it's something small, but I'll probably back on here tomorrow crying about how much I just spent.

How do you do your own work without a lift?

Reply to
NJPainter

Not everything requires a lift. I use a 3ton floor jack and heavy duty jack stands when there isn't enough room to slide under the jeep. The biggest problem I run into is stuck bolts, but even then there are ways around that.

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That was one way to loosen a stuck axle bolt. Not graceful, but it works. :) I need to buy an air wrench.

Reply to
DougW

You can rent, often for free, a mechanical oil pressure gauge from many auto-parts stores. It is simple to attach, you remove the oil pressure sender with a wrench and screw in the mechanical gauge and you read the actual pressure directly.

From your post I think that this oil change was delayed to 4000 miles. This is more than the 3k interval that will give you maximum engine life but less than the warranty requirement.

Upon getting an zero pressure reading off a dashboard gauge you mechanic's first step should have been checking the actual pressure with a mechanical gauge.

This is not a 'Jeep thing' this would hold true of any engine that uses electrical senders (most if not all).

We all started somewhere, if the mechanical gauge shows proper pressure then the sender or wiring is at fault. This would not be the first or last sender that was defective new from the box.

If, in fact, your pressure falls off then you have valuable information to give your new mechanic.

Most vehicle maintenance can be done without a lift. Sometimes you need a set of ramps or jack stands but they can be obtained at any auto parts store as well as K-Mart, Wall-Mart, Sears, etc.

A basic tool set is not expensive and any tool you buy will be paid for the first time you use it. Do not buy poor quality or made in Red China tools. Specialty tools, such as this mechanical oil pressure gauge, can be rented at many auto-parts stores... just ask. The worse thing they could do for asking is castrate or kill you.... they won't harm your Jeep or anything serious.

A good reference manual is always helpful when you start... The best manual is the Factory Service Manual specific to your make and model. They can often be obtained second hand on eBay in both paper and CD format.

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Reply to
billy ray
4000 miles isn't really that long, and it's not NEARLY enough to cause the kind of problem you are having. If you regularly drove it 10,000 miles or more between oil changes then you could have this problem, but not one 4,000 interval.

Jeff DeWitt

NJPa> First off,THANKS TO EVERYONE THAT HAS REPLIED!... I regret not

Reply to
Jeffrey DeWitt

In article , Mike Romain wrote: #It is more than obviously an electrical fault seeing as the engine keeps #on running with the supposedly zero oil pressure. When the oil pressure #'really' drops to zero, the engine will start making bad valve noises #within seconds or minutes at the most. I agree with Mike on this. When my '99 WJ had a like issue, I took it back to the dealership multiple times under warrenty, but as luck would have it, it always "fixed" itself when in the shop. The dealer finaly was able to catch it zero'ed out and traced the fault to a bad electrical line. Had to run a bypass wire.

#It is also 'super' easy to clear the CPU codes... Just disconnect the #battery for a few minutes.... There are also auto store places that #will check the codes for free. Checking them should just be a matter of turn the ignition on, off, on, off, on without cranking...

/herb

Reply to
Herb Leong

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