Zero Oil Pressure - JeepForum.com
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post #1 of 16 Old 07-19-2013, 01:39 AM Thread Starter
zRoxxah
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Zero Oil Pressure

I don't have any oil pressure, like the title says. Here is what I've done about it.

-Oil change
-Dropped pan
-Oil pickup tube was clear
-Oil pump pulls (power drill tested)
-New oil pressure sending unit
-Oil in the filter

I am stumped on what to do next.


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post #2 of 16 Old 07-19-2013, 02:41 AM
caseyliffick
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New cluster? The physical gauge could have shot craps. Doesn't happen often, but you could snag one from a JY, swap it in in about 30 mins and eliminate a culprit. I've had a gas gauge show zero gas no matter how full the tank. Talk about rolling the dice.
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post #3 of 16 Old 07-19-2013, 03:52 AM
gearheadnick
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Temporarily hook up a mechanical oil pressure gauge in place of the stock sending unit to verify what's actually going on. The dash gauge might not be working like caseyliffick said.

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post #4 of 16 Old 07-19-2013, 04:04 AM Thread Starter
zRoxxah
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I will try that. I also seafoamed two days ago and she hasn't been running since. I think I may have blown a piston ring(s) and have a case of blow-by. I found a dab of oil on the filter when I pulled the cold air box to clean the MAP sensor.

Can blow-by cause zero oil pressure? The gauge will move when I turn the key to on, but only like .5mm above 0 psi.

Matte Black '96 ZJ 4.0
IRO 3.5" Benchmark Lift, Bilstein 5100's, 31x10.5x15 Westlake SL369 A/T's, Moog Super Trail Boss SS, KOR Rad Support, Chopped-up Front Bumper
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post #5 of 16 Old 07-19-2013, 06:08 AM
exmilitary
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I agree with gearheadnick.also check the sending unit it too can be defective.
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post #6 of 16 Old 07-19-2013, 07:34 AM
1ATony
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If the factory gauge isn't reading any oil pressure, it's common for the factory switch to go bad over time. We carry them here if you need a new switch. Jeep Grand Cherokee Oil Pressure Sender

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post #7 of 16 Old 07-19-2013, 07:37 AM
ZeeJay1997
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Pull the oil pressure sensor and run a coat hanger through the passage. Then have someone turn it over while you hold an old towel or something over the oil pressure sender hole.
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post #8 of 16 Old 07-19-2013, 07:49 AM
Uniblurb
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Remove your new oil sending unit and run a pipe cleaner through the hole/port it screws into if you didn't do it beforehand.

The drop of oil on your air filter may be a whole separate problem. Once you get your gauge working if you still see oil coming out there replace the rear CCV valve on the back/top of the valve cover and check the plastic line going to it to make sure it's not clogged. It's evident your crankcase ventilation system may not be working correctly if your seeing oil on the filter. Some type of blow-by could be causing this problem though.
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post #9 of 16 Old 07-19-2013, 08:58 AM
zjosh93
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Quote:
Originally Posted by zRoxxah View Post
I will try that. I also seafoamed two days ago and she hasn't been running since. I think I may have blown a piston ring(s) and have a case of blow-by. I found a dab of oil on the filter when I pulled the cold air box to clean the MAP sensor.

Can blow-by cause zero oil pressure? The gauge will move when I turn the key to on, but only like .5mm above 0 psi.
Blow-by won't affect your oil pressure.

It would be hard to accidentally suck in enough Seafoam to hurt your engine. Even if you managed to get a piston to hydraulic lock it's the rods not the rings that get damaged. I've run a turbo engine through severe detonation enough to scuff the edge of the piston crown and the rings didn't break, blew the moly coating off but didn't break.

The Seafoam may have cleaned off the tops of the pistons enough that you are getting more blow-by but if so your rings were already either gummed up or worn out. I doubt it though.

To check for blow-by just pull the lines to the CCV and air box and cover them with your thumbs while idling. Wait a few seconds and let go, if a bunch of pressure has built up you have blow by. Every engine has some. It means your engine is worn and inefficient but they'll run a long time with some pretty bad blow-by.
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post #10 of 16 Old 07-19-2013, 09:44 AM
1ATony
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Sorry I just noticed that you had tried the sender already.

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post #11 of 16 Old 07-19-2013, 12:01 PM
JohnnyZJ
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are you going through oil at an alarming rate?
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post #12 of 16 Old 07-19-2013, 12:04 PM
PolkaPower
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If you really had no oil pressure you would know it.
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post #13 of 16 Old 07-19-2013, 12:10 PM
Midnightluckey
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Quote:
Originally Posted by PolkaPower
If you really had no oil pressure you would know it.
I'm thinking this. I've heard an engine run at 0 pressure before. It starts sounding like a ford diesel real fast.

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post #14 of 16 Old 07-19-2013, 01:33 PM Thread Starter
zRoxxah
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Will a mechanical gauge work with the engine off...or when the key is in the ON position? I'm also having trouble getting it to start after the Seafoam. I have pulled the spark plugs and put in brand new ones. She started strong then died after idling for 4 minutes. I pulled the brand new spark plugs, they're so new I can only measure their use in time rather than miles...about 6 minutes ha! I had them out in order from 1-6 and I noticed brown residue on one. I was so shocked that I picked it up and didn't take note of it's position so I can't tell which cylinder it was in. I also have my MAP sensor pulled and cleaned it with MAF cleaner. I feel this part is meant to be replaced rather than cleaned since you can't really take it apart like a MAF. Unfortunately I can't pick up a new one since my Jeep fixing budget has ran down.

Quote:
Originally Posted by ZeeJay1997 View Post
Pull the oil pressure sensor and run a coat hanger through the passage. Then have someone turn it over while you hold an old towel or something over the oil pressure sender hole.
Quote:
Originally Posted by zjosh93 View Post
Blow-by won't affect your oil pressure.

It would be hard to accidentally suck in enough Seafoam to hurt your engine. Even if you managed to get a piston to hydraulic lock it's the rods not the rings that get damaged. I've run a turbo engine through severe detonation enough to scuff the edge of the piston crown and the rings didn't break, blew the moly coating off but didn't break.

The Seafoam may have cleaned off the tops of the pistons enough that you are getting more blow-by but if so your rings were already either gummed up or worn out. I doubt it though.

To check for blow-by just pull the lines to the CCV and air box and cover them with your thumbs while idling. Wait a few seconds and let go, if a bunch of pressure has built up you have blow by. Every engine has some. It means your engine is worn and inefficient but they'll run a long time with some pretty bad blow-by.
Can you do what ZeeJay1997 mentioned and test the CCV without having the engine running? I feel like there would be pressure if it's cranking but I'm not sure. She also sounded fine while idling when I actually got her to start. The only ticking I heard was my manifold exhaust leak haha. I consider myself a weekend warrior mechanic at best. I'm learning!

Matte Black '96 ZJ 4.0
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post #15 of 16 Old 07-19-2013, 02:44 PM Thread Starter
zRoxxah
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Also I don't think I burn oil. I do have a leak causes by a gap in the silicone-RTV I put on the oil pan gasket. That's gonna get fixed while my pan is dropped though.

edit:

Here's the picture of that one spark plug! The other 5 are minty fresh looking.




Matte Black '96 ZJ 4.0
IRO 3.5" Benchmark Lift, Bilstein 5100's, 31x10.5x15 Westlake SL369 A/T's, Moog Super Trail Boss SS, KOR Rad Support, Chopped-up Front Bumper
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