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Old 02-11-2009, 06:10 PM   #1
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New 4.0L concerns

I just bought a 97 jeep with the 4.0. It's really rough at idle but that's not my main concern. Randomly when i crank it up, my gauge cluster shows no oil pressure. As soon as i start driving the oil pressure will go up and seem normal.

I know the 4.0 has low oil pressure at idle, but right now at start-up it shows no oil pressure and the light stating check gauges comes on when this happens. Does this mean the oil pump could be going bad or does anyone know why it would have this problem. Theres only about 70,000 miles on the motor.

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Old 02-11-2009, 06:16 PM   #2
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I would check the oil pressure sending unit. IF your not getting any oil pumped your going to hear a lot of metal on metal contact. I know from a fact when I lost my motor in my stang it was because of the oil pump failing and well locked my motor up going 85 mph down the highway in Socal long day that was. Check your sending unit.

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Old 02-11-2009, 06:20 PM   #3
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It could be as simple as a dirty or bad oil sending unit but it could be as major as the oil pump also.Hard to say short of slapping a pressure gauge on it.The check gauges light will come on anytime the gauges do not read.Does the engine make any noises like pecking or rattling when this happens?I would start by replacing the sending unit if the engine isn't rattling.You could also put an aftermarket oil pressure gauge in.
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Old 02-11-2009, 06:34 PM   #4
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It could be as simple as a dirty or bad oil sending unit but it could be as major as the oil pump also.Hard to say short of slapping a pressure gauge on it.The check gauges light will come on anytime the gauges do not read.Does the engine make any noises like pecking or rattling when this happens?I would start by replacing the sending unit if the engine isn't rattling.You could also put an aftermarket oil pressure gauge in.

It doesn't make any noises like metal on metal, it sounds just fine. i thought about the sending unit, but if you rev it up at start up then the pressure spikes like it should. and as you drive it the oil pressure reads normal. It's only randomly at start-up which it what has me worried. i was thinking if it was the sending unit, then it would have trouble reading at all times, not only on start-up
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Old 02-11-2009, 06:37 PM   #5
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make sure you are up on your maintenance, change the oil regularly. i would replace the sender because of how common a failure it is. it also doesn't hurt to put some oil flush chemcial in it, run for 5 mins and change the oil. i never used to think much of that stuff, untill i saw it really do its job.
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Old 02-11-2009, 06:52 PM   #6
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make sure you are up on your maintenance, change the oil regularly. i would replace the sender because of how common a failure it is. it also doesn't hurt to put some oil flush chemcial in it, run for 5 mins and change the oil. i never used to think much of that stuff, untill i saw it really do its job.

How would i go about changing the sending unit?
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Old 02-11-2009, 07:10 PM   #7
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it is very easy, it is right next to the oil filter, and often gets damaged with filter changes. there is a special socket to remove it, but thats not very expensive. remove the wiring connector, and put the socket on the sender, and the whole thing turns out of the block. takes 10 mins, put a pan under it cuz you will probably loose a little oil in the process.
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Old 02-11-2009, 07:13 PM   #8
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If you are replacing it with a 6.0L I wouldn't worry.
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Old 02-11-2009, 07:14 PM   #9
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If you are replacing it with a 6.0L I wouldn't worry.
way to beat up on a new guy az,
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Old 02-11-2009, 07:41 PM   #10
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way to beat up on a new guy az,

It's happens when your a newbie to a different forum. i would expect nothing less
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Old 02-11-2009, 07:56 PM   #11
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It's happens when your a newbie to a different forum. i would expect nothing less
we're a nice big family here. no one ever really anyone. so blast him back already

oh yeah, i wanna see pics of that 6.0 install

oh yeah, rough idle. clean the throttle body, 4.0's need to have that kept up on, then make sure your state of tune is good. cap rotor plugs wires and so on.
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Old 02-11-2009, 09:28 PM   #12
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we're a nice big family here. no one ever really anyone. so blast him back already
Go a head, make fun of my Teal Jeep like everyone else.

And it looks like 'Doc has you pretty much set on info for your task.
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Old 02-11-2009, 09:38 PM   #13
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Go a head, make fun of my Teal Jeep like everyone else.

And it looks like 'Doc has you pretty much set on info for your task.
Yeah, the TB, plugs and wires i was hopefully gonna get into this weekend. I've also got to change the steering stabilizer as it feels like the beginning of the DW. i guess that's expected when you buy the vehicle off of a repo lot.


Hopefully the oil pressure problem is as easy as the sensor.


The sad part is, up until now i had now idea what he was talking about with the 6.0L. i just now saw it in the thread title. it's a mix of i-6 and 4.0. it's my new special engine i created after along night of drinking and playing with a cutting torch. (maybe that explains the pressure problem)

smart @$$es...
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Old 02-11-2009, 09:43 PM   #14
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don't forget the cap and rotor, you were probably just skipping them for typing sake, but don't skip on those.

do some searching on dw, it is basically never the steering stabilizer, tons of possibilties, but look at your track bar first, and then read up, lots of good info here on it.

lets see some pics of this new motor of yours. alcohol and a torch can cause pressure problems.
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Old 02-11-2009, 09:53 PM   #15
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Go a head, make fun of my Teal Jeep like everyone else.
You know I was just kidding right?

After I got my jeep my friends informed (over and over) that yellow is ghey............ I had no idea, but no one ever hit on me?
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Old 05-29-2012, 11:14 PM   #16
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Anyone ever heard of the center of an Oil Sending Unit being blown out
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Old 05-29-2012, 11:28 PM   #17
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I had the same oil pressure problem, changed the sending unit and everything is good. I did not use a special tool.

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