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Oil pressure issue

M

MudfrogK5

NAXJA Forum User
Location
Roanoke VA
Working on a 90 Sport w/ 4.0.

Slowly my oil light has been coming on (no oil pressure guage). It's got to the point that it remains on when the engine is cold. This is odd as in my experience usually when the engine warms up the oil light will come on when a pump is failing. So I changed the oil pressure sensor and this had no effect. Does this sound like the oil pump or something else I might not know about on these 4.0's.

It's just very odd to me how the light stays on when the engine is cold but when it warms up it stays off (for the most part, might flicker every once in awhile).

Are the rebuild kits any good for these or would that be a waste of time.

BTW.. Yes I checked my oil level.. I do have a leak which I'm fixing this weekend (valve cover gasket) but the oil is at the correct level.
 
doublestack said:
Does the motor sound like it has low oil pressure? If it is that low you should be getting a lot of engine noise.
Click to expand...

I forgot to mention that. No the engine does not sound unusually loud. I can tell when I'm a quart low from the lifters starting to stick a little. It does not sound like this.
 
If I do break down and buy an oil pump should I go with the high volume (20% more volume). I read a disclaimer to check for clearance, will these fit?
 
3XJFamily said:
Thread in a manual guage and see what it's really running for oil pressure.
Click to expand...

x1000. Why throw parts at a possible non-problem. Test it with a mechanical gauge before you do anything else.

Hell, your problem could be a low idle and the light is coming on because you are just short of a stall, common occurrence on a lot of engines. Auto or stick? If auto, what is your idle in "D", engine and transmission fully warmed up--after about 20 minutes of operation? If a stick, you should have 700-750 rpm in neutral, same for the auto but in "D" as stated above.
 
joe_peters said:
x1000. Why throw parts at a possible non-problem. Test it with a mechanical gauge before you do anything else.

Hell, your problem could be a low idle and the light is coming on because you are just short of a stall, common occurrence on a lot of engines. Auto or stick? If auto, what is your idle in "D", engine and transmission fully warmed up--after about 20 minutes of operation? If a stick, you should have 700-750 rpm in neutral, same for the auto but in "D" as stated above.
Click to expand...

Always stays on.. not just at idle, even at high rpm.. it's a manual but no tach.. just that annoying shift up light in the dash..
 
joe_peters said:
x1000. Why throw parts at a possible non-problem. Test it with a mechanical gauge before you do anything else.
Click to expand...

You can rent a mechanical oil pressure gauge from many parts stores for a few bucks.

Do it and you'll know your real oil pressure. You replaced the sending unit but you could have a gauge problem.

Confirmation of your numbers is essential to your making good decisions. Testing will get you that data.
 
birchlakeXJ said:
You can rent a mechanical oil pressure gauge from many parts stores for a few bucks.

Do it and you'll know your real oil pressure. You replaced the sending unit but you could have a gauge problem.

Confirmation of your numbers is essential to your making good decisions. Testing will get you that data.
Click to expand...


x2...used to have a YJ...manual. did the same thing. turned out ot be a bad gauge. I spent like 10 bucks to rent the gauge...that was all i needed
 
I am having pressure issues as well and have been reading everything I can find on it. There are several threads here on it so I dont wanna start another one. So one artice I read somewhere was talking about the tube that feeds the sender has an o-ring on it that fails and has to be replaced from in the pan. Now this poster was having a mechanic fix his and replace the pump at the same time, and I dont have any ipls to look at, but if the tube thing is true a mechical gauge might show low pressure too. So if someone could point me to an ipl, or knows about the tube please post up. Thanks Don
 
chris y said:
Not hijacking but what is normal oil pressure?
Click to expand...

At least 13psi at idle, then approx 10psi per 1k RPM.
So you should have 13 psi min at idle and minimum 20 psi at 2k RPM. PSI will increase as the RPM increases.

Josh
 
MudfrogK5 said:
Working on a 90 Sport w/ 4.0.

Slowly my oil light has been coming on (no oil pressure guage). It's got to the point that it remains on when the engine is cold.
Click to expand...

Define "cold". Is the oil too cold to circulate?
 
the_weirdo said:
Define "cold". Is the oil too cold to circulate?
Click to expand...

It started when our temps were around 15-25 degrees.. When the engine would warm up it would go off.. Yesterday though it did not turn off even after the engine was warm.

I'm gonna see if auto zone has a gauge I can rent to see what the actual pressure is. I still imagine I'll be changing the pump though, I read these pumps are notorious for going out around the 150k mark. This jeep has 179k.
 
One of the best things I did to my old '91 was swap out the idiot light gauge cluster for an OEM one w/ actual gauges. Got it off Ebay for like $45 and then had to buy the new oil pressure and temp senders. I think all in all it cost me about $75 for everything. The odomether wasn't right anymore, but I didn't care, it was a POS commuter.
 
gw204 said:
One of the best things I did to my old '91 was swap out the idiot light gauge cluster for an OEM one w/ actual gauges. Got it off Ebay for like $45 and then had to buy the new oil pressure and temp senders. I think all in all it cost me about $75 for everything. The odomether wasn't right anymore, but I didn't care, it was a POS commuter.
Click to expand...

Never thought about doing that.. Do they have them with factory tach's?
 
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