Oil pressure fluctuating

[FlakeyJake]

My rebuild 360 longblock has a whoopping 2k miles on it now. It had 60+ psi in the oil pressure department, then one day I noticed it flucutating up and down rather erratically. I didn't think much of it and replaced the sending unit. It did not help, it still fluctuated up & down but not necessarily with the RPMs.

So I started suspecting a short in the wire from the sending unit as most of the wiring on this thing is pretty crispy.

Tonite, while warming it up ( and it was really quiet in the neighborhood ) I noticed it knocking with the fluctuating oil pressure. So, it looks as if it is NOT an old wire, but truly something screwed in the oil pressure arena.

I can't believe it! This is supposedly a new pump put on with the longblock. Does anyone else have any ideas/experience with this kind of thing? Since it's saturday night, I can't call the folks I got the longblock from, but it'll be the 1st call I make on Monday. If it's just an oilpump rebuild or something....maybe it's not that bad...I hope it's not the front cover that is too worn....jeez.

What do you think? I'm starting to get quite worried about my new engine....... :confused:

[KivaKid]

Remember that those voltage regulator things for the gauges can go, but the knocking.........

[KivaKid]

Also, 60 psi sounds a little abnormally high!? I think straight up the gauge (around +/-40) should be normal, but I could be wrong.

[Lugnut]

The only way to be absolutely sure is to borrow a mechanical guage and screw it in where the sending unit is. Then you will know for sure. Don't depend on these instrument panel guages for accuracy.
The guage on my CJ-7 "danced" around for a couple of years after I rebuilt the engine. I replaced the sending unit and the guage, it still dances. I think there may be a loose connection somewhere that kinda reacts to the engine vibrating the vehicle.
Try the mechanical guage first, then you'll know for sure. Don't start worrrying yet.

[FlakeyJake]

Well, for everyone's amusement. I started thinking about my pressure problem, and came to the ( unsupported ) conclusion that it couldn't possibly NOT have oil pressure, rather, something had to be plugged or stuck or something....so I changed the oil & filter anw voila! 50+ psi steady again. ( still working on the mechanical gauges, any recommendations? )

So now...I'm wondering...did the POS Fram oil filter fail after 1500 miles? Was it plugged up? I replaced it with a purolator pure-one filter, hopefully it lasts longer than 1500 miles..

And, if it was plugged....does this mean that the engine is wearing excessively such that it plugged the filter etc.?

hmmm....

[Lugnut]

Coulda' just been a defective filter, but the engine has a by-pass passage in case the filter stops up. And, it looks like your oil pressure is steady now. No noise, no worry.

[wagdriver]

Check the grounding for the instrument panel. I don't know the location but there has to be a connection to ground some where. Also check the ground on the passenger side fender well, make sure all these connections are good solid metal to metal contact. As for the knocking others here will have better answers for that. Good Luck! ;)

[Suz]

Hmmmm...I'm experiencing the same thing as FlakeyJake. Except my oil & filter was replaced, oh, maybe 300 miles ago, so I don't know as an oil & filter change will help.

My gauge is actually up to around 80! This began AFTER we replaced the oil sending unit. Before that went, it was always right at 40.

Should I check my grounds too (and if so - stupid question, but where do I find the ground for the instrument panel?) Any other ideas as to what could be causing this and what to check out?

We're supposed to take Sasquatch on her first roadtrip 13 days from now, but suddenly all these things are popping up - yikes!

[FlakeyJake]

When this weird needle bouncing the original sending unit was registering about 60-65 psi at the high end.....my first stab at solving the problem was to buy a new sending unit...the new one only reported about 40 psi at the high end......then after changing the oil & filter....it's about 52 psi most of the time without any fluctuations....

I _still_ haven't installed the mechanical gauge to decide which of the sending units is more accurate....

Anyway, it's obvious that there are discrepancies between the different sending units.