RandomHero180

Hi, long time lurker here first time poster. I have a 99 Grand Cherokee with a 4.0L I6

I have been searching the forums and haven't found this issue I am having so here it is.

I recently replaced my oil pressure sending unit because when I came to an idle it would drop to zero and the 'Check Gauges' light would come on. Two different garages, one being a Jeep dealer, said this was this issue.

Now that it has been replaced it is working better, but I don't feel like it is working the way it is supposed to. At idle the pressure drops to between 0 and 10psi. Not low enough for the light to come on, but lower then normal I think.

The other issue is it acts like a tachometer, psi increase when I accelerate and stay just above 40psi when at highway speeds and then drop all the way down to 8ish psi when stopped

I never noticed this before I had the original sending unit issue.

So my question is:

1. Did a get a bad sending unit?
2. Could it be a short in the wiring?
3. Is it possibly a oil pump or some other issue as well?

Thanks for any help, this has been bugging me the past week.

zr2toxj

I would put a mechanical gauge on it, right at the block and check pressure there. Yes it could be the oil pump, or other issues internally. If the mech gauge shows proper pressure, then start looking at bad grounds, etc. If it shows the same as the gauge in the dash, then it's a bad pump, etc.