4.0 Oil pressure needle erratic.

[chessman21]

I replaced the sencor about a year ago. I added a quart of Havoline 5/30 to my 10/30 Castrol gtx to bring level up to the mark and today the Gage needle is jumping hard back and forth when i sit still and idle and it does so hard i can hear the needle bouncing off the "0" peg. Normally needle doesn't move at all.. May that be the wire connection cap loosing contact or something more serious?

I drive it 20 miles coming home but it didnt do again so far.

 

[adsm08]

It could be a loose connection.

 

[chessman21]

91 4.0 dumb questions.

Well, i know i could be but whats the more likely, the pump or connection cap on censor? Iv got to jack up truck cause i dont fit and im on oxygen 24/7 and whats considerd to be simple for most proves to be very difficult for me. This is the reasoning behind most of my super simplistic non answered questions on this forum about this truck.

Is the pump a simple bolt on? under pan?

 

[adsm08]

Oil pressure is purely a mechanical function. It is very unlikely that it is intermittent. Thus a bouncing needle is not likely to be related to a genuine pressure problem, but not impossible.

I think the first thing I would do, since it is the least invasive, is probably to get an aligator clip test wire, use it to hook the sensor's wire to the block, and go for a drive. If the issue persists, wiring, or gauge.

If it doesn't then you have a choice to make, since you are not fully able-bodied it seems. You either need to install a mechanical gauge and see what it says the pressure is doing, or replace the sensor and hope that was the problem.

The oil pump is not a simple affair. The engine has to come at least partway out to get to it, but for as far as you have to take it out to get the pan off do to the pump you may as well pull it the whole way out and put it on a stand to do the job.

 

[chessman21]

I drove it today and again after truck Got to operating temperature in stop & go traffic and only at a stopped idle tho and its definitely a mini series of hard complete bounce from one side to the other once it starts. If i raise rpms up at all it returns to were it allways reads after i installed it.. As i said i do have a mixture of brand of 5w &10w30 oil in crank case
(rear main leak) And it started right after adding a quart. ANd filter is past due for another doesnt seem like none of that would cause that bouncing like that. Is it possable for the filter to be so dirty oil wont go through it unless rpms are up some?

 

[adsm08]

Mixing oil brand or viscosity won't cause this.

Oil filters have bypass valves in them to prevent oil starvation if the filter plugs up completely, so that is also unlikely.

This could also be an alternator issue. Do that first test to narrow this down to an electric or oil pressure issue.

 

[cp2295]

Well, good oil filters have bypass valves stock with a motorcraft FL1A haha, I agree though, I doubt it’s in internal engine issue especially if you don’t hear any accompanying noises with it. You’d likely hear the lifters collapsing if it got seriously low.

The thing with these dummy ford gauges is that they are reading in the center above 3psi and read zero pressure below that.

Best to put a mechanical gauge in and know for sure what your pressure is, if you are unable to do it it should not be too expensive for someone to


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