I have a 97 f150 with a 4.6 2wd and have recently replaced the timing chain cover. Due to my work schedule I could only work on it for a couple hours every few weeks so it spent some time with the oil pan slightly open (not completely off but still not sealed.

I just got everything back together and filled it with oil and marvel oil and ran it for a few before doing another complete oil change with new filter, oil pressure sensor and all.

It is still doing it, it starts and runs fine but in less than 10 minutes the oil pressure gauge maxes out!! I'm talking about full on past the red.

I have the sender that has the one stud coming off of it so is there anyway to check the pressure at the sensor to make sure the gauge is reading correct?

 

It's not a linear gauge - it's an idiot gauge. Sounds to me like your new sender is defective.

You can remove the sender, get a T-fitting, and screw in a mechanical gauge.

 

what should the psi be reading?

 

A stab in the dark would be around 30psi at idle, but glc probably can give a more accurate answer

 

GLC?

I hooked up a mechanical gauge and on startup it reads 75 psi, then after idling for a few minutes it works its way down to 40 psi?

Does that sound good?

 

What weight oil are you using?

 

5w30

 

Those numbers are fine. Your sender unit, OTOH...

 

I've replaced my sending unit 3 times now and it still doesn't work. How do I go about fixing my gauge?

 

Send the cluster in to a repair center.

 

I don't know about these trucks but the 1970s and 80s vehicles used a small voltage regulator on the instrument panel circuit board to regulate the instrument voltages. Without it, the gauges would fluctuate with the battery voltage.

It might be worth looking into.

You should also be able to attach a volt meter to the output of your oil pressure sensor and and see if it changes and the change more or less matches what your oil pressure gauge is showing.

Again I don't know on these trucks but on the older model vehicles 40 PSI was about right. 75 PSI was too high and on the older model engines would indicate a stuck oil pressure relief valve. Again on older MOPAR engines; you could short the pressure sensor to ground and the gauge should read right at the top mark.

 

Well now, the oil pressure is reading fine and my temp gauge is maxed....ON A COLD START WITH THE KEY OFF!?!?!?!

 

Problems with two different gauges/systems? I would start looking for shorted or damaged wiring between the engine and the instrument panel.

 

That is not how this cluster operates. The oil pressure "gauge" is nothing more than a simple mechanical idiot light. Any pressure over 4 psi is supposed to cause it to read mid-scale.
Again, not how this system works. He doesn't have a sensor unit, he has a simple pressure switch.
Send the cluster in to a repair center.

 

projectSHO89,
could he roll the dice with a salvage yard replacement?
I, personally, understand there's a risk that you could get one that's just as kaput. But, at the same time he could luck out or at the very least have a speedometer while the original is being fixed.
If he was to go that way, what, other than having the same face do you have to know?