Oil Pressure Gauge

[Tristan]

Hello Gents,
I know the stock gauges aren't very good, but what would explain the following? After fully warming the truck up the oil pressure needle just drops as soon as the accelerator is released. Even just barely pushing the accelerator the needle jumps back to normal.
Video here:

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[chris142]

My 87 has a connection near the passenger fender well and the temp,oil pressure and glow plugs go through it. Mine burned up so I cut it out and used butt connectors with a good crimper.

 

[Tristan]

Any other opinions or input?


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[The Warden]

There's a very real chance the problem's electrical as opposed to being an oil pressure problem. I would advise temporarily hooking up a mechanical oil pressure gauge to the same location and see if the oil pressure actually behaves like the factory gauge is saying it is.

If it proves to be electrical, make sure the wire is in good shape, and if it is, replace the sending unit. It could also be the gauge itself in the instrument cluster, but may as well go with what's easy first, right?

 

[no mufflers]

^^^^^^ I would do this.

 

[Tristan]

Thanks Warden, that is a great idea.
Good to see you are still hanging around these parts.


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[subway]

yea the stock gauges are not much more than an indicator to me. i would also be looking real close at the connections on the engine and most likely just putting in a mechanical one so i can see actual numbers.

 

[icanfixall]

My guess is you have a charging issue. The volts are near the red danger area. the voltmeter needs to show about 13 or 14 volts when running. Bet if you figure that out the oil pressure issues will disappear.

 

[Tristan]

My guess is you have a charging issue. The volts are near the red danger area. the voltmeter needs to show about 13 or 14 volts when running. Bet if you figure that out the oil pressure issues will disappear.

So does the voltmeter show the alternators output when running?
The batteries are really old and weak, I had chalked it up to them.


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[Macrobb]

The voltmeter shows the system voltage when running. This is what the alternator is putting out(which aims to be 13-14v) minus any losses. Also, if your battery is fully dead and being charged*, it might show a tad lower for a bit until the current drops off as the battery becomes charge.


(*typically would only happen if you jump-started the truck with dead batteries, or swapped fully dead ones on while it was running)

 

[Tristan]

Makes sense. I will check things out and try the alternator off the F-250 if needed.

 

[junk]

I had a bad dash gauge that did that.