inaccurate oil pressure readings

[MG2936]

From day one my gage would read 35 psi without the engine running. After start up it would read max on the 60 lb. gage. I tested with a mechanical gage and had the proper oil pressure, so I just ignored the gage problem. After 10 years the gage started to go to max reading when turning the power switch on. It was time to fix it. The sending unit was a little off so I replaced it, same problem, put a new gage on, same problem. After reading a lot of old threads on oil pressure gage problems I figured there was only one thing left that could be a problem, the wire from the gage to the sending unit. I bypassed the #36 wire in the harness, ran a new wire from the sender to the gage and presto, everything is working fine.

 

[ATPTac]

Thanks for the info, my gauge is completely inaccurate and reads maxed out sometimes and then nothing other times. Once I start digging into it, I'll definitely keep this in mind.

 

[Jeepsinker]

Yeah mine just started this. Acts like the sender though, going to replace it first and see what happens.

 

[ATPTac]

Yeah mine just started this. Acts like the sender though, going to replace it first and see what happens.

Agreed, most bad oil pressure senders I've seen go bad either peg the gauge out or show no pressure at all. Mine does both sporadically, so its making me lean towards the sender, but its still "odd" for what I'm used to seeing.

 

[Hainebd]

Just a little point but if you remove wire 36 from sender and ground gauge will go full of zero if wire 36 and gauge is good. If you ground gauge connection for wire 36 the same should happen. Now if you disconnect wire 36 from both ends and check for voltage you should have zero with everything on. Then check continuity of wire 36 and good ground, there should be none.

 

[AMGeneral]

After years and many trucks of dealing with this same problem, I scrounged enough air pressure gauges to convert all my MVs to direct reading oil pressure gauges.

A lot more trustworthy and accurate in my opinion.

Just a quick bit of info,all the 800 series trucks have this type oil pressure gauge I think.

 

[Jeepsinker]

That's good to know, as I would actually prefer to go to a manual gauge on mine as opposed to the electric.

 

[tstates]

Worked on mine today. During my recovery, it went from operational to pegged out while driving, then back to bouncy during idle. Pulled the wire lead off sender unit, and found it was way loose. Probably was kicked a time or two when a soldier was doing engine maintenance checks. Took a small screw driver and closed up the slide on fastener and she works like a charm. Mine clearly already had a new oil psi gauge in it. It was new and a different color, thats why I started where I did. Got lucky on that one. 10 minute fix.