Oil pressure sending unit testing

1950 - 1968, M38, M38A1, M170, modifications, sugestions, and ideas, official MWO's and unofficial field mods.
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Mobilized Medic
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Oil pressure sending unit testing

Post by Mobilized Medic » Mon May 27, 2013 3:25 pm

Yo Fellow MDers;
My 1954 M38A1 is running very well after I fixed some distributor internal issues.
The problem is the oil pressure has dropped precipitously without an indication of bearing or oil pump issues.
I fire it up and get 20 pounds pressure that moves a bit then falls down to 15 as warm up occurs. Oil changed out and filter new,cannister back to like new. Minimal blue smoke at start up, 25,000 miles on original engine. Runs smoothly now that distributor fixed. No clatter or squeeks.
The gauge panel wiring was cobbled by previous owner and I am about to tackle that spiders nest.
I would like to get this out for a run, last fall with good 30 to 40 pounds of pressure, ran well until electrical failure occurred.
Any ideas before I yank the oil pump (Hey, I just good the timing smack dab perfect and I do not want to screw it up again.)
Suggestions appreciated.
Mobilized (and one with my multi-tester) Medic
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Ben Dover
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Re: Oil pressure sending unit testing

Post by Ben Dover » Mon May 27, 2013 3:57 pm

Do you have a 120# or 60# Gauge? Is the sending unit rated the same?. It will have 60# or 120# stamped on the side of the connector. Brands make no difference. The 120# gauges are not very accurate and were not back when the M-38A1 was new. The Army would update with 60# set up during visits to support units or with engine change.
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