I have a wierd problem with my oil pressure guage. When I picked the truck up from the DRMO, after a half mile or so I had the hindsight to check the oil pressure guage. It was reading ZERO! Well, I was at this point passing the flight line of the ANG base with no place to pull over, the engine was sounding fine and it had only 16,000 miles since TEAD rebuild, so I just kept on trucking. Another 1/2 mile and the pressure jumped up to 60 PSI (I have a 120 PSI guage), so I started feeling a little more comfortable.
The rest of the 230 miles home the guage read 120 PSI the whole time, even after I shut the engine off in my driveway. The very next day I bought and installed a mechanical oil pressure guage. After starting the engine, the mechanical guage read 50 PSI at idle and 75 PSI at 2000 RPM.
I found the very detailed section on diagnosing oil pressure guage problems in TM 9-2320-316-20. First, you remove lead 36 from the oil pressure sender, turn the accessory/ignition switch on, and the oil pressure guage should read MINIMUM. Then you ground lead 36 and the guage should read MAXIMUM. Following that are several tests to check out the oil pressure sender and further check out the wiring.
When I disconnected lead 36 from the oil pressure sender and turned the accessory/ignition switch on, the guage jumped up to 120 and stayed there. When I turned the accessory/ignition switch off, the guage stayed at 120 PSI for several seconds after then slowly dropped down to zero! All of the other guages droped to zero as soon as I turned the accessory/ignition switch off.
At this point I decided to pull out my instrument panel and check out the connections to the guage. Unfortunately, I have a personnel heater and most of the IP wiring was routed behind the heater duct, so I couldn't pull the IP out far enough to be able to do anything. By then I had run out of time, so I put the IP back in place and quit for the day.
Next chance I get I'll remove the heater duct, pull out the IP and check out the wiring. In the meantime, does anyone have any thoughts why my oil pressure guage is misbehaving so badly? I doubt that having the electrical connections reversed at the guage would cause a problem like this. I suspect I have a bad guage. I hope it is the guage, as a new guage is a WHOLE lot cheaper that a 120 PSI sending unit!
The rest of the 230 miles home the guage read 120 PSI the whole time, even after I shut the engine off in my driveway. The very next day I bought and installed a mechanical oil pressure guage. After starting the engine, the mechanical guage read 50 PSI at idle and 75 PSI at 2000 RPM.
I found the very detailed section on diagnosing oil pressure guage problems in TM 9-2320-316-20. First, you remove lead 36 from the oil pressure sender, turn the accessory/ignition switch on, and the oil pressure guage should read MINIMUM. Then you ground lead 36 and the guage should read MAXIMUM. Following that are several tests to check out the oil pressure sender and further check out the wiring.
When I disconnected lead 36 from the oil pressure sender and turned the accessory/ignition switch on, the guage jumped up to 120 and stayed there. When I turned the accessory/ignition switch off, the guage stayed at 120 PSI for several seconds after then slowly dropped down to zero! All of the other guages droped to zero as soon as I turned the accessory/ignition switch off.
At this point I decided to pull out my instrument panel and check out the connections to the guage. Unfortunately, I have a personnel heater and most of the IP wiring was routed behind the heater duct, so I couldn't pull the IP out far enough to be able to do anything. By then I had run out of time, so I put the IP back in place and quit for the day.
Next chance I get I'll remove the heater duct, pull out the IP and check out the wiring. In the meantime, does anyone have any thoughts why my oil pressure guage is misbehaving so badly? I doubt that having the electrical connections reversed at the guage would cause a problem like this. I suspect I have a bad guage. I hope it is the guage, as a new guage is a WHOLE lot cheaper that a 120 PSI sending unit!
