Nov 072015
 

1996 GMC Jimmy
REPLACED OIL PRESSURE SWITCH THURSDAY NIGHT. OLD ONE WENT BAD AND LOST ALL OIL. TEST DROVE AND HAD 50 PRESSURE AND NO LEAKS. YESTERDAY MORNING SAME THING. YESTERDAY AFTERNOON IT SAID 20 PRESSURE AND DOWN TO 0 WHEN STOPPING. STILL NO LEAKS AND DIPSTICK SAYS FULL. MOVED IT FROM DRIVEWAY TO GARAGE LAST NIGHT AND PRESSURE SAID 60 AGAIN AND AGAIN THIS MORNING WHEN I STARTED IT AND NO LEAKS. WHATS WRONG?

  3 Responses to “1996 GMC JIMMY 4.3L”

  1. What you are describing sounds like a failing oil pressure sending unit, It may be possible that the new sending unit is a bad New part.

    When oil is heated it looses some of its viscosity. And when this is repeated over and over, much like it is in an engine, the oil can start to break down a bit. So when the oil is cold on the first start up of the day the oil pressure is going to be higher than it is gong to be once the engine warms up.

    The engine requires 10 psi of oil pressure per thousand rpm. So when the engine revs to 3,000 rpm it needs 30 psi, idle- 1,000 rpm needs 10 psi, etc.

  2. I CHANGED THE OIL PRESSURE SENDING UNIT AGAIN (JUST GOT HOME FROM DOING IT) AND IT’S DOING THE SAME THING. THE GAUGE ON THE DASH DROPS DOWN TO 20 AND WHEN I HAVE TO STOP IT GOES TO 0 AND THE CHECK GAUGE LIGHT COMES ON, SO IN A FEW MINUTES I AM GOING TO DO ANOTHER OIL CHANGE. AN EMPLOYEE AT AUTO ZONE SAID THAT SINCE THE SENDING UNIT BLEW THAT IT COULD HAVE MESSED WITH THE ELECTRICAL OR SOMETHING SO THEREFORE ITS NOT READING OR ABLE TO TELL THE NEW SENDING UNIT ON THERE SO I WAS WONDERING IF I SHOULD UNHOOK THE NEGATIVE BATTERY TERMINAL AND AFTER OIL CHANGE HOOK IT BACK UP, HOPING IT WILL RESET THE GAUGE? I JUST DONT UNDERSTAND IT.

  3. Sounds like it couldn’t hurt to try given it doesn’t cost anything to try. Good idea on changing the oil.

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