AuroraGirl
I'm Awesome
Does the '90 model year 5.7L still use the same fist-sized, green-stripe oil pressure sending unit down by the oil filter as the '88--'89?
They've got a known-high failure rate. They can read too low, they can read too high, and they can just read whatever they damn well please at any given moment.
If so, many parts-store computers list the WRONG sending unit for that application. What they list is too big, doesn't fit, and the heat shield has to be forced over the thing.
Left: Correct "green stripe" sending unit with heat shield. Right: Incorrect, too-big unit specified by NAPA and others.
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Correct P/Ns are
BWD S4320 It has a silver case, and green paint around the end with the electrical connector.
http://weblink.carquest.com/acl/?mfg...rtNumber=S4320
The NAPA / Echlin crossover from that number is OP6729. AutoZone sells it as PS150.
Best I can tell, they're all sourced from the same manufacturer.
If this is what you have, consider moving the wire up to the distributor area. Buy a 3-wire sensor, and the 3-wire pigtail. Take the two existing wires by the distributor, add the third one from the original sending unit, and use the more-reliable 3-wire switch/sending unit from a newer 5.7L.
BULLETIN NUMBER: 93-8C-28 SECTION: 8C NUMBER: 2 CORPORATE REFERENCE NUMBER: 268304 DATE: November 1992 SUBJECT: INCORRECT OR ERRATIC OIL PRESSURE READINGS (INSTALL NEW [1][2]OIL PRESSURE SENSOR) MODELS: 1990-93 ALL LIGHT DUTY MODELS Owners of some 1990-93 light duty trucks may comment that the oil pressure dash gauge reads high, has erratic movement or is inoperative. The internal resistance wire in the [1][2]oil pressure sensor may not be properly supported, resulting in an intermittent open condition. SERVICE PROCEDURE Check for normal causes of high oil pressure gage readings (high resistance or open circuit), such as a poor ground path caused by loose sensor mounting, oil cooler adapter loose, or poor electrical connections. If no cause can be found, replace the [1][2]oil pressure sensor following the procedure. 1. Disconnect the negative battery cable. 2. Remove the wiring harness connector from the [1][2]oil pressure sensor. 3. Remove the [1][2]oil pressure sensor. 4. Install the new [1][2]oil pressure sensor. 5. Connect the wiring harness connector to the [1][2]oil pressure sensor. 6. Connect the negative battery cable. PARTS INFORMATION
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New [1][2]Oil Pressure Sensor Part Numbers for the 1990-93 models Parts are currently available from GMSPO |