yo, Get it checked w/mech gauge asap;
Installation, Sunpro Mechanical, w/T for stock gauge in an 86
Source: by Sixlitre (Malcolm H, Eddie Bauer) at
http://fullsizebronco.com/forum/showthread.php?t=31669&highlight=mech+gauge
Installation, Volt, Oil Pressure & Water Temp., Equus in an 86
Source: by Xris at
http://fullsizebronco.com/forum/showthread.php?t=27589
Also, a possibility and fyi/posterity;
Fake Oil Pressure Gauge TSB 88-05-14 for 87-88 Bronco & F Series
Source: by Ford via miesk5 at FSB
Publication Date: MARCH 2, 1988
1987-88 F-SERIES, BRONCO ISSUE: An oil pressure gauge that indicates an erratic or low reading when the engine oil pressure is within specification may be caused by the oil pressure sender. The oil pressure sender may not work properly with the magnetic oil pressure gauge.
ACTION: To correct this, install a new design oil pressure sender and new design resistor wire assembly using the following service procedure. Refer to the oil pressure sender and resistor wire application chart for the correct service parts.
OIL PRESSURE SENDER & RESISTOR WIRE APPLICATION CHART
Engine Application Description Service Part No.
5.0L, 5.8L, 7.3L and 7.5L Oil Pressure Sender E6SZ-9278-A
4.9L Oil Pressure Sender E8TZ-9278-A
All Resistor Wire Assembly E6SZ-9F291-A
1. Remove the existing oil pressure sender.
2. Install the new design oil pressure sender. Torque oil pressure sender to 10-18 lbs-ft (13-34 N-m).
3. Connect the female terminal end of the 20 ohm resister wire assembly to the oil pressure sender.
4. Connect the male terminal end of the 20 ohm resistor wire assembly to the vehicle wire harness.
PART NUMBER - PART NAME
E6SZ-9278-A - Oil Pressure Sender
E8TZ-9278-A - Oil Pressure Sender
E6SZ-9F291-A - Resistor Wire Assembly
These oil senders go bad quite often.
After doing some research it seemed like it could be the oil pressure switch, also known as a sensor or sending unit.
Remove the wire from the sender (its a switch - really), ground it w/jumper
turn the key to on.
If da gauge moves to the left, the problem is the switch
btw guage needle should be at mid-way point; if not, the wiring or guage are bad.
--
Sender Failure; "Corrosion or faulty electrical connections; If the oil pressure gauge is pegged low after the engine is running, or is pegged high after the engine is running, or if there is intermittent illumination of an oil pressure indicator light, the sender could be faulty. Related Components to Check; All appropriate electrical connections to and from the sender The oil pressure gauge or indicator light; Appropriate fuses (see Shop or Owner’s Manual for fuse layout)..." miesk5 Note; enter applicable info for year, etc.
Source: by MOTORCRAFT®
Oil Pressure Mod to Actual PSI "...short R in PCB..." info & NAPA Sender, etc.
Source: by Steve83 (Steve, That dirty old truck) at
http://www.supermotors.net/registry/media/281470