Oil Pressure Gauge Problem
Thread Starter
Instructor
Joined: Oct 2007
Posts: 100
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From: Andover MN
Oil Pressure Gauge Problem
My problem is on my 1978, L82 with a 4speed. My OEM oil pressure gauge only reads 20psi and will move up only slightly when the engine RPM is increased. I replaced the oil pressure switch, no change. Replaced the gauge with an OEM gauge, no change. Cleaned the printed circuit connections and checked continuity, no change. Checked the wire from the switch to the gauge and continuity is fine also replaced the connector at the switch end. When the wire at the switch is disconnected and the ignition is on the gauge reads well past 80psi. When the switch wire is reconnected and the ignition is turned to on the gauge goes back to 0psi. I removed the oil filter, pressure switch and piping and cleaned out all of the passageways which were clean). Reinstalled everything, without any teflon tape, no change. Hooked up a mechanical oil pressure gauge and it showed around 30psi at idle and went up to around 65psi at higher rpms. The only other odd thing that happened before the gauge quit working is one day while driving I noticed the gauge was bouncing between 0 and as far as it could go to the right. It would then settle down for awhile and start again. I am out of ideas, have a Wix filter on it, 10/40 oil.
Any ideas or help would be appreciated!!!!!!
Dan
Any ideas or help would be appreciated!!!!!!
Dan
Former Vendor
Joined: Aug 2006
Posts: 76,656
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Ok.. quick test to see if the gauge/wiring is fine..
turn the key on.. and remove the wire from the sending unit. The gauge should peg. Then take the same wire and ground it out to the engine block and the gauge should go to zero.
The oil pressure gauge is a twin of the fuel gauge only the movement is not as dampened. The scale is the same too..
So.. here is how to test the sending unit without taking it out.
0 - 90 ohms is the scale...
so
22.5 ohms is your first mark on the gauge or aprox. 20lbs.
45 ohms is 40lbs.
67.5 ohms is your second mark or 60lbs.
90 ohms is 80lbs.
Now my biggest question is the 20 lbs of pressure. You sound worried about that and 20 lbs is plenty. If you have just installed a new engine there are other factors that will play a part in this.. for example, how much clearance do you have on the rear main...
IMHO,
Willcox
turn the key on.. and remove the wire from the sending unit. The gauge should peg. Then take the same wire and ground it out to the engine block and the gauge should go to zero.
The oil pressure gauge is a twin of the fuel gauge only the movement is not as dampened. The scale is the same too..
So.. here is how to test the sending unit without taking it out.
0 - 90 ohms is the scale...
so
22.5 ohms is your first mark on the gauge or aprox. 20lbs.
45 ohms is 40lbs.
67.5 ohms is your second mark or 60lbs.
90 ohms is 80lbs.
Now my biggest question is the 20 lbs of pressure. You sound worried about that and 20 lbs is plenty. If you have just installed a new engine there are other factors that will play a part in this.. for example, how much clearance do you have on the rear main...
IMHO,
Willcox
