OK.....I see a theme here....electrical problems!!!! I just put on my Edelbrock manifold and new brake booster and fired up the Fury and as soon as I turned the key I noticed the "OIL" light comes on. No noises in the engine. switched out the sender, ran a jumper from the sender to the dash light....still, whenever the key is on the light is on. Any think I am missing? Bad ground? Any other connection to the light? I am putting on a Gauge Pod with a Oil gauge on it but don't have it yet. Thanks!
Joined: Tue Oct 11 2005, 01:33AM
Location: Calgary, Alberta
Posts: 5893
As far as I remember, the oil pressure switch is "open" when the oil pressure is high enough, but closes when pressure drops too low. So, 12v is permanently connected to one side of the idiot light under the dash and the return to ground is from the other side of the lamp via a "long" wire to the pressure switch.
As such if that wire is shorted to ground anywhere between the pressure switch and the bulb, the bulb will light. The easiest way to find the short is to have someone looking at light, key on but engine not running. Now unplug the wire from the pressure switch and follow it back checking for any pinches or rubs. When you find the short, the lamp will go out.
Just to clarify, you are saying "key on", not "engine running". Although I realize you mention there are no sounds. The light should be on with the key in the Run position, but not running.
Another thing you might try is to use an ohm meter or continuity tester between the sender terminal and a good ground. If there is continuity then the issue is in the sender...or worse. While a short is more likely, this only takes a minute to test and a bad sender out of the box isn't impossible. I had 3 bad starters out of box in 1 hour once!
Well I got my gauges from Amazon....cheap 3 gauge Sunpro clusters $28. The engine is putting out close to 50psi at cold start up. whew...I know the engine has pressure at least. The light actually never goes out. The bulkhead connector is good and clean, wire has continuity all through. I'm not sure if I am even going to mess with it. I could put a tee in the back of the block and make it work for the gauge and idiot light. If I remember correctly the light would not come on before when I was cranking the car. Now it is always on. Hmmm? I don't remember ever seeing the light on ever. <span class='smallblacktext'>[ Edited Fri Feb 20 2009, 11:47PM ]</span>
Joined: Sun Jun 10 2007, 08:27PM
Location: pickering ontario canada
Posts: 100
i had a simaler problem found after i put new carc on mt oil light was coming on internitently i found wire was off and touching to ground when i hit a bump in the road
OK....since I needed to tear into the dash and start working on the speedo cable I was diagnosing this thing again. I installed the tee fitting and now have the gauge and light. I have continuity between the lead on the sending unit all the way through the fire wall bulkhead to the light socket in the dash. (grey under the hood and blue/white under the dash) But the switch also has continuity with the earth ground engine running or not. There is also continuity between the other lead (black) on the light socket and the ground. This is the 3rd switch and 2nd new one in here. Frustrating.....why does this all have continuity with the ground?
If you have continuity between the sender terminal and the threads on the sender, then the sender is bad.
Probably a silly question, it is the small light switch unit and not the large gauge sending unit right?
Also, you don't need a tee on big blocks. There are 2 oil ports on the back, there should be a plug a couple inches away from the current port. I mention this because my 71 PowerWagon had a tee for the light switch and an aftermarket gauge sender on it when I bought it. I didn't think anything of it. A couple years later I smell burning oil, smoke starts pumping out the bottom of the truck and the oil pressure starts dropping as i am jamming down the highway!!! The nipple used to attach the tee to the block cracked at the threads and sprayed oil all over the engine bay!!! Unfortunately small blocks only have one port.
correction......The switches are all good...even the original one. I tested the switch for continuity running and not with it attached to the car. When it is installed and plugged into the car it has continuity but when it is not plugged into the harness operation is good. No continuity when engine is running. Continuity when it is shut down. So the issue is not the sending unit but the wiring. It looks like the light ties into the light for the brake system light then both to the ignition switch (blue wire). OK.....One of the previous owners must have done a little creative wiring, I stripped it all back and rewired it back from the bulkhead and all is right now. Thanks for the tip on the other port for the sender, that works much better! Another DryDock victory!!!!! Thanks Again!!!! <span class='smallblacktext'>[ Edited Sun Mar 01 2009, 01:28AM ]</span>