Lost oil pressure

[jkoerpel]

Hey all -

Yesterday everything was fine...today the oil light won't go out.  

Definitely oil in there.  I've ordered another filter/metal shim/o-ring and should be here tomorrow.  

Apart from the entire oil pump failing or a faulty pressure switch, is there anything else you can think of that would cause this to happen?  

My guess is the $2000 o-ring failed?  Hopefully better days tomorrow.  

Josh

[Bob_Roller]

There's a filter bypass  valve inside the filter housing, you can check to see if it still seated .

Check the wire that goes to the oil pressure switch, I found mine had missing insulation on the wire .

It had gotten old and hardened cracked and fell off .

The low oil pressure circuit is just looking for a ground, a bare wire touching the engine will be enough to turn the light on .

Just a thought, because it has happened before, you don't have the oil light and the GEN charge indication light mixed up do you ??

[donbmw]

What work have you done. Oil change. Replace oring at oil pump.

[jkoerpel]

So far all i've done is change the oil, not the filter.  The filter/o-ring/shim should be here today, so I'll change those out either tonight or tomorrow.

Bob, that filter bypass valve is inside the canister?  

And I've never tried, but can one remove the oil filter without draining the sump?  

[Julio A.]

If you remove the oil filter without draining the sump, think of removing a  dam instantly from a river during rainy season.

The Filter bypass valve is in the cylinder, it is a circular hole around 5mm in diameter .

[montmil]

You can change the oil filter and save the fresh oil in the crankcase...

Gather some padding material and lean the bike over as far as you safely can do so. Perhaps engage first gear to prevent rolling.

Or, simply wipe clean the oil drain plug area, drain the fresh juice into a clean pan and refill the engine after the filter change.

I also believe you may have a short to ground that is causing the oil warning lamp to ignite. Chase the wire.

[Bob_Roller]

The oil filter is above the oil level in the oil sump, you should get the same amount of oil out of the filter cavity, regardless if oil is in the sump or not .

[Barry]

I've never tried, but can one remove the oil filter without draining the sump?  

Yes and Bob's right. Leaning over just saves some of the oil in the filter tube. I've done it before a couple of times. Lean the bike over as Monte suggested. You'll lose only a few cc's.

Having said that I'd be surprised if it's the filter installation. The oil pressure switch is set so low that it even with a leaky 2000$ O ring the light would probably stay off except perhaps at idle.

[jkoerpel]

It was a short to ground!!

I took a look at the oil pressure switch, cleaned it off and started tracing back as far as I could.  After cleaning, I tried the bike again and the light went off!  Success!

Turned the bike back off, put the tank back on, started up and...light on!  Switched the petcock on, turned the bike over and light off!  Jiggled the tank, light on!  I guess you get the picture.  

Somewhere under the tank or between the back of the tank and the instrument cluster theres a short to ground lighting the light.  It started to rain so couldn't chase it down tonight, but soon...

Thanks for all the input!  I got the o-ring and filter and such today from max bmw...so now just gotta wait for a sunny day to change everything out.  I appreciate all the help!!!!

[Bob_Roller]

Great, at least you don't have an oil pressure problem with the engine !!!!! 8-) 8-) 8-) 8-) 8-) 8-) 8-)

[tvrla]

Excellent news! Shouldn't be too hard finding the source now.

[montmil]

The first most excellent rule for troubleshooting old Airheads is to check all the simple stuff first.

The second rule to remember is that it's usually the simple stuff.

You may want to write that down and nail the note on your shop wall. That's where mine is.

[jkoerpel]

Excellent news! Shouldn't be too hard finding the source now.  

Or so I thought...

The quick version is, I guess I don't know how to chase down electrical shorts properly.  Cause this is proving to be a bit trickier than first thought.  

So just to be clear upfront...oil pressure in the crankcase and subsequent triggering of the oil pressure switch interrupts the ground and shuts off the light?  If that's correct and my light is grounding out somewhere before the switch, I should theoretically be able to disconnect my oil pressure switch and the light should stay illuminated.  No dice.  Plan B: search for wire chafe.  None that I could see.  Plan C: jiggle wires along the wiring harness and look for light flickering.  

This sort of happened, and it seemed like it was happening more frequently around the harness/sleeve that directs into the instrument cluster.  So I cut it open and checked wires - turns out there was a lot of water trapped inside the sleeve 'U' bend...looked old too.  So I thought to myself, 'this has to be contributing to the problem'.  I drained and dried everything out and yet, alas, the light still burns bright...taunting me with it's electromotive presence.  

What I don't understand: Tank wiggling is the only thing that sometimes extinguishes the light.  And not immediately.  I have to shut the bike off, then wiggle, then restart and sometimes it works.

I have a volt meter.  Can anyone shed some light on the best way to check for this short?  

Oh and monte...I don't have a shop wall (just a gravel driveway of sorts) to nail to.  How about tattoos...

[nhmaf]

To start off, put the multimeter in DC Volts mode, clip the black lead onto a solid, clean unpainted bolt on the engine case or the (-) terminal on the battery, slide the plug that connects to the top of the oil pressure switch upward a bit so you can make good contact there with the red lead.  with the key switch on, check for voltage (should be 0 or something ve small) .  Then start up bike and observe the light.  MAybe have someone help you with either reading the meter, holding the lead on or wiggling the tank.

It is a bit of a pain, but not technically hard to get a short bit of copper tube that will fit inside your fuel line, and some extra fuel line - you can then remove the tank and have it setting on a bench or someplace suitably elevated but off the bike and run the extra fuel line and splice it into the 1 main line on your bike.  You're then free to wiggle things around that would be under the fuel tank and have the engine run to observe oil light behavior.

[Bob_Roller]

Are there any chafe marks on the bottom of the fuel tank up against the frame tube, where the wires run itself, like through the paint and primer, down to bare metal ?

You may have a ground when the fuel tank is installed, but when the tank is removed, the ground is removed and you can't duplicate the problem .

Or possibly when the fuel tank is installed, it pushes down on the wire harness and you have a bare wire, it makes contact with something under the tank area .