850 T3 Oil Light Warning Light - PCV?

[tonyduc]

After about a 1/2 hour ride, my engine oil light went on. This was my first ride of the season, bike hasn't started in six months, it ran well otherwise. When I got home I let it sit a few minutes, then upon starting it again after 10 secs the light went on again. Could this be due to a stuck PCV valve ? Is the PCV on top of the case where that tank reservoir feeds a line into? Does the PCV just pull out ?
Thanks
Tony

[Loop Tonti EV]

It's probably a faulty oil pressure switch. If you actually rode it with the warning light on for more than a couple minutes and the engine isn't toasted then it likely still has oil pressure. If the crankcase vent valve would have stuck it probably would have been bleeding motor oil out of the seals and vent.
I would recommend draining the oil, drop the sump and make sure the oil filter didn't come loose. Change the filter and put fresh oil in it if it's been sitting for a while. You will likely end up replacing the pressure switch.
I used an old switch to make an adapter to connect an oil pressure gauge for testing purposes. It's easy to do if you are slightly handy with tools.
Where are you located? Perhaps a member here would be close by and could assist you in some way.
Did you recently wash it. I've seen instances where the light will come on due to moisture fouling the switch.

[Chuck in Indiana]

I'm guessing there is trouble in river city. Normally a bad switch just sticks. Hopefully, that is all it is.. but.. if you ran it for any length of time with low oil pressure..
That switch comes on when pressure is under 5 psi. There's no oil filter on a T3..

[jacksonracingcomau]

Oil filter inside sump but no need to look now
As said if no pressure , engine Is Donald in seconds
Electric switch on top of crankcase is generic, local car bits shop will have one
If more than that, get your overalls on

[Two Checks]

All T3s had filters.
Early Ts did not. Latest 75 Ts did.

[jwinwi]

Remove oil pan, check that filter and oil pressure relief valve are both tight just to be sure.

[Gliderjohn]

I am amazed that you could even see that the light was on i daylight. I can only see any of my dash lights in dim or dark light.
GliderJohn

[tonyduc]

I do put a hose clamp on the filter - anchored in a way to keep it from unscrewing, try to do this on all my bikes. I changed the oil last Fall, so hate to drop the sump first thing. Easiest thing to start with is the indicator sensor. If the PCV valve is stuck would the build up in back pressure and then lower the oil psi?
Thanks for all the help
Tony

[berniebee]

Just to answer directly to the question, the low oil pressure light being on has nothing to do with the PCV valve. One more possibility: the wiring from oil pressure switch is intermittently shorting to the frame.

[acogoff]

     My original oil pressure sending unit only lasted 40 years. Cheep Junk, anyway. Why would a person buy a vehicle that started having problems after only 40 years?

[Old Jock]

All the guys have already told you what to do

You could start with the pressure switch and also confirm the circuit, any earth on a loose wire would light it up.

I'd drain the oil and drop the sump too, either get it into a clean container and reuse it or put in new oil. The price of oil is cheap compared to trashed bottom end bearings or worse. Checks as already suggested.

Only thing to add and it's a long shot do you know oil temp? I'm thinking if it took a few minutes to come back on could it just be toasty and the oil is getting too thin?

Personally though I'd be terrified, I'd check the switch or just install a new one. I'd also drop the sump and do the checks, before I started the bike again.

Lastly I'd try to ascertain if it's overheating, in my experience with the older bikes you'll lose power big time before the oil pressure gets that low, unless its at idle when a really hot engine might cause the light to come on, however its normally more of a flicker

Good Luck with it and please let us all know the outcome

[Tom H]

A quick test to see if oil is pumping, but you won't know the pressure. Pull the spark plugs, loosen on of the banjo feed lines to the head and crank the engine over.

A little longer test. There is a M12 to 1/8" pipe adapter. Screw the adapter in where the pressure switch goes and hook up a mechanical oil pressure gauge. Again crank it over with no spark plugs.

You can also add a permanent electrical gauge and use the oil switch as well with some brass pipe and a pipe T.

Tom

[Antietam Classic Cycle]

For $30 one can buy a cheap tester and not wonder if there's oil pressure or not:
https://www.harborfreight.com/engine-oil-pressure-test-kit-62621.html
https://www.amazon.com/piece-Engine-Pressure-Tester-Diagnostic/dp/B076S1BMSJ

[Chuck in Indiana]

All T3s had filters.
Early Ts did not. Latest 75 Ts did.

Sorry.. my bad.  No excuses except not enough coffee yet this morning.  In that case, it *could* be a loose oil filter. Still not good. UFIs have been known to have gasket issues.

[Perazzimx14]

Make sure everything is properly grounded.

[Chuck in Indiana]

^^^^ Agreed.
Yeah, but..

let it sit a few minutes, then upon starting it again after 10 secs the light went on again.

Makes me think it is more than a sticking switch/bad ground, etc. <shrug> Certainly, I would proceed with caution.

[John A]

i didn't read all the posts but if you take the lead from the switch and ground it, the light will come on.

[Kiwi_Roy]

If ever you are out riding and the oil light comes on turn off the engine straight away then disconnect the oil supply to one head,
Start the bike and see if the oil just dribbles out or shoots out with gusto, the latter is confirmation of good pressure and its probably just a bad switch.

Oops Tom said that allready

A quick test to see if oil is pumping, but you won't know the pressure. Pull the spark plugs, loosen on of the banjo feed lines to the head and crank the engine over.

A little longer test. There is a M12 to 1/8" pipe adapter. Screw the adapter in where the pressure switch goes and hook up a mechanical oil pressure gauge. Again crank it over with no spark plugs.

You can also add a permanent electrical gauge and use the oil switch as well with some brass pipe and a pipe T.

Tom

[tonyduc]

I dropped the sump and everything looks good, filter and screen are fine. Wiring from the switch checks out, so I ordered a new switch. BTW, when the engine was rebuilt the oil switch is one of the things I did not replace, so it may be 45 years old. Not too bad considering most modern cars I have had need some kinda sensor replaced at 3-5 years old ! If it was the switch I'll update the post.
Thanks

[tonyduc]

It was the oil switch, just installed a new one and everything is fine.
Thanks for all the help.
Tony

[Tom H]

Congrats!

Tom

[Kiwi_Roy]

I am amazed that you could even see that the light was on i daylight. I can only see any of my dash lights in dim or dark light.
GliderJohn

The reason I replace all my idiot lights fore LEDs.
I don't use sockets but solder the wires straight to the lamps for reliability.
I buy these lamps https://www.superbrightleds.com/moreinfo/miniature-and-subminiature-bulbs/194-led-bulb-1-led-miniature-wedge-retrofit-car/197/ 100 at a time and use them in all sorts of projects, they are not polarity sensitive. When using LEDs just make sure the colour matches the bezel colour.