onan 20hp oil light

[welderdude 1]

Hello everyone this is my first post to this site.but I recently bought a 520-h, and ran it for about 20 min when I got home everthing was good.so I started a maintenance on it oil, filter etc. and started it without the air filer for a few moments shut down installed air filter cranked back up and oil light started flashing any one might know whats going on? Since then I've washed the motor of dirt and grime got it torn down to access oil sending unit that's as far as I 've gotten and did notice a hose running off the air filter just kind of handing on back side of motor im sure it's got a home also I've looked but dont see where it attached under dash ares

[Martin 2,131]

welcome to the forum...

 

on all the Onan twins the oil light usually flashes with no oil pressure. not sure at what psi low oil pressure it would flash. its probably in the manual, i will check on that. was the engine running when it was flashing?

 

i think the hose running from the air cleaner is for a warning light for dirty air cleaner element. the 520 had a vacuum gauge but i think that would be read from below the carb throttle blade.

[welderdude 1]

Yes it was running and when you just turn switch on it will blink.I've gotten a new oil sending unit and a mechanical oil gauge that im going to hook up when.I get to the shop.and where does the tube hook up,im assuming to the vac gauge on the dash but didnt see any where it would go, maybe didnt look good enough.

[varosd 1,185]

the air filter sensor hose should connect to the "firewall" to the right of the battery. small nipple on the sensor always breaks off and it may still be in the end of the hose.

 

bad picture  sorry!

 

[Martin 2,131]

looks like Don came through with a pic.

 

just to be clear, when you turn the ignition on it should blink, then it should go out when the engine starts and is running.......

 

if it continues to blink either you have no oil pressure or bad sender etc....

[welderdude 1]

Yes when its running the light continuous flashes at idle and mid throttle.think I'll do a mechanical gauge along with a new oil sending sensor.think I read somewhere a ps15(part number) oil gauge from the parts house would work on an onan they have a 3-9 psi range.I could be wrong.

[gwest_ca-(File Mod) 11,029]

Do you have the tractor's model number? If I remember correctly the oil pressure switch also controls the hourmeter. Looking at the correct wiring diagram should confirm this.

 

Garry

[boomers_influence 106]

welderdude

the onan P 16 18  and 20 hp will usually open the relief valve at about 20 PSI.

thank you. boomer.  ( the used onan engine parts guy )

[welderdude 1]

The model number is 41200e02. Sorry, today the first chance I had to look at it.hadnt had time to do anything else as far as the oil pressure goes.thanks in advance.

[gwest_ca-(File Mod) 11,029]

Here is the wiring diagram

 

Garry

[Martin 2,131]

you may have a sender/ light problem (i.e. not calibrated properly) but boomer touched on another area you should at least look at if the sender doesn't fix the problem.

 

the relief valve limits oil pressure to about 20 psi by a spring and valve. if the spring is weak, missing or the valve is stuck slightly open you might not have enough oil pressure when the oil pump is turning slower at idle and lower mid rpm.

you say the oil pressure light goes out at higher rpm, maybe then the pump is turning high enough to get the pressure up to where the sender isn't reading low and flashing the light.

this also brings up a scenario where the pump maybe worn enough, or bearing clearances in the engine are excessive, and the pump just isn't able to supply enough oil pressure to make the light go out at the lower rpms.

 

only way to know for sure what the pressure is at all rpm is to hook up a known good (accurate) mechanical oil pressure gauge and run the engine. the mechanical gauges are cheap enough, i have one i picked up for $10 from the local farm store, just a small length of oil pressure hose, hook it up in place of the sender, (or t it if you want to see at what point the sender is working) zip tie the gauge to the tractor and run it.

 

Edited August 2, 2014 by Martin

[welderdude 1]

Here is the wiring diagram

Garry

Hey gwest, couldn't get the diagram to load, but ill keep trying.thanks

[546cowboy 301]

You did put 30w oil in it right? Did you put an Onan filter in it or an aftermarket? Just saying if the oil pressure was OK before you changed oil, and now you have a blinking light, I would think something you did caused the problem. I would suspect the replacement oil filter first before I started taking things apart. Over diagnosing a problem is a common mistake you know?  

[welderdude 1]

The oil and filter was in the mower when I got it and ran good with no lights blinking, the only thing is when I started the mower the air cleaner/fliter was not in place (cause i had it off to blast the muffler and paint)when it was running for 5 min thats when the light started blinking.so I changed the oil and filter and new air cleaner element thinking oil change might "magically" fix the light from blinking but NOT.so im in the process of new sending unit and a mechanical oil gauge combination just hadn't had time to get back to it.if I dont hurry i wont have to worry about mowing grass this year.still using my old 93 model craftsman mower that I have to work on every time I mow with it.got to love that.

Edited August 12, 2014 by welderdude

[546cowboy 301]

There is another thing about the oil senders on these Onans, there were more than one which I found out once. I had an engine that was using quite a bit of oil and I had another P-220 and decided to change them. Swapped the engines and the first time I fired it up the oil light was blinking. So I pulled the cover off and low and behold there was a different sending unit than the other engine had. I ended up having to change the engine wire harness to get the light to turn off along with the sending unit. Just saying there is a difference between years.

[tiggercl 28]

 Just saying there is a difference between years.

Sure is... ;o)

Edited August 13, 2014 by tiggercl

[welderdude 1]

Hello everyone, finally had a chance to finish up my oil sending unit and mechanical gague, was looking at the air filter switch beside battery, so you have the input hose side and on the back of the plastic unit looks to be another hose hook up port on the back side, im assuming there a hose the hook to that as well? Didnt see any hose hanging loose , is there a hose that goes there, the vaccum gauge looks to be complete(no access) someone before me has done electric wiring to the mower, I seen where the fuse block has gotten hot and melted small part of plastic housing and new wires have been attached with inline fuse blade type.have not started the mower to try out the oil pressure switch/mechanical gauge.planning on that tomorrow or as soon as I can.thanks

[welderdude 1]

Well my 520-h is back in business, got my blinking oil light off with new sender unit and mechanical gauge is working ended up using epoxy to attach my air filter port back on the sensor block,so a very very thank you for all on the redsquare forum help, the info on here is very much appreciated!