TC10284 113 #1 Posted August 11, 2019 (edited) I have a 518H with P218g engine. I used it about a month ago to mow the yard after I replaced the slipping plastic governor ball spacer with a metal one. Everything runs fine, but I am plagued by a flashing oil pressure light. When the issue started, I used it for maybe an hour cutting the grass and it suddenly started flashing. So I tore it down back to the gear case cover. I checked the oil pump, even removed the small threaded bolt with hex head and checked for any blockages there. Nothing. Replaced the oil pressure switch with a completely new one of the same type. Drained all previous oil (even though it only had barely an hour on it), replaced the filter with a new one too. I have checked the wiring to the LED panel and it looks good. It had a break in it half way down the wire. Originally it was just twisted and taped back together, and I didn't see the flashing light then. I have soldered it back together and still see the flashing light. This thing refuses to quit flashing at me, only briefly does it quit. This is what it does: With switch on, engine off, it flashes as it should. Crank up and it runs. Oil light quits for about a minute or two. Then will start flashing again at idle. Sometimes I can get it to quit flashing or almost quit flashing with opening the throttle some. Sometimes I cannot. I'm at a loss and I have put in a lot of time trying to get this issue resolved. Everything runs great on this engine except for this one issue. I am concerned if I keep using it, it will overheat or lock up from too little oil. Edited August 11, 2019 by TC10284 Share this post Link to post Share on other sites
lynnmor 7,823 #2 Posted August 12, 2019 Don't continue to run it, the oil pressure needs to be checked. Remove the oil pressure sensor and attach a gauge to the hole is one way to do it, but not real easy. I suspect that you have bad bearings and the oil pressure is extremely low. Share this post Link to post Share on other sites
TC10284 113 #3 Posted August 12, 2019 (edited) 1 hour ago, lynnmor said: Don't continue to run it, the oil pressure needs to be checked. Remove the oil pressure sensor and attach a gauge to the hole is one way to do it, but not real easy. I suspect that you have bad bearings and the oil pressure is extremely low. Bad bearings in which part? I still have the shroud off, so it should be a tad easier. The flywheel being in the way will be the hard part. I only have a compression tester for cylinders. I think I need something like this: https://smile.amazon.com/Mrcartool-0-500psi-Diagnostic-Automatic-Transmission/dp/B07VSDBRVX/ref=sr_1_1_sspa?crid=2N11GPXX13XP0&keywords=oil+pressure+gauge&qid=1565574384&s=gateway&sprefix=oil+pressure+%2Caps%2C147&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFUUkZRQjdUVk9JQjImZW5jcnlwdGVkSWQ9QTAwNTUxMjMyUDgyRkJaNEZWNVpZJmVuY3J5cHRlZEFkSWQ9QTAzNzM0NjY5UkQ3RjRXTlRPTzkmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl When I do a search, I'm seeing something about checking oil by-pass valve to make sure it's not open. Also, in the manual for a P218g, I see: "Normal oil pressure should be 8 psi (55 kPa) or higher at 1500 rpm when the engine is at normal operating temperature. If pressure at 1500 rpm drops below this value, inspect oil system for faulty components." (https://manuals.casecoltingersoll.com/ServiceManuals/Onan Service Manual 965-0762_watermarked.pdf) EDIT: I think you're referring to crank shaft main bearings? Is it possible that either trash/part of an old gasket in the oil from the previous run, or possibly even melted plastic got into those oil holes and is blocking oil, causing the oil light to flash? Edited August 12, 2019 by TC10284 Share this post Link to post Share on other sites
lynnmor 7,823 #4 Posted August 12, 2019 This one would be cheaper, I just don't like the high scale because you are looking for about 8psi, but it will work. Engine main bearings, and more likely, rod bearings may be the problem. It could get costly to rebuild. Anything is possible preventing oil pressure from building, the light flashing is just saying that the pressure is below minimum, if the sending unit is good. Share this post Link to post Share on other sites
TC10284 113 #5 Posted August 12, 2019 (edited) 24 minutes ago, lynnmor said: This one would be cheaper, I just don't like the high scale because you are looking for about 8psi, but it will work. Engine main bearings, and more likely, rod bearings may be the problem. It could get costly to rebuild. Anything is possible preventing oil pressure from building, the light flashing is just saying that the pressure is below minimum, if the sending unit is good. Thanks! I looked at that one first, but wasn't sure if the fittings were small enough for the oil pressure switch opening. I ordered it. Also, I looked at my spare P220g that is mostly taken apart and I am going to attempt to take out the oil pump and see if there is a build up of crud on the pick up cup and strainer wire. If nothing else, I may be able to use the oil pump from the P220g. Also going to let about 2oz of Seafoam sit in the oil. Edited August 12, 2019 by TC10284 Share this post Link to post Share on other sites
TC10284 113 #6 Posted August 14, 2019 (edited) I believe I've found the source of my low oil pressure problem (lol, and also: dang)... https://photos.app.goo.gl/H4nNZoj3zynaeo8R9 Pics of before cleaning and after. Made sure it would still pump oil by sticking pickup cup in oil and turning by hand and it still works. Cleaned the passageway anyway. What's the best way to ensure there's no more of this crud in the bottom of the pan without completely removing the engine and oil pan? As mentioned, I've changed oil and filter twice now. I figure what happened is that it sucked all this from the bottom of the pan and it stuck to the screen. Eventually got so much on there that it could not pump and started flashing the light at me. Not sure what all the previous owners did to this thing, but yeah... Edited August 14, 2019 by TC10284 Share this post Link to post Share on other sites
lynnmor 7,823 #7 Posted August 14, 2019 Wow, that engine was totally abused. Since the engine was starving for oil for a long time, you might still want to check the oil pressure. If it were mine, it would be totally disassembled and done right. If the rods and crankshaft have too much wear, you risk a total failure and end of life for that engine. For cleaning without disassembly, do several more oil changes and drain while completely hot, running the right front wheel up on something before immediate draining might help get more junk out. For those flush out runs, a cheap AC Delco PF53 filter or equivalent and lighter oil can be used, just don't work it hard. 1 Share this post Link to post Share on other sites
TC10284 113 #8 Posted August 22, 2019 (edited) Cleaning the oil pick up cup/pump and doing a more aggressive oil drain resolved the issue. Although I am closely monitoring it and not working it hard just yet. Did two laps around the very back yard (~1.5-2 acres) at increasing throttle increments and it did well in regard to no oil light flashing. Mowed a row or two as well. Issue I'm seeing now is minor surging at full throttle and close to full throttle. Just enough to be noticeable. Closing choke makes it worse. This did not happen right before I tore it down to resolve the oil pressure issue. Not sure if trash got into the carb or what. It is an aftermarket carb (cheapo from eBay). I will probably end up pulling that carb off and replacing with the original since it was soaked in cleaner for a week or two. First I will probably try draining a little oil since it's over full. Doubt that has anything to do with it, but needs to be done nonetheless. Edited August 22, 2019 by TC10284 Share this post Link to post Share on other sites
