N Board Forum - Expanded Thread Page

Subject: No oil pressure on fresh rebuild

[Back] [Return to Top of Forum]

Greg Davis    Posted 06-25-2020 at 09:10:45 [URL] [DELETE]        [Reply] [Email]  
  • No oil pressure on fresh rebuild
  • Just helped a friend with a complete overhaul on a side mount distributor 8N including the oil pump. On first startup no oil pressure. loosened some lines put more oil in filter and sort of primed the pump so to speak. Got around 20 psi on 30 weight oil when cold. Then dropped to looks like around 5. Four days later, started the tractor again, no oil pressure. Took the cap off of the filter and the oil had drained out of the filter housing with a little left in the bottom but not high enough to be at the level of the line on the side leading back to the block. Put more oil in filter loosed the line that comes out of the side of the filter housing and the gauge line where they meet at the block and kind of bled it again. We got oil pressure again after this. My question is: is there a check valve in the bottom of the oil filter canister to keep the oil from draining back into the crankcase? The reason I ask is that my friend poured oil in the filter canister and had forgotten to hook up the line on the bottom. He said oil only dripped out, not ran out quickly. I thought there may be a restriction in the bottom of the filter housing of some sort that we may need to check. We shouldn't have to prime the pump every time the tractor sits a few days.

    Tom    Posted 06-25-2020 at 09:30:32 [URL] [DELETE]        [Reply] [Email]  
  • Re: No oil pressure on fresh rebuild
  • The oil filtration on an 8N is a bypass system. A small (restricted) amount of oil passes through the filter and drains into the governor housing to lubricate the governor. The newly filtered oil does not go to the engine bearings. Filling the filter housing might have worked by flowing back the inlet line to the filter and into the engine oil gallery. I believe if priming is required some people do it through the relief valve plug in the front cover. There have been some other recent posts about the pump loosing prime.

    Greg Davis    Posted 06-25-2020 at 09:49:47 [URL] [DELETE]        [Reply] [Email]  
  • Re: No oil pressure on fresh rebuild
  • Thanks, Tom. I just thought it strange that 4 days after getting prime we had to do it again. It shouldn't have to be primed every time it is started. I've been reading on the other posts as well. Thank you for your response.

    Pete Landon    Posted 06-25-2020 at 13:24:45 [URL] [DELETE]        [Reply] [Email]  
  • Re: No oil pressure on fresh rebuild
  • I just had 1 fresh rebuild no oil pressure I did n oil t do it.Fought it for a week trying to prime it with no luck.Finnally I took it apart the 3rf time come to find out who ever did it left the front oil gally plug out ,put it in bang 60 psi.

    Greg DAvis    Posted 06-25-2020 at 13:47:15 [URL] [DELETE]        [Reply] [Email]  
  • Re: No oil pressure on fresh rebuild
  • I think the oil galley plugs are in on this one because when primed, it holds oil pressure. As long as you don't let it sit a long time, it will crank back and have pressure. If the galley plug or plugs were missing, I don't think it would ever build pressure.

    TheOldHokie    Posted 06-25-2020 at 14:57:05 [URL] [DELETE]        [Reply] [No Email]  
  • Re: No oil pressure on fresh rebuild
  • I would check the oil pump gears. Lots of defective kits on the market. Measure face width of gears to verify they are correct. Narrow gears should measure .562 and wide gears should measure .725. If more than a thousandth or two less than that the gears are defective. The defective kits are typically close to .010 undersize. They will not maintain prime or produce good pressure.

    TOH

    Greg Davis    Posted 06-25-2020 at 15:09:08 [URL] [DELETE]        [Reply] [Email]  
  • Re: No oil pressure on fresh rebuild
  • What is the best source to buy quality rebuild kit for the pump?

    TheOldHokie    Posted 06-25-2020 at 17:43:31 [URL] [DELETE]        [Reply] [No Email]  
  • Re: No oil pressure on fresh rebuild
  • I have been getting mine from Just 8N's. Derrick stopped selling the cheap kits from Atlantic and switched to A&I (or possibly Sparex) when he learned of the problem. Last I checked about $50 for those kits. Not sure what YT is selling but you could call and ask.

    TOH

    TheOldHokie    Posted 06-25-2020 at 17:45:52 [URL] [DELETE]        [Reply] [No Email]  
  • Re: No oil pressure on fresh rebuild
  • TISCO also seems to be OK.

    TOH

    [Back] [Return to Top of Forum]


    Top