Lister Diesel ST1 oil flow.

Discussion in 'Help Wanted' started by lathejack, Oct 11, 2016.

  1. lathejack

    lathejack New Member

    I have this Lister ST1, complete with electric start and alternator, that I am about to get running after many years of inactivity.

    I'm giving it a full service but before I go cranking the engine over I wanted to force fresh oil under pressure into the main oil way leading to the crank bearings, rather than wait for the pump to do its job.

    With a spotlessly clean high pressure oil can I pumped oil down the centre oil way that the filter screws onto, but the oil instantly just flows freely back out the small oil way to the left, that is the feed from the pump to the filter. I expected that once I had filled the oil way there would be resistance from the plain bearings and I could then generate some pressure while pumping the oil can to force fresh lube through the bearings.

    So why is the oil doing a short circuit? Are there ball valves or something built into the casing that maybe faulty? I have not come across this before. I know I could have just primed and fitted the new filter and then probably pumped oil through the hole above the filter after removing the small plug. But now I have discovered what may or may not be a fault, I cannot see why the oil feed to the filter would be connected to the main oil way after the filter. This would seem to allow the oil to bypass the filter, the oil filter already has a bypass valve buit into it, incase the filter becomes blocked.

    Honestly! You try and do a bit of good by making an extra effort and are rewarded with extra worry.
     
  2. highrange

    highrange Member

    Knowing nothing about this engine , I took a look here...http://www.stategen.com/wp-content/uplo ... ts_man.pdf
    It doesn't appear to be a very sophisticated or high-pressure oil system, so I wonder if, in fact, that "back feed" you've come across is actually the pressure-relief/bypass system. Maybe worthj looking at the pump itself as that contains a ball valve.
     
  3. lathejack

    lathejack New Member

    Thanks for the reply. I took a look on the link you gave and have done a lot of searching on the Net, and also looked in the handbooks I have but I can't find a simple diagram of the oil circuit flowing to the oil filter.

    So it is still a bit of a mystery. These engines run at 15 - 20 PSI at 1500 RPM, but it would be nice to ensure the lube is going where it is supposed to before firing it up.
     
  4. highrange

    highrange Member

    I've had a look at the manual here...http://winget.co.uk/document/LISTER%20S ... MANUAL.pdf p.23 on
    I can't say it makes it any clearer, but perhaps it'll all make more sense "in the flesh" if you remove the crankcase door .... it seems that the filter and its feed and outlet are all on the door, and connect to the rest of the oil circuit by push-fit seals (or at least that's what it looks like to me). If any of those seals are "iffy" you'd probably not be able to prime the oilways.
     
  5. JohnM

    JohnM Member

    I know nothing about this specific engine but most oil filters have a pressure relief valve between the supply and delivery ports. This is only set at a few psi. it's function is to maintain an oil flow to the engine if the filter blocks. Your pump may be overcomming this relief valve as you're only pressurising one side of it. A filter normally has pressure on both sides.
    Have you removed the plug above the filter in the photo? There may be a spring and seat in there.
     
  6. lambe

    lambe Member

    The plug I think you will find is for a pressure gauge test point.
    Malcolm
     
  7. lathejack

    lathejack New Member

    Thanks for the second link Highrange. As you suggest, it doesn't make it much clearer, but it does show it is a simple setup behind the crankcase door and so removing it won't be like opening a can of worms.

    The oil filter has a bypass valve built into it to maintain oil flow if the filter becomes blocked, and also an anti drain valve. The oil pressure relief valve would be built into the engine somewhere. The little plug is just that, a blanking plug in a threaded hole into which, as already mentioned, a pressure gauge can be fitted.

    I would expect oil to flow from the pump and into the oil filter via its outer row of holes, then flow out of the filter via its central mounting hole and onto the main bearings. Then a bleed off to the valve gear and an oil pressure relief valve in the engine exhausting into the sump. I cannot see why the pressurised oil from the pump flowing to the oil filter would be connected to the pressurised oil flowing away from the oil filter to the bearings, other than just through the filter.

    As I mentioned, with the oil filter removed, if I pump oil down the main oil way that the filter screws onto the oil just flows back out the oil way to the left that leads from the pump to the filter, and vice versa. If I block off the left oil way and continue pumping oil down the main central oil way then pressure builds up but I can hear oil slowly squelching out somewhere, hopefully the bearings and pressure relief valve.

    The link from Highrange shows that behind the crankcase door is a block with oil pipes connected to it. This block also has two holes into which fit two spigots on the rear of the door from the two oil ways leading to and from the oil filter.

    It is as if the block is just hollow allowing some oil to just flow across the two oil ways before it gets to the filter. I think any oil leaking from the spigot seals would just leak into the sump. I did wonder if Lister had added another bypass valve in there that might be stuck open, but I have found no mention of it. I certainly wouldn't expect the pressure relief valve to be there, it would be trying to exhaust oil from one oilway to another both with the same pressure.

    Maybe I should really just stop blabbing and remove the crankcase door and take a look.
     
  8. picklesquirt

    picklesquirt Member

    Good morning Lathejack,

    Having taken another look at the lubrication system on page 62 I see the pump is described as " Self Regulating Lubricating Oil Pump .Although I have no idea how this might work , is there a clue in the title and not a spring loaded relief valve as one might expect to find.
    Your last statement is probably the only solution to debug this mystery.

    Good luck
    Ewan
     
  9. JohnM

    JohnM Member

    Perhaps it self regulates it's output pressure like a lift pump does.
    Cunning idea if it does. I've never seen an engine lube pump like that but it certainly makes sense. I believe it's more common on hydraulics.
     
  10. lathejack

    lathejack New Member

    Yes I did notice that some engines have a self regulating oil pump. Thinking about it I suppose the plunger type pump may have a plunger operated via a spring. As the oil pressure increases the extra resistance means the spring will compress so that motion to the plunger is reduced.

    But the oilways are still a mystery, I can't see any reason or logic in why the oil flowing from the pump towards the filter would be linked to the filtered oil flowing away from the filter towards the bearings.
     

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