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Poppet/spool Check Valve

Discussion in 'Western Plows Discussion' started by pdqford, Jan 25, 2008.

  1. pdqford

    pdqford Junior Member
    Messages: 8

    Hello Everyone :waving:
    I'm a newbie here.

    I'm trying to get what I believe is a Western Unimount ISARMATIC plow working for a friend of mine. I've found the "Mechanic's Guide" for this plow and have been reading through the "Trouble Shooting Guide".

    I've been trying to get my head wraped around how the Poppet Check Valve works as shown on page 52 of the Mechanic's Guide, as well as on page 19 (ANGLE RIGHT - HYDRAULIC) and page 21 (ANGLE LEFT - HYDRAULIC). :dizzy:

    Can someone describe conceptually how the Poppet Check Valve does its thing?
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    The purpose of the poppet check is to prevent fluid from flowing out of the dr side angle ram while raising the plow. Without the poppet, when you shift the S3 during raise, it would open up the dr side ram passage to the resivior, allowing the fluid to flow out of the dr side ram. If you study the hydro diagram you can see how this can happen without the poppet in place.

    The poppet needs to be open though in order to allow the fluid out of the dr side ram and back to the reservoir when angling to the left (ram collapsing). The poppet is hydraulically opened to allow this by fluid pressure that's traveling to the pass side ram when angling to the right. If you look in the hydro circuit diagram, this is the dotted line going from the pass side ram passage over to the poppet check.

    Symptoms of a defective poppet check valve are:

    Won't angle left ( poppet stuck closed)
    Blade drifts left while plowing or raising ( poppet stuck open)
  3. pdqford

    pdqford Junior Member
    Messages: 8

    Thank You for the response, B&B.
    Okay. I see that on page 23. When the plow is raised, the 4-way valve (S3) shifts over to expose the criss-cross ports and the Poppet Check Valve keeps the DS angle ram from venting into the resevoir. Is the check valve function actually handled by the part labeled as 'Poppet' (on page 52) that drops vertically into the top of the block, or by the part labeled as 'Spool' that goes horizontally into the front of the block?

    Yes, I had noticed that the dotted line is darker in the 'Angle Left' diagram (page 21) than in the 'Angle Right' diagram, indicating that hydraulic pressure from the PS angle ram is being applied to the Poppet Check Valve. So is this pressure applied to the 'Spool' which shifts and lifts the 'Poppet' open, or is this pressure applied to the 'Poppet' which engages the 'Spool' and forces the Spool open? :help:
    That's where we are now. All function's work correctly except blade will not angle left, so I installed a Poppet Check Valve Kit (49226K). The blade still wont angle left.

    But if I disconnect the DS ram hydraulic hose connection it will angle left, so the Poppet Check Valve must not be opening to allow the DS angle ram to collapse. :dizzy:
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    The fluid pressure comes into the poppet cavity from the pass side ram passage and pushes UP on the vertical poppet, thus pushing the poppet pin away from the spool and allowing the fluid pressure coming from the dr side ram to push the horizontal spool valve open, allowing the fluid to flow out of the ram and back to the reservoir.

    The passage between the dr side passage and the poppet cavity could be plugged which wouldn't allow it to push up on the poppet and not allowing the dr side fluid pressure to escape from the ram.

    If you've changed the poppet assembly already and it still wont angle, the next thing to do is pull all the valves/spools out of the manifold block and clean all the passages with solvent and compressed air.
  5. pdqford

    pdqford Junior Member
    Messages: 8

    Ah-ha! So that's what moves the Poppet out of the way. :eek:
    Ah-ha again! So with the poppet pin out of the way the horizontal spool valve compresses the spool spring when the spool opens?
    Wow! I think I'm beginning to understand how this Poppet Check Valve works (but I'll have to re-read your well written explanation a few more times to be sure I've absorbed all the information imparted.:salute:
    Is there any particular solvent (brake kleen, gumout) to use or avoid?
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Exactly.. you got it now. With the poppet pin out of the way, the fluid pressure from the dr side ram can push the spool out of the way (compressing the spring) thus allowing free fluid flow back to the reservoir.

    As long as you strip the manifold clean of all valves and O-rings, you can use anything you like for the most part. Carb cleaner first, followed by some brake clean and then a good dose of compressed air works best.

    To be totally thorough you should pull the manifold off the side of the pump housing so you can clean it better and not force any contaminates/cleaners into the reservoir.
  7. pdqford

    pdqford Junior Member
    Messages: 8

    This morning I pulled the manifold block off and stripped it down of all valves, etc. (Couldn't get the Driver's Side Crossover Relief Valve plug out - looks like someone had tried to get it out once before). I thought it looked very clean inside, but flushed it out and soaked it for an hour, then used the air compressor to clean out all the passages. Reassembled all the parts and put the manifold block back on the unit . . and no change! Still won't angle left :gunsfiring:

    And if I switch the hoses it will angle left, but not right. (When I go to switch the hoses, that DS hose has so much pressure in it I have to bump the check ball in the hose end to relieve the pressure so I can it connect up the hose to the PS port.)

    Is there any special procedure to installing the Poppet Check Valve Assembly? (I installed the spool valve first, then the poppet valve, reached up in the spool valve passage with a long needle nose pliers and moved the spool and could feel that the poppet valve pin was engaging the spool valve.) I even reinstalled the old spool valve as it was not quite as snug in the passage as the new spool valve.

    Is there any way to confirm that the poppet is lifting and if the spool is sliding?

    My other thought has to do with the fact that angle left requires both S2 and S3 valves to be shifted at the same time. Since the plow will angle right I assume S2 is shifting and S3 is not stuck. And since the plow will raise I assume S3 is shifting and S2 is not stuck. But maybe when it angles left there is a problem shifting BOTH S2 and S3 at the same time. When commanded to angle left my test light lights on both S2 and S3 solenoids, but maybe there is not sufficient current to pull both valves in completely??

    Is there any way to confirm if the S2 and S3 valves are actually shifting when under hydraulic pressure? (Maybe an oscilloscope with a low amp clamp could detect the valve pintle movement?) :dizzy:
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Wait... you have a Unimount with quick couplers on the angle hoses? It shouldn't. Did some one add them at some point? Are you sure this isn't a conventional mount stye plow and not a Unimount?

    A bad quick coupler will do the EXACT kinds of things your experiencing here..

    Note: you can't attempt to angle the plow unless BOTH hoses are connected, or else the fluid in the cylinder your attempting to collapse has no where to go. Thats why its building pressure in the uncoupled hose.

    If it actually is a Unimount, get rid of the quick couplers....if this is a conventional plow, REPLACE ALL FOUR HALVES of the quick couplers.
  9. sechracer

    sechracer Senior Member
    Messages: 478

    if its a unimount, the lights and head gear come off with the blade..... Here is a few pics to help.....


  10. pdqford

    pdqford Junior Member
    Messages: 8

    I'm pretty sure it's a Unimount. (Looks like the picture provided by sechracer, and the lights and hydraulics come off with the plow - Thank You sechracer. ;) It does have quick couplers on the angle hoses, so maybe someone added them at some point.

    When I uncoupled the DS hose at the quick coupler I also took the other half of the coupler off the manifold block and snapped it on to the uncoupled hose (to keep the check ball in the hose end open), stuck the (now coupled) hose end in a bucket, commanded the plow to angle left, and it angled left, with the fluid from the collapsing DS ram spraying into the bucket. So I concluded that the DS ram, hose, and coupling were good.

    Its when I have the hoses hooked up correctly and try to angle left, that plow does not angle left, and the DS hose is very difficult to uncouple because it now has so much pressure in the hose. So I concluded that there is something in the manifold block keeping the DS ram fluid from venting into the reservoir. Thats what prompted my question about any specific procedure for installing the spool and the poppet, and a way to verify if the spool is moving or not.
    Maybe I could just remove the spool valve and see if the plow will angle left. If it won't angle left with the spool removed, then maybe S3 is not shifting and the fluid escaping from the DS ram is hitting the check valve in the pump supply passage. No, wait! If S3 didn't shift the PS ram wouldn't be under pressure to cause the angle left. :cry:
    Hmmm. But if it did angle left with the spool removed, then the problem must be in the poppet or spool, Right...er correct? (I think I'm getting a headache :confused:
  11. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    If the S3 isn't opening it'll turn right instead of left, so it has to be good...

    When you had the manifold apart did you verify that the fluid passage from the spool cavity to the right angle passage, and from the spool cavity to the S3 cavity is in fact open?

    Two things:

    Ditch the quick couplers, period. They case all sorts of strange problems...

    To test the poppet spool, remove the poppet pin and re install the plug and see if it will now angle left. Without the poppet in place to hold the spool from moving, the fluid escaping from the dr side ram will be able to push the spool open with little/no resistance.
  12. pdqford

    pdqford Junior Member
    Messages: 8

    FWIW, I did find out that the quick-couplers were on this plow and the Unimount hydraulics were adapted to it.

    Well, now that I try to recall, I think I'm gonna have to take it apart again. IIRC, the spool cavity had access to the l-e-f-t angle passage (which is the more forward hose connection on the manifold block), and to the S2 valve. I'm gonna have to get that thing apart and maybe try and get some pics.

    Again, IIRC, the DS ram connects to the manifold to the left of the spool and would try and push the spool closed. Heck, I'm just gonna have to get back on this thing and get it a part again and study it more.

    I'm also wondering if there could be some kind of obstruction within the S3 'criss-cross' portion of the four-way valve that might be keeping the DS angle ram fluid from making it all the way to the reservoir.

    Thank You again for your patience with me. I'll post again when I get back on this and get some more facts . .
  13. pdqford

    pdqford Junior Member
    Messages: 8

    Okay - I've been re-reading the "Mechanic's Guide" and these posts. I've got a couple of more questions:

    On page 20 of the "Mechanic's Guide", paragraph 4) says "Pressure within the hydraulic circuit shifts the spool, opening the poppet check valve.", so I'm thinking that the poppet pin doesn't 'hold' the spool. It's the movement of the spool that mechanically lifts the poppet pin. Does that sound right?

    Today I removed the poppet valve and reinstalled the plug and tried to angle left. No movement. Just hear the pump strain.

    So here's what I'm thinking: When I had the DS hose off and in a bucket it would angle left so I know S2 and S3 are functioning to get the hydraulic pressure from the pump through the 'criss-cross' in S3 and through the shifted S2 and on into the PS angle ram. And when I had the manifold block apart last week I could see that the return port from the DS ram had access to the poppet chamber and the poppet chamber had access to the S3 chamber. (I think :dizzy:

    What I couldn't verify was that the exhaust path though the S3 'criss-cross' was working (but I was able to put a small screw driver in the end of the S3 valve and feel the internal spool push in and spring back, and I estimate that it moves the specified .070") How does that S3 valve pass the exhausting fluid from the poppet chamber? Is it possible to disassemble that valve?

    I also need to verify that the manifold block is open between the S3 valve chamber and the main housing. Where the three o-rings are located between the manifold block and the main housing, I can see that the middle o-ring is where the hydraulic pressure comes out of the main housing and into the inlet check valve. Is the higher o-ring the passage from S1 to the lift ram and the lower o-ring the exhaust passage from S3 to the reservoir? Or do I have them reversed?

    But wait! Since the exhaust path from the S3 chamber to the reservoir is also used when the plow is lowered, and the plow lowers fine, that path must be open.

    But when the plow lowers, S3 is not shifted. Only other time S3 is shifted is when the plow is raised. Hmmmm, but the raise function doesn't use the exhaust portion of the 'criss-cross'. Only thing that uses the exhaust portion of the S3 'criss-cross' is angle left!

    Anyway to prove that the exhaust portion is failing without having to through a new S3 at it?

    P.S. Thanks for having the patience to listen to my rambling . . . Jim
  14. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Do you clean the S3 with brake clean and blow compressed air through all the port with the valve shifted?

    Can't ever remember having just the exhaust port plug up on a 4 way valve, but anything's possible when dealing with hydro's...

    Test the poppet again, but this time leave the spring out on top the poppet pin (leave spool and pin in) If it still wont work then it's not a poppet problem as far as the poppet assembly itself, but could still be a restricted passage.

    Did you ditch the quick couplers?
  15. pdqford

    pdqford Junior Member
    Messages: 8

    Good point! I did soak the 4-way valve and blow it out with compressed air, but not with the spool inside the valve shifted. I'll give that a try next time I get a chance.

    IIRC, we have tried to angle left with only the spring removed, and with both the spring and the poppet removed.

    Negative. Owner wants them left on there, but when it won't angle left, you have to be careful when you go to remove the poppet plug as it has some residual pressure behind it, so I'm (pretty?) sure that the quick coupler is not currently acting up.

    Okay - I'll post up with what I find next chance I get. (This thing is really turning into a mystery to me and I can't seem to let it go . . . . . and I'm turning into the :jester: