Echo SRM 260 Leak Test Pressure

Discussion in 'Mechanic and Repair' started by ed2hess, Oct 11, 2017.

  1. ed2hess

    ed2hess LawnSite Fanatic
    Messages: 14,370

    Having trouble getting one of my very old ECHO SRM260 going. It has about 110 psi compression so that should work. New coil and carb....Got leak test set up and it holds at 40 psi? Little afraid to go higher might blow out seals???..........how high should I test?

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  2. ricky86

    ricky86 LawnSite Silver Member
    Messages: 2,092

    First off, you have the hose hooked into the vacuum port. I cant believe that plastic pump can build that much pressure. Stihl products, when testing, only have to hold .5 Bar. 1 Bar is approx 14 psi. Positive or negative.
    For approx 20-30 seconds. I leave it a little longer.
    Of course, before you did anything, you removed the muffler to inspect the piston. And also inspected the intake port, because a compression gauge is useless for a 2 cycle.
    You ALWAYS do a vac test first. Seals leak mostly under vacuum. The pressure test wont show a seal leak.
    Just the opposite. The pressure will make them seal. The pressure test will show broken insulators, leaking gaskets etc.
     
  3. ed2hess

    ed2hess LawnSite Fanatic
    Messages: 14,370

    As it is hooked air comes out that port:dizzy: hooking to port on top seem to be suction port:dizzy:. But vacumn part of pump not working..Compression test does tell you a lot ...as posted this unit is about 100psi and that should be good enough. Rings are fine not stuck. What will vac test tell ???
     
  4. ricky86

    ricky86 LawnSite Silver Member
    Messages: 2,092

    Compression gauge will NOT tell a lot. A compression gauge is used for comparison of cylinder to cylinder. I’ve seen saws with 100 psi with wiped out cylinders. They wont run that way. If you didn’t look in the ex port, you don’t know the condition of it. Suit yourself.

    Vac test is to check seals. If you pressure test a seal, the pressure will cause the lips to push down, which makes them seal. If a seal is bad, usually it will leak as the piston goes up, which creates vacuum in the crankcase causing the seal to lift causing a leak. Try and compehend the theory before you pass judgement on any of my advice. Beleive it or not. Again, don’t care.

    I have the exact same MityVac pump. The pressure port is on top. The vacuum port is in the front. I have a picture from the owners manual stating that. I use mine almost ever day.
    You seem to have your mind made up which is fine. Just remember that every action has an offsetting reaction. If air is sucked in, it has to come out somewhere.

    And the gauge picture you posted is reading kilopascals. Not PSI. 40 kilopascal is approx 5.5 psi or when related to vacuum approx -8.

    That pump, and the SilverLine for that matter CAN NOT create 40 psi. Never, ever. Regardless of what you think.







     
  5. ed2hess

    ed2hess LawnSite Fanatic
    Messages: 14,370

    Thanks.......I hadn't used this for a long while. I will reset my mind and look at from what you explained. I have looked at exhaust port ....I had the head off when I put in upper piston bearings...new rings groves cleaned a few years ago. A week ago I discovered new coil was mounted wrong. After changing that the unit started and ran. With new carb the unit is hard to start but top end rpm fine. When they start hard I go to seals but all are new....unit sit 4 years. I do thank you for taking the time to set me straight.
     
    hort101 likes this.
  6. ricky86

    ricky86 LawnSite Silver Member
    Messages: 2,092

    Yanking the muffler isn’t that difficult and can save hrs. I work on these things everyday bloody day, and get fooled sometimes. Having a consistant trouble shooting procedure is the way to go. The owners manual for that pump is online. Just google it. Learn how it works. Very versatile tool. You can check a chitload of things with it. Engines, cap vents, tank vents, fuel pumps, primers, inlet needles, check valves. You get the idea.
    I use silicone spray into the vac end. It lubes the valves and plunger. The vegetable oil they recommend gums thing up.
     
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  7. ed2hess

    ed2hess LawnSite Fanatic
    Messages: 14,370

    Pulled the head off had a small leak at the gasket. Exhaust port clean. Noticed that the gasket partially covered transfer port. Looked at another gasket and it was cut with tear drop opening so I will change.

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  8. fritowrdo

    fritowrdo LawnSite Fanatic
    Messages: 7,995

    Always love your posts Ed!
     
  9. ed2hess

    ed2hess LawnSite Fanatic
    Messages: 14,370

    Got my new minivac and tried it on a carb that was leaking gas onto fender of trailer. Thought this would be slam dump:rolleyes:. Hooked into fuel inlet and it held 8 psi:dizzy: then hooked to primer outlet pump and hold several times seem okay:dizzy:. How do I test that little white colored vent asy on third line going into gas tank?

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    I hooked to primer outlet to do pump and hold about 4 times.
     
    hort101 likes this.
  10. ricky86

    ricky86 LawnSite Silver Member
    Messages: 2,092

    If the cap isn’t vented, the tank vent “should” vent in. I’m not positive. We don’t work on echos
    If it does vents in, tighten fuel cap, apply vacuum to the fuel line after plugging the primer return line. It should bleed down slowly. Apply pressure and it should hold. If it bleeds down with pressure, use soapy water to find leak.
    No more than 7 or 8 psi. Positive or negative. If the cap leaks test wont work. If there’s any residual fuel in the tank, you will ruin the pump. Apply compressed air the tank to dry it.
    If fuel is sucked into pump,flush immediately with vegetable oil, then lube with silicone. That’s explained in the owners manual that you should have read already.
    You have know how the vent works first. Does it suck in air or blow off pressure.
     

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