Leak down vs Compression test, Pressure Washer

[TownsendsFJR1300]

Question re a Yamaha, horizontal shaft, 300cc, air cooled pressure washer engine.

Long story short. Neighbor lends out PW, gets it back seized up solid.

I pull the Cat pump, pump is fine, oil in engine, black and nasty but there...

Add oil to the combustion chamber (OHV) and access flywheel. (still locked VERY SOLID). Found a spot on the flywheel I can smack with a 2x4 and get the engine to rotate and eventually run again.

Seems to run fine, let it warm up. Shortly later, with the pump installed, engine locks up again (from normal operating speed).

Pull the pump again, get it to rotate fairly easily this time. Crank it up, MAJOR ROD KNOCK(not there before). Verified moving the crank mid stroke with NO PISTON movement.
.
.
Now the question.

Leak down test at 90 PSI, about 6-7%, all past the rings into the crankcase (not too bad considering). (TDC @ compression stroke)

Do a compression test, max pressure 75 PSI (WOT at the carb)... ????

I would think I'd still get a decent compression pressure with the decent leak down #'s... I'm thinking a damaged cylinder below TDC???

Thoughts?


*He's likely getting a new engine ($1,200.00 machine originally) (its cheaper than a new rod, potential crankshaft damage, gaskets, etc) but I'll likely tear it down later for S&G's..

[boscoe99]

Question re a Yamaha, horizontal shaft, 300cc, air cooled pressure washer engine.

Long story short. Neighbor lends out PW, gets it back seized up solid.

I pull the Cat pump, pump is fine, oil in engine, black and nasty but there...

Add oil to the combustion chamber (OHV) and access flywheel. (still locked VERY SOLID). Found a spot on the flywheel I can smack with a 2x4 and get the engine to rotate and eventually run again.

Seems to run fine, let it warm up. Shortly later, with the pump installed, engine locks up again (from normal operating speed).

Pull the pump again, get it to rotate fairly easily this time. Crank it up, MAJOR ROD KNOCK(not there before). Verified moving the crank mid stroke with NO PISTON movement.
.
.
Now the question.

Leak down test at 90 PSI, about 6-7%, all past the rings into the crankcase (not too bad considering). (TDC @ compression stroke)

Do a compression test, max pressure 75 PSI (WOT at the carb)... ????

I would think I'd still get a decent compression pressure with the decent leak down #'s... I'm thinking a damaged cylinder below TDC???

Thoughts?

*He's likely getting a new engine ($1,200.00 machine originally) (its cheaper than a new rod, potential crankshaft damage, gaskets, etc) but I'll likely tear it down later for S&G's..

Therein lies the fallacy of the all exalted differential (aka leak down) pressure test. It does not tell the complete story about the mechanical health of a motor. It is just one of many tests that can be performed.

I would pull the head and look at the cylinders or send a bore scope down a spark plug hole for a visual inspection if you have one.

Sorry about the problem you had. I thought about loaning/renting my PW within the neighborhood but then thought about all of the damage that could occur to the pump and/or the engine.

[TownsendsFJR1300]

Therein lies the fallacy of the all exalted differential (aka leak down) pressure test. It does not tell the complete story about the mechanical health of a motor. It is just one of many tests that can be performed.

I would pull the head and look at the cylinders or send a bore scope down a spark plug hole for a visual inspection if you have one.

Sorry about the problem you had. I thought about loaning/renting my PW within the neighborhood but then thought about all of the damage that could occur to the pump and/or the engine.

Its not mine, its my neighbors he lent out. I have a commercial grade Cat Pump and it DOES NOT get lent out as the pump alone is $500.00.

I did another compression test with oil in the cylinder and the compression went up to 90 (still low but confirms the rings most likely got fried, or the cylinder).

I know the engine has a compression release which MAY be causing the issue.

Both OHV's spec out at .4mm (per spec's), cranking over, the compression release may be kicking in. It's not in the head, but in the block.

In any case, the neighbors probably just getting a new one and I'll get this one as a freebie. If the crank is still good, block not tore up, between the rod, gaskets, NEW rings, I suspect I'll part it out or sell as is.

The pump is similar to mine, BUT has a weird cable(attaches to the throttle) / valve for "idle down" which that unit itself is locked up(still available).

I have to see if this pump can be retro fitted for standard operation(no throttle down)

CAT tech dept has no idea what that part is that Yamaha added on for the idle down with this model. And its not shown (actually the pump #'s themselves won't come up)...

[boscoe99]

My pressure washer uses a cat pump but with a Honda engine. Direct drive. If the pump is pressurized there is no cranking the motor. It will act as if it is locked up. The owner's manual talks about a centrifugal clutch but damn if it seems to work if their is one.

You get one pull of the starter cord. If the motor does not start you have to pull the trigger on the hose wand to relieve the pressure. Then pull again.

[TownsendsFJR1300]

My pressure washer uses a cat pump but with a Honda engine. Direct drive. If the pump is pressurized there is no cranking the motor. It will act as if it is locked up. The owner's manual talks about a centrifugal clutch but damn if it seems to work if their is one.

You get one pull of the starter cord. If the motor does not start you have to pull the trigger on the hose wand to relieve the pressure. Then pull again.

Mine has the 9 HP Honda as well.

And yes, with the water on to the pump, the trigger HAS to be pulled or you WON'T crank it over. Knock on wood, its a one pull motor.

I'm trying to determine, if I can use the old pump without adding an unloader/regulater, I think one is built in (sent some e-mails out). Here's the same pump BUT W/O the "idle down" cable.

https://www.bphpumps.com/pd.4441/cat-pumps-3spx30g1i/

This is the pump on the unit with the blown Yamaha. You can see the "idle down" cable attached. That cable apparently goes to the throttle, senses when the trigger is pulled and increases the throttle(and pressure).

With my honda, that set up can't be used. I was told by a local shop to simply plug up the hole(bolt) and your good to go. Again, I'm not sure if I need a separate unloader/ regulator for this pump(it'd be a spare)..

<a href="http://s176.photobucket.com/user/SRT-60/media/Misc/DSCN0658_zpsmhj0b7z6.jpg.html" target="_blank"><img src="http://i176.photobucket.com/albums/w193/SRT-60/Misc/th_DSCN0658_zpsmhj0b7z6.jpg" border="0" alt=" photo DSCN0658_zpsmhj0b7z6.jpg" style=""></a>

[zenoahphobic]

I lent my Karcher pressure cleaner to my son in law's brother. (No I think he just came and took it!).

It was brand new unused and came back seized. Seems to be a global problem.

How would a leakdown test help me?

[TownsendsFJR1300]

I lent my Karcher pressure cleaner to my son in law's brother. (No I think he just came and took it!).

It was brand new unused and came back seized. Seems to be a global problem.

How would a leakdown test help me?

I've gotten several engines that were seized up and at least 50% of the time, I can get them running, decent yet.

I know on this Yamaha 300 engine, it has a 7% leak down test and compression came up from 75 PSI to 90 PSI with some oil injected into the cylinder so I know the rings (at least) need replacement (you can hear/feel) it from the the oil fill too. If the rod didn't fail, (not yet, another 30 seconds running WOT would put a hole in the case).

I've put oil down a seized 5.5 Honda horizontal engine(with PW 2,500 PSI pump), let it soak (locked solid) and slowly worked it back and forth till it came loose. Changed the oil, cleaned the carb, runs like a top! (never pulled the head, nothing). Gave it to my dad, he's still using it about 2 years later!!

Anyway, not boat related BUT Yamaha related!!

[zenoahphobic]

I'll talk about anything. My Karcher is electric! However I think the pump pressure may have stopped the motor because there probably wasn't any clutch? Relief valve?
That was related to why the petrol engine was overloaded damaging Conrod.
It was related to Yamaha as it is sitting right next to my daughters Yamaha quad and two yards from my Yam 9.9 O/b in the same shed where one of my boat with 115 Yamy O/B is stored!
I reckon if my pressure washer wasn't an electric Karcher, it could claim to be a Yamy as it is a member of my Yamy household!!

[TownsendsFJR1300]

LOL...

I got a hold of CAT and this unit DOES HAVE AN an un-loader/pressure relief built into the pump(un-like my older unit with a separate un-loader).

The direct drive pumps literally slide over the crankshaft of the gas powered units(with a key-way).

The electric units, IDK.

I'll know later today if the entire unit will be given to me. I'll bolt up the pump to my Honda and try it. Should have a spare $600 pump if it doesn't damage the engine!

[boscoe99]

My pump also has an unloader (aka pressure relief valve) but it cautions not to run the pump without water flowing through for more than two minutes time. Does yours have this restriction?

I miss my old motor/pump that had a clutch such that I could completely disengage the pump from the motor.

[TownsendsFJR1300]

My pump also has an unloader (aka pressure relief valve) but it cautions not to run the pump without water flowing through for more than two minutes time. Does yours have this restriction?

I miss my old motor/pump that had a clutch such that I could completely disengage the pump from the motor.

I think all the direct drives don't want the the engine at full RPMs WITHOUT the trigger pulled, mine included. I've had my PW probably 13 years, BUT replaced that valve at least twice along with the trigger assembly.

I just got an e-mail from CAT, that the unit pictured with that black, upright knob IS the built in pressure regulator/relief valve. I already have that idle down cable off and plugged, still waiting to hear from my neighbor. Then I'll test it on my Honda PW and hopefully NOT trash the engine...

My friend used to do commercial pressure washing, pointed me towards this machine and warned me specifically of that issue. And he is VERY familiar with the pumps, use, etc...(the Rodbolt of pressure pumps).

So I guess its a pretty common issue, thus Yamaha put the idle down cable on the pump to work with the engine(good idea actually, till the idle down part seizes up) .

That machine was manufactured in 2011 so its not that old. I did have to do a carb cleaning about 2 years ago on it.

[99yam40]

I can think of a lot of commercial business people do not knowing much about their equipment.
to them it is something you just replace and write off or send to someone to fix.
Now if he was in the repair business of these units then that is a different story.

not all of the people involved in a business are mechanically minded and work on the own stuff.
But in small ones you have to do all you can to make it profitable and hopefully you have mechanical skills.

Just stopped by a friends house this evening that has had a mowing business for years as a side, to have a look at one of his tractors that would not start.
Tested battery, starter and solenoid just by jumping around the key switch, and all work OK.

Found a bunch of wires hanging loose that he said has been that way for years and started fine in the past

Told him it could be the key switch or wiring in between. he could wire in a push button or tear it all apart to start testing and figure out where the problem was.
Showed him where to run the wires to and when pointing to the wire to energize the starter solenoid, the wire fell off of the solenoid.
Plugged it back on and all was well in his world again.

[zenoahphobic]

You have just reminded me of something.
My house garage houses all things Honda.
I keep them separated from Yamaha (too many fights!).
My 13 Hp Honda on my ride-on mower starts fine but after a while and only sometimes shuts down as if there is a thermostat. As positive as day then night. Seems to occur more when my wife uses it. It can't be predicted could go for many hours then shuts off.
Can't find a thing wrong with the bunch of wires and have been assured there is no thermal cutout - I'm not too sure.
My wife uses it to trim off pavers and stars takes and valuable plants. Handy too at rolling up fencing wire too! Chopped up my pet snake the other day as well!

[99yam40]

Has it ever done it when you were running it?
if so did you check to see if spark went away or was it fuel?

[zenoahphobic]

Has it ever done it when you were running it?
if so did you check to see if spark went away or was it fuel?

When it dies it stays dormant maybe half an hour maybe two hours, during which no spark. Then when it feels like working, turn key and fires right up again! Honda trait?