Fast Dump Not so Fast?

[MRCONCDID]

My 7308 loader has a 2 step dump there is a 3-4 second pause before the bucket starts to move and really doesn't dump any faster than the regular position. I have adjusted the pressure relief valve up which i would think it would make it even faster but it didn't, it did make the lift and breakout stronger/faster but not the fast dump. also i get a loud squeal/honk sound when the relief valve trips.
I adjusted it about an 1/8 to 1/4 turn out just enough to pick the front tires up with the arms not the bucket when the bucket is flat on the ground.I do not know what pressure it is.
could I be pushing to much pressure through the FEL controls? even with no relief valve installed the pressure would only be the same as the pump puts out around 2,000 psi.
any thoughts would be helpfull.Thanks

 

[Soundguy]

Turning up a relief does nothing for system speed.. it merely changes the top end limt where the relief operates. flow rate ( speed) is a function of pump displacement, engine rpm, and hose sizes, and cyl sizes.

pressure and cyl size determine strength.. relief determines upper pressure limit.

many ag setup use 2500 psi for main pressure, and a little less for add on equipment.. that way the relief built in to any add on equipment pops befor ethe main system relief ( if the add on has it's own relief.. etc. )

and yes.. relief valves squal or vibrate when they start venting.

I'd slap a gauge onto a remote and then get to setting my system back to factory specs, if it has been increased beyond those.

soundguy

 

[MRCONCDID]

I agree I need to put a gauge on it. My real question is it normal to have a 2-4 second delay between fast dump and normal dump?

 

[jinman]

I never see much more than a 1-sec delay of my bucket when it goes to the fully dumped position and then is driven to its maximum dump angle as the hydraulics catch up. That's with a full bucket of dirt. The bucket dumping is quite fast enough from the time I move my joystick to the full regen position until the curl rotates and dirt falls from the bucket.

Of course, my loader is a 16LA and has many differences to the 7308 including a tractor hydraulic system with much more flow.

Dumping a bucket is subject to a lot of variables. Is the bucket full of dirt? Is the engine's rpm above 2000? If you are just exercising an empty bucket, it may have very different characteristics than if the bucket is full and you have the full load of dirt assisting in the dump action. At those times, it is almost common for there to be a momentary delay between full dump and the time the hydraulic flow catches up and provides additional bucket movement. Three or four seconds would be a huge time delay for that. Are these "seems like" delays or measured with a timer? We can't see your bucket's action here, so when you say 4 seconds, I say to myself, "one-thousand-one, one-thousand-two, one-thousand-three, one-thousand-four." Whew! That's a long time. If your bucket is delayed that long, I'd be looking for a problem too.

 

[Doloe]

I'm experiencing the same issue with that loader on a TC-30.
The delay wasn't there when I got the tractor.
I haven't gotten around to trouble shooting so maybe I'll get lucky and someone will post the fix.

 

[Stonehaller]

I am not familar with the control on the 7308 loader, but is there linkage or cables between the lever and valve that could be out of adjustment so that the valve is not actually getting to the full regen position?

 

[MRCONCDID]

I honestly have not taken it apart yet, it looks like its all internal so I wouldn't think linkage but who knows. the pause feels only to be in the fast dump not it the slow dump with or with out dirt in the buckets, the pause is longer with an empty bucket but still there. so you might be on to something about the hydros catching up. I will count the mississippi's the next time I use it.

 

[kennyd]

I agree I need to put a gauge on it. My real question is it normal to have a 2-4 second delay between fast dump and normal dump?

I never see much more than a 1-sec delay of my bucket when it goes to the fully dumped position and then is driven to its maximum dump angle as the hydraulics catch up. That's with a full bucket of dirt. The bucket dumping is quite fast enough from the time I move my joystick to the full regen position until the curl rotates and dirt falls from the bucket.

Jim's comment about the bucket being full is key here...your fast-dump , or technically called the Regenerative function of the valve should only be used with a full bucket. If you are trying it with a empty bucket then the delay is expected because BOTH sides of the cylinder are getting pressurized the the "fast-dump" position.

Read the first post in THIS thread for a great explanation.

 

[Stonehaller]

If you are trying it with a empty bucket then the delay is expected because BOTH sides of the cylinder are getting pressurized the the "fast-dump" position.

Using regen with an empty bucket should not make any difference. You will not see a delay with regen because it is pressuring both sides of the cylinder unless there is an air pocket in the back side of the cylinder. If the cylinder is full of oil when you apply regen to dump, then even though you are applying pressure to both sides, the pressure differential, due the different areas between the rod side and back of the piston, is there instantly and the cylinder should extend without delay.

If there is an air pocket on the back side of the cylinder, then regen will have a delay as the pressure applied to the rod side of the cylinder will not let the weight of the bucket assist in the dump until the air pocket is compressed on the back side of the cylinder. The cylinder has to actually starting moving before regen is of any benefit.

The hydraulic pump is mostly likely not producing enough oil volume to keep up with bucket when you dump without using the regen even if the bucket is empty. If the cylinder moves faster than the oil can get in you end up with a vacuum in the cylinder. Not really a hard vacuum as the oil will outgas dissolved air in the oil and fill the void. Anyway, you end up with an air pocket in the back of the cylinder.

Try dumping, with regen, and curling your bucket several times to get rid of any air pocket and see if that eliminates the delay.

 

[dqdave1]

Make sure your RPM is up, and check all lines for kinks, or bends that may cause oil restriction. I would disconnect and reconnect the disconnects also, to make sure they are fully seated. A slight delay is normal.
Also check oil resevoir to make sure it is full.