Bucket tilt lever controls lift arms? Ford 3400 / 730

Midniteoyl · May 20, 2013

Hey guys.. I have a Ford 3400 with a 730 loader. When I first got it, the lift and bucket cylinders leaked down fast due to multiple external leaks (lines, cylinder caps, etc). I have tightened/fix all those and now the bucket holds unloaded, and drops slowly loaded, and the lift arms still drop, but slower than before. Ok, still a leak somewhere, possibly in the cylinders, right? Well, while playing around, I found that the bucket tilt control will actually raise the lift arms. Tilt the bucket back and the lift arms slightly raise until the bucket is full back against the stops and then the arms go up fairly quickly. Even hits the pump hard enough to activate the governor and idle up the engine.

So, question is, is the indicative of a leaky cylinder (bypassing?) or maybe a bad controls in need of rebuild? Both?

Thanks guys..

Midniteoyl · May 21, 2013

Crickets.... chirp.... chirp...

hazmat ranger · May 22, 2013

My $$ is on valve.

Harry in Ky · May 22, 2013

If you want answers, you need to explain more about how the loader is plumbed to the tractor. Does the loader use flow from tractor remote valves or is it a separate valve with oil supplied directly from a port on the tractor? If it's a separate valve entirely, then it needs to be a power beyond capable unit, with three hoses to and from the tractor, not two. If it's plumbed with two hoses, the return most likely feeds into the lift system and that's where the problems come from. This can lead to many strange things with lift system.

Midniteoyl · May 22, 2013

Not sure what you mean.. its a dedicated front pump powered off the crank and pulls/returns fluid to the loader frame which doubles as the reservoir. It is a 'center open', 2 line system, if that means anything..

Thanks

Midniteoyl · May 22, 2013

hazmat ranger said:
My $$ is on valve.

Thanks.. kinda thinking that too..

Harry in Ky · May 22, 2013

If it's a totally separate system, how does it have anything to do with the lift arms? What exactly are you asking about?

Farmerford · May 22, 2013

I agree with Hazmat Ranger and Midniteoyl: it is most likely the valve.

The boom spool is not completely blocking the boom work ports in neutral. The up work port is slightly connected to the pump bore in the valve. However, until you also shift the bucket spool the pump flow is free to flow through the pump bore, out of the valve, and into the tank; there is no pressure build up in the valve that would force fluid through the partially open boom up work port.

But since the boom spool and bucket spool are (almost certainly) in parallel, when you shift the bucket spool from neutral it both connects the pump flow to the bucket work port and blocks the exit of pump flow from the valve pump bore. Both actions are necessary: the bucket work port is exposed to the pump flow, but nothing will flow into the bucket cylinders until the flow of fluid out of the valve body is blocked; that builds up pressure in the pump bore to force fluid through the connected work ports.

When you first shift the bucket spool, particularly if the bucket is empty, there is very little pressure build up because the bucket cylinders move to accept the fluid flow; therefore, there is little pressure forcing fluid through the partially open boom up work port and the boom rises slowly. But when the bucket cylinders reach the stops, the fluid has nowhere to go other than into the partially open boom up work port; therefore the booms raise more rapidly. When the boom cylinders extend fully, there is no place left for the fluid to go, the pressure rises further, and the relief valve opens.

The failure of the boom spool to block the work ports in neutral may be due to trash in the valve, a defect in the spool itself that is just now showing up (unlikely), or most likely a worn or broken detent/spring that should hold the spool centered when in neutral. Try slightly shifting the control lever for the boom spool while fully shifting the bucket spool. I'll bet if you shift the boom spool one direction the problem will worsen and in the other direction it will get better.

Let us know what you find.

Midniteoyl · May 22, 2013

Thanks Farmerford! Exactly what I was looking for!

Try slightly shifting the control lever for the boom spool while fully shifting the bucket spool. I'll bet if you shift the boom spool one direction the problem will worsen and in the other direction it will get better.

This is the exact behavior. Although I can slightly hold the bucket control and hold both the bucket and arms in position.. So, best bet is the centering/detent spring? That would be a huge relief..

Jim