Power Loss

[KurtBP]

Hello, I just bought a 2006 Bobcat 430 ZHS Mini Excavator. Everything on the machine seems to work very well. My operating was using the machine a few days ago and we noticed the following:

1. If you are trying to go up a muddy incline, and you use the boom and stick to pull the machine forward while also tracking forward the machine drops its rev and it gets to a point where it almost cuts off the engine. How , if you track only or if you pull only the machine will not do this.

2. If there is too much of a heavy load in front of the machine and you try pushing it with the dozer blade, the machine drops its rev and it gets to a point where it almost cuts off the engine if you continue tracking forward.

When this happened, I changed the air filter, the water/fuel separator, the fuel filter, I topped up the hydraulic fluid a bit and still no change.

I am very new to this whole excavator world and so I am very concerned about the investment that I just made. Please give me some guidance.

 

[02Dmax]

Sounds like a hydraulic issue. Can you drag the rpms down just digging with it?

Just to be safe it'd be worth the time to make sure the fuel tank is clean and the supply fuel line isn't collapsing or disintegrating internally.

Sent from my SPH-L710 using Tapatalk 2

 

[Delmer]

Try to get a feel for how much smoke is normal when you put a good load on the engine. If it's not making smoke when it's stalling, I'd be looking at a fuel starvation issue. If it stalls while it's blowing the blackest smoke it ever does, then look at the hydraulics.

 

[KurtBP]

Thank you Dmax for you response. No the rpms dont go down when I am digging with it.

Delmer, it does not make any smoke when it is stalling. If its a fuel starvation issue, where would you advise that I start looking. Fuel filter is new and water separator is new as well.

 

[KurtBP]

Does anyone have any other ideas that I can try ? Please assist. This is a really big problem for me.

 

[02Dmax]

Did you check the fuel supply lines? Could have low fuel pressure, bad lift pump or something else.

Sent from my SPH-L710 using Tapatalk 2

 

[Delmer]

Apparently that's a Kubota engine so I can't tell you anything about the injection system, but you can put a tee in the fuel supply line right before the engine and run a line into a pressure gauge in the cab and see if it's maintaining the same pressure when it stalls as when it's running at the same speed with no load. Or open up the filter right after it stalls and see if it's under pressure or suction, and if it's full or if there's air in there.

Clogged fuel lines, pickup tubes, screens in banjo bolts, elbows, transfer pumps...???

 

[KurtBP]

I did check the fuel tank it is clean. I also checked the fuel lines and they are clean. I didn't check the pump, because I didnt know what to check for.

 

[KurtBP]

The funny question is why is it only doing this when the machine is under some pressure ? Why is it not happening when the machine is operating normal ?

 

[02Dmax]

You're going to need a pressure gauge, some t fittings to use the gauge, and a general knowledge of the fuel system you have in order to fix this.

Sent from my SPH-L710 using Tapatalk 2

 

[KurtBP]

I will work on getting the fuel gauge and the necessary fittings. Do I connect the gauge before or after the fuel filter.

 

[Delmer]

It happens when the engine is under load because the engine is using more fuel, the "restriction" lets enough fuel through to run the engine with moderate load, but not enough to run at full power.

Hook the gauge either place, it will tell you different things. I said tee in just before the injection pump, because if that pressure is good then you know the problem is in the injection system, not before the tee. You want a low pressure gauge, ideally a vacuum and pressure gauge. If you don't have a vacuum gauge available, you can run the line and use a "squirt" test, plug the line with a bolt and see how it squirts when you pull the bolt out, then compare that to how it squirts when it's stalling.

I'd study the fuel system a little more so you can tell where the fuel goes etc. Does this have a transfer pump with priming lever/pump?

 

[KurtBP]

I must say that I have not tried the last few suggestion that you guys suggested, but I am really thankful and greatful for you taking your time out to assist. I really means alot. I am glad I came across this forum. There is alot of great advise on here.

I will try all of the suggestions and I will keep you guys updated. In the mean time if there are any more ideas, just keep them coming. I was reading somewhere that Bobcat had issues with their Fast Track System which may have been causing this. Is there any truth to this ?

 

[KurtBP]

A friend of mine suggested that I change my lift pump to a slightly bigger pump. Can you please give me your opinion on this ? Will it cause further problems down the line for my machine ? And if indeed I can use a larger pump, can I use a pump for a Bobcat 435, if not what size pump would be adequate.

I would also like to know the part number for the 430 lift pump and also the part number for the 435 lift pump. The reason is depending on the responses I get I will have to get either of the pumps from NAPA.

 

[KurtBP]

Any help please guys ??

 

[mitch504]

Ok, ignore that friend.

1. Transfer pumps move way more fuel than can be pushed through the injectors. The considerable overage is used to lube and cool the injectors and injector pump, then returns to the tank. It is not unusual to have more return than is burnt. Just more horsepower from the same engine will use the same transfer pump.

2. If you start throwing parts at a machine instead of doing the work of testing you are just blowing money. A lot of non-mechanics, and some dealerships do it this way, because it isn't their money.

3. Do you really think the engine manufacturer puts inadequate pumps on all their engines and nobody has noticed until now?

 

[mitch504]

I expanded on my earlier flippant answer, above.
Sorry,
Mitch

 

[willie59]

If there is too much of a heavy load in front of the machine and you try pushing it with the dozer blade, the machine drops its rev and it gets to a point where it almost cuts off the engine if you continue tracking forward.

I think this is an important symptom. Doing this operation, the digger isn't involved as your first symptom indicated as in going up a muddy slope while using the digger as an assistant. Using the blade to move material and causing the engine to stall is solely related to the drive.

Sadly I have no experience with the Bobcat 430 so I can't offer any advice that can be considered spot on. However, given the info you've submitted, and that the problem seems to be isolated to the drive functions. Yes, I've heard myself that the Bobcat Fast Track has been known to have problems. Just what problems for sure I don't know, like you it's just things I have heard. Additionally, leaving aside problems with fast track, I wonder if you have a problem in the rotary joint delivering oil to the drive motors. There is a possibility that you have a seal failure in the rotary joint causing both lines to the drive motors to receive pressure from the pump causing a stall. But again, that's just a suggestion as I know nothing about this machine. But what I do know, I agree with Mitch about a bigger lift pump, ignore that friend, that's not a solution to your problem.

BTW, welcome to HEF. :drinkup

 

[KurtBP]

Thank you very much. In view of your advise, I will ignore this option completely.