Branson 3510, perplexed by fuel delivery issues

   / Branson 3510, perplexed by fuel delivery issues #1  

thorsent

New member
Joined
May 25, 2012
Messages
9
Location
Charlottesville, VA
Tractor
Branson 3510
I have a Branson 3510 with about 250 hours on it. Earlier in the week I was mowing the lawn and after about an hour or so the engine suddenly got weak. Went down to a very rough idle with no power to move or run PTO. Never quite stalled out.

Hadn't run it most of the winter so I figured most likely was bad gas, and time to change the fuel filter anyway so I drained the tank. Unfortunately I just couldn't get the fuel bowl cap off given how tight it was and the angle of installation (strongest man in Korea...) so I had to remove the fuel bowl assembly and get it into my garage vice. Ended up using a plumber's wrench to loosen the cap. Replaced the filter and noted that the top lip of the plastic fuel bowl had snapped off, so ordered a replacement Yanmar part ($20 for plastic...) and then set off to put it all back together.

I filled up the bowl with diesel, reassembled, remounted, added a few gallons of diesel back to the tank, and for good measure, before reattaching, I filled up the intake hose that connects to the fuel pump (assuming that's the fuel pump mounted to the side of the engine with the injector tubes coming out).

I opened the forward bleed screw on the fuel filter housing and cranked but nothing came out. Hmmm. Tried a few more times. Also warmed the glow plugs to see if the engine would start but it wouldn't catch. Not even a sputter.

So then I closed that screw and opened the bleed nut on top of the fuel pump. Cranked the engine expecting fuel to come out. Nothing. Took the bleed nut all the way out. It was moist in there but no sign of much gas.

Now I'm out of my element and after years of reading TBN and finding my answers I'm finally posting. Shouldn't fuel start coming out of the bleed nut above the pump? I cranked many times, probably a few minutes if you added all the attempts. Perhaps given that everything was disconnected I'm just haven't gone far enough.

I should note that after opening the bleed nut I did try starting again and there was the faintest of sputters but then after a few cranks even the sputter went away.

Advice sought. I've got the weekend coming up with sunny weather so I'm ready to tackle a bigger job if need be.
 
   / Branson 3510, perplexed by fuel delivery issues #2  
When you turn the key on can you hear the electric lift pump run? It sounds like the pump is not working.
Others have posted that they used after market low pressure pumps from the parts stores.
 
   / Branson 3510, perplexed by fuel delivery issues #3  
not mentioned was if you turned the fuel shut off back on? What else you could do is to fill diesel with a funnel through that bleeder screw hole on top of the fuel pump until it is full. Then try start the engine again.
 
   / Branson 3510, perplexed by fuel delivery issues
  • Thread Starter
#4  
@Stimw. Will check tomorrow. Do you mean can I hear it when cranking or would the motor be running with the key in run position?

@DieselMonk. I'll try that. Stupidly I put all my diesel in the gas tank. I had saved a little in a cup which I used to fill the intake hose. I had a little extra in the cup. A few minutes later after I opened the bleeder I had the same thought, let me pour some fuel right in there. I went to get the rest of the diesel out of the cup but it was gone. There was a tiny hole in the bottom of the cup...

I'm realizing now that likely the bleeder valve I had opened expecting fuel to come out was actually the injector pump. Injector pump is between filter and engine, fuel pump is between tank and filter?

I was confused about the fuel shutoff lever. The markings are in korean. I have it pointed down which I assume is on, however I also cranked a few times with the switch in either setting as a sanity check (and also 90 degrees which would be certain to let fuel through).
 
   / Branson 3510, perplexed by fuel delivery issues #5  
To test your fuel shut off, take your bowl off again and let the diesel from the tank into a clean gas can. You will see if fuel keeps coming or not and test your fuel shut off. Once you figured out how the shut off works, close it, and fill the tank to the full mark with diesel, install the fuel bowl but not tighten it. Then open the fuel shut off valve and the bowl shoud rapidly fill itself. Once all the air escaped, tighten the fuel bowl.
Next: With the ignition off!!! give it full throttle and open up the injector pump bleeder screw. Let the fuel run until all bubbles escaped and close it. Don't forget to take the throttle back and start it. If she still doesn't give any fuel, then check the 12V fuel shut off solenoid on the injector pump. It may be broken, stuck, or not receiving any voltage at all. Maybe check that first and even tap it carefully with a hammer.
You may have a fuel pump between the bowl and the tank and check it if it works. Maybe it is plugged with garbarge or doesn't even work. Maybe there is even another filter installed that is full of garbage. If you have a fuel lift pump, it shoud work as soon as you turn the key once click without glowing or starting the engine.
 
   / Branson 3510, perplexed by fuel delivery issues #6  
Because the Branson has the fuel tank located below the floor they use a lift pump to the filter .
When you turn the key on you should hear the pump run before you try to start it. If your lift pump isn't working fuel won't get to the engine after you drain the filter and let air into the system.
 
   / Branson 3510, perplexed by fuel delivery issues
  • Thread Starter
#7  
Thanks for the help so far. Things are much clearer now with the clarification on the lift pump.

I went ahead and poured a little fuel into the bleeder nut fill on the injector pump. The engine did turn over and idled roughly for a handful of seconds. Then it died. So that at least confirms fuel delivery problems.

Next, I determined the fuel shutoff valve location. Rather simple actually. I disconnected the hose at the lift pump and then with a straw I filled it up with fuel. Then I turned the bleed screw on the fuel filter and watched as the fuel got sucked into the bowl and air bubbled out the bleed. So "down" is open, which makes perfect sense since the only way to remove the bowl is when the valve is in the up position, closed.

Next I started listening for pump action. At the time I thought the lift pump was the fuel pump, and I heard nothing. I confirmed that it was getting 12v at the plug.

Then I decided a sanity check would be to leave the hose disconnected between lift pump and fuel filter. Crank the engine and fuel should spit out of the hose. Am I right about this? Doesn't seem like I could come up with a more basic test. Suffice it to say that no fuel came out so I suspected the lift pump was dead.

I disconnected the pump and took it into the garage. Hooked the leads to a 12v battery and there was no action. I'm assuming there should have been action if the pump were functional but I don't know perhaps there's a vacuum actuator or something. Please let me know if you think this is a valid test.

Finally I took the pump itself apart. Nothing much going on inside there. Certainly nothing obviously broken or disconnected but then I have no idea what's going on with the wiring since it's all encased in hardened plastic.

At this point I'm assuming I have a bad lift pump. Again, if you think I've made a bad diagnosis or can suggest another test then let me know. Also please feel free to recommend a vendor where I could purchase a replacement. Seems like a pretty generic part.
 
   / Branson 3510, perplexed by fuel delivery issues #8  
I am not a Branson tractor owner, but I do know that a few Brasnson tractor owners had the very same problem. They got their lift pump / fuel pump replacement from Nappa. Bleeding should be very easy with a new lift pump! ;) You diagnosed correctly!
 
   / Branson 3510, perplexed by fuel delivery issues
  • Thread Starter
#10  
Conclusion

I wanted to thank everyone that helped with this issue. The problem did indeed turn out to be the lift pump. As suggested I went to NAPA to look for a universal pump but they did not have anything with the right type of electrical connector, nor did they have anything in stock that was low pressure. So I bit the bullet and drove over to the Branson dealer to get a bolt in replacement. It cost twice as much as the universal model, and given the poor life span I will probably end up paying it over again in the future, but at least it was a bolt in.

At the counter I placed the old fuel pump on the counter. Disturbingly, the clerk simply went to the back of the store and plopped a new one in front of me. No need to ask model or anything. He knew from experience, said it was a "popular" replacement item... At the counter was an old timer. He said it was a blown circuit board. I popped off the black plastic and sure enough you could smell the burn. Old timer winked and bid me good luck.

Replacement of course was dead simple although tedious requiring 1/8 turns with a long box wrench. Kind of glad to have the bolt in replacement in this situation. As for bleeding, what I did was use a drinking straw to pipet fuel into the intake hose. Then I'd open the bleed valves and wait for the bubbles. Pipet some more fuel. etc. This worked well. Nice way to do it as a one man job, without grinding down your battery and/or without a hot engine inches from your fingers.

Sure enough, with the new lift pump, turning the key to run position caused it to start up with an audible whine. I had just never paid attention to this in the past but now it's plain as day. The lesson here, if you don't hear the audible whine then it is the lift pump. No need for guessing.
 
 
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