Bobcat 863 (and similar) fuel lines/tanks

[Defender]

WHAT I'VE DONE: My Bobcat 863 (year = 2000 with about 2300 hours) quit running with ¾ tank of fuel. I replaced the fuel filter and the fuel riser pump. I couldn't get the hand-squeeze bulb (also replaced) to pull fuel up into the fuel pump and filter. I filled the tank with the bulb removed until fuel spilled out the open fuel line. I reconnected the bulb, pumped it, bled the injector lines, and she started right up.

WHAT I SUSPECT HAPPENED: If the fuel line that goes down into the top of the tank were to have broken off, then when the fuel level got to ¾ of a tank, I assume that the Deutz engine's fuel riser pump would then start sucking fuel tank "air" and the engine would quit. Also the hand-squeeze bulb would probably not pump anything but air. Filling the tank would get the level up above the broken internal fuel tank line.

HERE'S MY QUESTION(s): Does this sound reasonable as a source of my engine failure? Is there a way to test this short of pulling out the fuel line to check it visually? As the fuel is sucked down during use, where does the fuel tank get its replacement air so that it does not pull a vacuum? Is there a one-way valve on any air intake line to the tank?

(this is my first post, so I'm anxious to see what kind of response I get here -- thanks in advance)

 

[willie59]

Welcome to HEF Defender. You're spot on with your diagnosis, very common problem on Bobcat machines to have fuel pick up tube in tank broken off. The result is exactly what you describe.

 

[Delmer]

Yes, that's the most reasonable source of your failure. common problem, search for "bobcat fuel pickup tube heavyequipmentforums" and stay up late.

If your sucking air out then that's pretty clearly the problem. Usually the cap has a breather, not positive on bobcats.

 

[TriHonu]

Willie did a repair write up on it HERE

 

[Defender]

Great confirmation guys. This is a great forum I've found here. I'll try to "pay back" as I have opportunity. I'm going to pull the fuel tube and inspect it to see if the surmised problem is indeed THE problem. I'll let you know if it turns out to be so.

 

[Defender]

Here are the results!

OK, here are the results!

Buried deep within the inaccessible belly of the Bobcat is the fuel tank suction elbow. *A tube with a filter end swings freely within the tank to suck up the diesel. *As you know, that is a bad design in that the tube often fatigues and fails. *Well, one new fuel riser pump later and a month of the loader sitting in the woods, its back in the workshop where I was able to remove the grouser tracks and the right rear tire to get to the rear side access panel. *Removing the panel reveals the top of the fuel tank with the fuel level sender, and three other hoses (the injector overflow return, a larger hose that looks like some kind of air pressure equalization hose, and the fuel source hose to the fuel riser pump).

Cutting the fuel source hose at the elbow which goes through the tank top grommet allows one to reach in to about the center of the machine to pull out the elbow and grommet. *Praise God, after all of this trouble, when I removed it, I found that the internal hose was indeed broken off such that if the tank were COMPLETELY FULL, fuel could be sucked up by the riser pump, but as soon as it got about 1 inch down from the top, the pump would suck air. *

So for those with 863 Bobcats, you don’t have to raise the cab, you don’t have to pull the engine, just go into that right rear side panel. *While you’re in there, and before you pull the grommet, clean everything out so no junk falls down into the tank. *Also, while you are doing this, go ahead and replace the fuel line from the tank top elbow to the fuel riser pump. *Bobcat of Atlanta tells me that this hose is 29.5 inches long. *That sounds too short, but I’m going to thread a new one in while its “easy” to do.

Bobcat should either make a better hose or (as I am considering to do on my machine) extend the vertical (down) end of the elbow with a (strong, non-fatiguing) metal extension of several inches. I may braze one onto my elbow. Why? Because were the hose to fatigue and break off again, it would do so at a fuel level that is several inches down from the top of the tank. If the loader quit some distance from the house out in the woods like it did this time, I could refill the tank, prime the pump and fuel filter (hoping that the injectors didn't get air in them, lest I have to crack and bleed those), knowing that I could go for a good distance-- even with fairly steep slopes-- and make it back to my indoor workshop without the Deutz engine sucking air and quitting. EVERYTHING is harder to do when you have to do it in the field!

 

[Defender]

EXTENDED ELBOW

Per my pervious comment about extending the vertical drop of the Bobcat elbow to guarantee suction to a greater depth within the tank even if the flexible tube breaks, the following picture is my solution...

 

[willie59]

Slick work there Defender.

 

[Defender]

THE FINAL STEPS

To finish the job, I purchased the a fuel tube from Bobcat that is not supposed to deteriorate or fatigue like the older hoses in some machines. Actually, the hose that they gave me looked like it was made of the same fatigued material that I pulled off the elbow originally. Anyway, this is a stiff plastic "tube" rather than a hose. Its consistency is not too unlike a very thick-walled McDonald's drink straw. I also got the end strainer which has a one-way valve in it. The one-way valve allows fuel to be sucked out of the tank, but keeps it from flowing back into the tank.

Step 1. I measured the distance from the top deck of the tank to the bottom of the tank. It is 11.5 inches.

Step 2. I cut the tube to create a combined elbow-tube-end-strainer unit that was 11 inches long as measured from the bottom of the grommet's deck flange to the bottom of the end strainer.

Step 3. I attached a new length of fuel hose to the elbow (using a hose clamp) and ran it over the fuel tank and down under the Deutz engine to a point where it would connect to my lift pump.

Step 4. I then pulled the grommet down off the elbow and onto the thinner metal tube. This is necessary for grommet installation. It gives room for the grommet to deform and fit into the top of the fuel tank. I also put a small amount of grease on the outer edge of its lower flange to make installation of the grommet easier.

Step 5. With one hand (because that's all you can get into the space, I pushed down on the grommet to seat it in the hole in the top of the fuel tank. With a very long screw driver in my other hand, I was able to squeeze the lower edge flange of the grommet inward so that it popped into the hole.

Step 6. I then pushed down on the metal elbow to get the larger diameter portion of the elbow to slide into the grommet and seal. Doing it in this order is necessary as you will never get the grommet to go into the hole if it is being held out to its maximum dimension by the thick part of the metal elbow.

With everything installed, the base of the fuel strainer should sit one half inch off the bottom of the fuel tank. If and when the tube ever breaks again, I won't suck air until the fuel level in the tank is about half way down due to the metal extension. Once you have everything installed, you'll have to connect your new fuel hose to the priming bulb and then prime everything before attempting to start the engine.

...and that's how you fix the a broken internal tank fuel suction tube on an 863 Bobcat.

 

[huckleberry]

had to replace my fuel line this spring on my 863. wished I thought about that ext. But I still had problems @ about 1/2 tank. after a bunch of diagnosing, I removed the fuel pick up line & found the line that I bought from the dealer was loose @ the elbow. I called the dealer & they said that they sell a spring clamp, but never use them because they don't need them. Anyway's I bought the clamp & installed it & haven't had any problems yet.

 

[Yellowdog]

Excellent, detailed repair response that will surely help someone in the future. Thank you!

 

[Defender]

In a related event in April 2022, I noticed my Bobcat 863 starving for fuel when under a big load and going up hill. I looked into it and found that the fuel priming bulb was being sucked in as if the fuel pump were trying its best to get fuel from the fuel tank, but something was blocking it. I suspected the fuel strainer or the one-way ball valve at the end of the fuel hose down in the tank. Remembering what an awful job it was to get to that, I dreaded tearing into the machine to inspect it, but did so anyway. Jack up the machine, remove right rear tire, remove the side access plate, stand on my head and reach back into the dark abyss to feel for the fuel hose grommet that has to be removed before the fuel strainer can be pulled out for inspection.

Well, after doing all of the above, I determined that the fuel strainer and ball had been plugged up to the point that only a small amount of fuel was making it through to the pump. So I bought a new strainer/ball valve assembly for about $10 on eBay, and proceeded with the replacement-- but I realized that Bobcat had simply come up with a very STUPID design that would just plug up in the future, so it was time for a redesign to make it the way it should have been.

I purchased an in-line fuel filter and a one-way fuel valve that would be placed back in the engine compartment where I could get at them, inspect them easily, and replace them easily as needed. The fuel hose down into the tank would simply be an open ended hose. One advantage would be that were it to get plugged up, I could blow air back through the hose into the tank and unplug it-- something that could NOT be done with the one-way ball valve at the end of that hose in the Bobcat design. The filter I placed in-line is a larger surface area one that has a glass section allowing inspection of the filter itself. I have attached pictures of this improved design.

I don't know if Bobcat has fixed their STUPID design in more modern machines, but maybe they'll read this and figure it out. I hope never to have to reach back into this part of my machine again! My arm needs 2 or 3 more joints and a third eyeball to do that job effectively, but my arm is a GOOD design already and doesn't need modification.

 

[Tripowerpaving]

There is a filter in the tank with check valve on it some time algae if there is black slime on it may just shorten I found a leaf and and earth worm on mine wrapped around probably vandalism of employe I’ve seen them plug up then set and release the dirt and run fine there is plug in bottom you can drain atleast 873 g I can I put new line and filter recent I got alot water in system and need to drain one side is chain case I think left is side is fuel tank there is usually a 2 bolts and a plate it will Be about arms length in on bottom draining it out gets algae and water recommend low tank when you do it have some good clean catch pans ready to swap because it’s alot of fuel fast

 

[Defender]

Question: In the second photo just above (the one showing the dirty top of the fuel tank) there are three hoses. One is identified as the hose that ultimately provides fuel to the fuel pump-- but where do the other two go? I assume the thicker one is probably the tank fill-hose. Is the other one a vent?

 

[ozarkag]

Thicker one is vent, other small hose is fuel return.

 

[Defender]

Follow-up Question: Is the vent hose open to the atmosphere, or is there some kind of check valve that keeps dirt and insects from getting into the diesel fuel tank? Wouldn't a vented fuel-tank cap serve the same purpose?

 

[IceHole]

Wow that machine is CLEAN for being an older unit.

 

[ozarkag]

Tees into filler neck hose, below vented cap. Vent is is to allow air to escape tank while filling.