While operation under load, the rpms and power drops down without stopping, then regain power only after a short while loses power again
Welcome to HEF BERT1. :drinkup Just to confirm, you're saying the engine rpm drops when this happens, and it recovers after you let off of the load? If so, most likely a fuel supply/restriction problem. Have you first changed the fuel filter?
We havE REPLACED THE FILTER AND FLUSHED OUT THE FUEL TANK AND FORCED AIR THROUGH THE FUEL LINES AND HEARD BUBBLING FROM THE TANK. WILL BE REPLACING THE FILTER AGAIN
I hope the ALL CAPS is a typo, I'm only trying to help. :beatsme One thing I can tell you, forcing air through the fuel supply lines on a Bobcat is a bad idea. Many Bobcat machines, and most likely include the 853, used a strainer on the end of the pickup tube in the tank that has a ball check in the stainer, meaning, if you blow compressed air in the fuel supply line in an attempt to clear any blockage you'll blow the fuel pickup tube clean off inside the tank. Aside from that, I'll wait for others to chime in for advice.
^^^ this. for starters you probably blew the screen/check valve off the suction hose in the tank. sounds like you may have a suction side leak in the fuel system. :drinkup
Probably a crack in the ful hose. Happened to me on a job far from home on a weekend when I had very limited time to get the job done. I ended up "borrowing" the winshiled washer hose off my truck to replace the fuel pickup hose inside the fuel tank.
Our next procedure is crawl down in the cab, remove the pickup tube and check it out. Thanks, will let you know the results
if this is the same issue I am having on my 863. where is the pickup tube located? can I get to it from the side of the tank by the filler tube? I don't think I blew the ball off because when I was blowing air in it, it would build up pressure and I would hear the ball clicking sorta. then release air and do it again. but when I suck on fuel line it wont pickup any fuel.
You'll have to pop up the can and you'll find the pickup tube/hose running through a grommet in the top of the fuel tank. It's down low back by the engine.
I stopped to get a few parts so I can at least get it in garage. Thanks guys.
The last time we pulled the pickup tube, we crawled into the cab on top of the hydralic lines really tough reaching under everything to above the tank. What did you mean "pop up the can"? Bert
I think that was cell phone doing the spelling for him
Cab. Lol
Had the same problem, if you blow ari Into the feed tub and don't get air coming back through the tub, the line and the Check valve is working. I did the same thing and air came back through the line. When I took out the feed and return line they where both gone. All I did is pressurize the tank, i did replace them with some fuel line I had, temporarily, was thinking of switching the pickup tube to a solid stainless steel line. has anyone done that before? don't know if that would be a good idea when we are working on even ground..
theres a check valve there for a reason..... bobcat has been using the same fuel pickup system since 1980.... why try reinvent the wheel? :drinkup
finally was able to get machine started and in garage where I can work on it. still stumbles then revs back up to speed. I tried to locate the pickup tube but just cant seem to locate it. then I removed the fuel bulb and it seems to have fuel flowing steady. could my stumbling be another issue? I have replaced the filters, pump, and cutoff solenoid. Also can you better tell me if the pickup tube is maybe near the center of tank? that is where the line from the ump goes under the center of engine.
theres at least 1 other 863 fuel problem threads currently active right now, might try browsing through it, i'm pretty sure you'll find some answers there. but to reiterate, sounds like you may have either a cracked or broken fuel suction hose in the tank suction leak pinched fuel hose from the tank to the primer bulb, or bad primer bulb :drinkup
thanks for info. ill see what I come up with today when I get out to garage.