Howdy all - Heavy heart as I type this. I have an old 843 that has been my workhorse. When she started bogging down (again) I was pretty sure that the cheap parts and fuel lines I didn't replace last time were coming back to haunt me. So, I started replacing them. I don't get to spend much time working on the property, and this has gone on a few minutes at a time over what I'm ashamed to admit are many months. The Amazon pickup tube in the fuel tank was first (junk hose), replaced with a full new pickup kit from the local Bobcat dealer this time. Then when that didn't fix it, all of the hoses (and they looked like they needed it, but still didn't fix the problem). I had replaced the fuel filter (old style, with the glass bowl) early, so I decided that the problem had to be there. It wasn't. FINALLY, I've got all day Labor Day to knock this thing out. So, for the last round, I did what I've read about countless times and never done before, and put a piece of clear hose at the end, right before the injector pump. And there were bubbles. The second new fuel bulb from amazon leaked as bad as the first. Dealer wasn't open, but I bought the twenty dollar one from Cabela's. That took care of the visible problem, one tiny bubble over about 20 minutes. Good, clear fuel in the hose. BUT... She's still bogging down, maybe a third to a half of throttle is where pushing the lever stops making a difference, pretty much the same as it's been this whole time. And, when I opened the bleed screw on top of the injector pump, a whole lot of air was coming out. I could pump the bulb, the bleed would mostly clear of air, then tighten the screw, but after several seconds, she'd bog down again, and I'd get lots more air when I'd open the bleed screw again. I sprayed starter fluid all around the pump in sections, thinking that it might get sucked in somewhere and rev a bit, but she never reacted. The only thing I know about those pumps is that they are expensive. I thought about installing an electric pump, but I'm not sure enough of how the injector pump works to know if that would help. I'd appreciate thoughts from you guys who know this stuff, I've no experience here other than what I've related. Am I missing anything, or do I have to replace the pump? Thanks much - dave
Take the air cleaner out and don’t put the cover on.. now run it & see how it acts.
Both filters need replaced,that's sure. It's a little stronger for those first few seconds, then drops back. A little more erratic, lower lows, but brings itself back to what I'd say is "half stick" speed, doesn't change when I bring the stick more forward. I opened up the bleeder again, lots of air, got it mostly gone and shut the screw, then maybe 30 seconds and repeat, with lots more air.
Before I saw that reply, I got to wondering, if it's pulling in that much air, shouldn't I be able to make it spray or even leak from the spot, using the primer bulb? Tried it, and I couldn't see or feel spray, or notice drips.
Does it have a supply pump.!! Have u tried back blowing the line from the tank.?? BE SURE to remove the cap first and listen for bubbles. There’s nothing wrong adding an electric supply pump, just make sure you’re under 10 psi..
It does not have a supply pump that I have found, the line from the filter runs to what appears to be a "Zexel" pump (as best as I can match from pictures), it looks to me like it's a single piece unit with the supply coming in the back of the unit and the pressured fuel going out to the injectors via pipes on the other end. I have tried blowing back through the lines, with little success, but the clear tubing just before the pump intake I THINK rules out any other source of air. I suppose it would be possible that one of the new hoses could be collapsing inside, but it would have to have been both the old and the new. I am really interested in the electric pump option, as it seems cheap and easy. But would it provide enough push to keep the lines filled at any throttle position and stop the air intake? And of course, which one? I'm loathe to buy anymore cheap chinese stuff, unless you or someone else knows of a good brand (cheap or otherwise, those injector pumps are crazy!). Thanks for your thoughts so far!
Provide enough push.?? You’re running off of gravity feed now.. so anything above that would be sufficient.. BUT.. stay under or at 10 psi..
Okay. The reason I questioned it shows my ignorance. I know it's gravity feed, but as it is drawing air in along with the fuel, I assumed that at high throttle the pump was actually drawing fuel at a higher rate than gravity through the 1/4" connections would allow. I stand corrected. I've been looking at actual Bobcat brand electric pumps from the newer models (I'd like to stay away from the chinese stuff). They only seem to have a couple that they actually use, but I don't find any specs, including PSI, hose size, or even the electrical connector type (I can work with the last two, it would just be nice to know). Am I safe to assume that flow rates should be similar from old to newer similar sized models? The one I'm looking at specifically is 6684852 .
If it were mine, I wouldn’t spend but 20.00 on a thought that it “might” fix my problem.. Chinese throw aways are fine to diagnose your problem.
Fair point. Thank you.