Two coils, with one hardwired spark plug wire on each. It's actually a pretty nice and simple setup, but I'm willing to bet those coils are $100-$200/each, meaning another few hundred dollars at a guess. Not the end of the world, but I'm already into this motor for more than $1000, and no closer to "fixed". I should have mentioned yesterday, that there's still a lot of positive pressure up at the oil filler cap on the valve cover, and even some positive pressure at the dipstick hole into the lower crank case. I'm not sure what's normal for these machines, but the tech manual suggest I should be seeing up to 4 inches WC of negative pressure at the dipstick. I mention that, because the fuel pump is an impulse pump, driven off of what I assume should be a vacuum line on the valve cover. The only test for the fuel pump is cold cranking, no way to test it with the engine actually running. But if it's seeing positive pressure when it should be getting vacuum, I could be having a fuel delivery problem, nothing to do with ignition. Rigging up a temporary gravity-feed fuel cell would give us an answer on that, I suppose, but easier said than done. Anyone got a spare IV bag?
Have any engines around with a tank that could easily be unbolted and hung for a test? The other thing that comes to mind if the coils are easy to get to /swap out, maybe buy a cheap one for a test coil, then OEM if they prove bad?
These are magneto coils gapped .012” off the flywheel, so while I do have quite a few automotive ignition coils laying around, only the OEM or specific aftermarket will fit. Time is a bigger problem than cost, to a degree. If it wasn’t half a day of work to access these coils and swap them, I’d just do that. I mention that, because if there’s some cheap fuel cell or drip bag I can just buy and rig up, I’d favor that over taking apart another machine! I’m literally thinking along the lines of colostomy bags or Camel Back water bags, if any are resistant to dissolving in gasoline and causing even greater problems.
I have a Mule (Kawi v-twin, similar design) and I have the exact same thing. Tons of air up the filler cap. I found it very alarming but assumed it is normal. If I can remember I'll go test my zero turn (Kawi v-twin) and see if it's the same.
Also im not sure why you are thinking of rigging up a gravity feed to test fueling issues (musta missed it), but I feel like this would be easy to rig up with a mason jar and some ace hardware hose barbs. EDIT: I went and fired up my zero turn and the air comes out the filler cap about the same as my mule. Buncha oil came with it too.
Right...I meant a cheap aftermarket knockoff coil...but if they are not easily accessable then probably not worth doing that. Those aftermarket nurse tanks work great, we each had one on a stand at the bike shop...using known good fuel/supply was always a good start when doing diagnostics...
The issue only acts up after some time, sometimes not for a few hours, other times after just 30 minutes. But I'm not going to bounce around my yard at 11 mph on a dual joystick machine, while trying to hold a mason jar full of fuel over my head. lol... Anyway, the portable 1L tank posted is perfect for this need. I'm assuming gravity feed will provide sufficient pressure, the fuel pump is probably only required because the OEM tank is below the carburetor. I'll also try to find time to get pricing on new coils. Yeah, they're a PITA to get at, you basically have to lift the engine at least part way out of the machine to get the blower housing off, just to get at them. It's at least a few hours of work to get in there, swap the coils, and then get everything buttoned back together.
I've been thinking more on this overnight, and I guess it must come down to whether an impulse pump really cares whether it's getting vacuum (relative to ambient) or if it operates just as well on any impulse, positive or negative. If I were the engineer designing such a pump, I'd design it to work off any impulse, lest the thing fail to pump whenever there's positive crank-case pressure. This, along with the intermittent nature of the behavior, has me suspecting ignition coils are the more likely culprit, but I'd like to hear from anyone who knows how these fuel pumps actually work.
Exactly as I suspected. And since I'm already meeting fuel delivery rate spec just cold-cranking, this would seem to rule out fuel delivery problems.
Great video, I learned something. Ever driven a car with bad coils? I had a E36 that would start and run perfectly fine and then as it got warmed up would start missing.
Yes. I had one car that had a bad coil that would just cut out randomly. Took me forever to diagnose that one. But even more to the point, I'm old enough to remember driving many cars with mechanical distributors. The slow stuttering up to speed is very reminiscent of a bad cap or rotor = weak spark. So, I went ahead and ordered two new ignition coils this morning. Only $83/ea thru Deere, so not even worth considering aftermarket.
Unless the issue is the supply line is collapsing internally, cutting off the pump's fuel supply. The inner lining of the hose deteriorates and turns into an indecisive check valve. When it decides to close, the suction from the pump just closes things off even tighter. That one can be a royal b**** to diagnose as it's rarely consistent in how it presents (however, coil failure is normally pretty consistent in response to load, heat, engine speed, etc.), looks/feels a lot like a fuel tank venting or ignition issue. If fuel delivery is the issue, there will be little to no fuel in the bowl of the carburetor when the engine is running poorly. Sometimes you can crack open the bowl drain screw and observe how much fuel runs out. Often enough however, it's not that simple to observe. You could setup a sealed clear container to observe fuel flow. A sealed container on the pressure-side of the pump works. It'll need a dip tube inside for the line that connects to the carburetor inlet. The level in the container/jar should not drop while the engine is under load, but it will rise somewhat as the container pressurizes. Or you can just replace the $10 worth of line...
[QUOTE="MasterMech, post: 1562909, member: 4] Or you can just replace the $10 worth of line...[/QUOTE] That's usually my first action before I start pulling my hair out.
Thanks, MM! I had that line fished out of the tank last weekend, and it looks/feels good, but it couldn't hurt to replace it. I'll have to see if I have anything unreinforced and as flexible as the original, or hit Deere for the OEM part. In the meantime, the new coils came in this afternoon, so I'm ready to swap them if the fuel line doesn't resolve the issue. They're not super easy to get at, but I'm well-practiced in getting that engine pulled out and the blower housing off, at this point.
Oh, one other thing. I mixed synthetic and dino oil in this machine, just before it got really belligerent. It was leaking oil out the front main seal, see prior notes on positive crank-case pressure, and I had run out of the 10W-30 Deere Turf dino juice. So I topped it back off with Pennzoil full-synthetic. I can't imagine that has anything to do with the current troubles, but since it was an anomaly that occurred just before, I figured I'd mention it.
Maybe. But it was leaking before using any synthetic, on the OEM Deere 10W-30 Turf, dino formula. I only added synthetic because oil was low when I needed to mow, and it was the only thing I had on the shelf at the proper weight.
