After a couple years of looking, I found a Wacker RTSC3 roller that fit the budget/condition, 390 hours and tight. It has the Kubota engine, not the Kohler/Lombardini. Runs like a champ, but under about 40° or 45° it struggles to fire. Glow plug voltage/resistance/continuity is good, fuel/air filters new. The manual says that the glow plug cycle is only 5 seconds for the Kubota, 30 for the Kohler. Other Kubota engines I've had, including presently the one in my Bobcat A300, run about 10-20 second cycles on cold starts. They have all been very reliable starters in cold weather. The Kohler powered rollers I've rented have also been good; I was after a Kubota powered one specifically for that engine..they're pretty bulletproof. Is there any way to program the thing for a longer glow cycle?
I know it's been a minute since you posted, but just spotted this. As far as I know there's no way to adjust the settings in the ECU (Wacker side of things is the little 2 button tool, pretty sure the Kubota side is too old school to plug into). How many hours are on the machine? Have you checked/adjusted valve lash? Glow plug spec is 0.9ohms.
I have not checked lash, 390 hours on the machine. Ohms check out and I physically removed the plugs and checked that they heated up. They did, but nowhere near what they should be for a cold start..5 seconds is not enough for the resistance to build anything like warm, let alone hot. Tried running multiple cycles, it takes 6 or 8 at 40° or so to even get a rough fire pattern going; plugs cool enough between cycles that it's kind of pointless. I contacted a Wacker dealer over in Billings, he said it was probably possible to manually wire in a circuit to shut the plugs on/off, but whether it'd mesh with the parent ECM is questionable. The Duetz diesel in my Bobcat 442 also runs a rapid glow cycle, but it's more proportional to the ambient temp. I've only had that machine for a year now, but have not found it anything other than reliable to start in cold weather. Had a couple cold starts in 20° or so, it ran a 10 second plug cycle and fired right up. Everything else I've got runs a minimum of 10 seconds, and my L8000's 8.3 Cummins runs about 30 seconds depending on temp.
Dumb question but have you checked the glow plugs? We have the same roller with Kohler engine that didn't want to start when it was cold and I'm in the South where it doesn't get cold. Replaced the glow plugs and she'll fire right off.
Kubota doesn't even recommend checking valve lash until 800hrs, so probably fine. One of the first things I was thinking was to wire in a manual push button for the GPs, but you'd need to remove the wire currently feeding the GP rail so you don't back feed the ECU. It would be a quick and solid fix. Only other thing I'd be checking is if you're getting full voltage for even those 5 seconds, or if you're getting too much voltage drop from the battery or a GP relay not holding.
Yeah, I've been down the obvious list with a multimeter and test light, checked voltage/resistance and physically checked that the plugs are all heating up. They do, just not enough time to get more than barely lukewarm, which in cooler temps doesn't cut it. I'm a little curious why the Kohler gets 30 seconds and the Kubota only 5..that's weird. Gonna take the above advice tho and check valve lash; if the thing ran crappy otherwise I'd be nervous, but it's a sewing machine after it's been started once, even if it's sat all day after a brief run in the morning.
One thing I didn't do was check the voltage straight off the battery..everything works fine and the portable set recharges in good order so I assumed the main battery was solid. I do have correct voltage/resistance in the line and through the plug harness, so I assume it's okay. There is a pretty good schematic in the owners manual, far as I can tell things are in spec, light array in the operator's feedback array is correct. The thing won't turn over unless the pre-startup procedure is done and I'm seeing yellow. I'd love to wire a hard switch into the plugs, but I've got a feeling that's somehow going to make the ECM hate life..it needs the feedback from all systems to be okay with turning the engine over. I will also isolate and check the relay, make sure it's good, but since I'm getting correct voltage to the plugs for the 5 seconds I think it's good. If I could figure a way to override the ECM and electrify those plugs for 20 or more seconds, I'd bet a day's pay she'd fire without a hitch.