Please let me know if you find a solution. I bought a B4L from Heatso this past summer, and am having the exact same issues. The heater seems to have a rough time starting, but works most of the time at my home altitude of 3k ft. At 6k, it might start after several attempts if I'm lucky. Over 7k, forget it.
Heatso has sent me a new fuel pump. No change. I've replaced all fuel lines and connections. No change. I've sourced the fuel line directly from a fuel canister to eliminate any issues with the tap/standpipe. No change.
Eventually I found the Repair Instructions Manual for M2/S2 heaters. This describes a fuel quantity measurement test. According to the manual, during initial startup, the pump should run for 105 seconds and put out 14.2ml of fuel. I'm getting barely 9ml and the pump runs for 115 secs. Once I told Heatso this, they said it was probably a faulty ECU. I sent my heater back to them. Supposedly they confirmed it was an ECU issue and replaced it. I just got my heater back (after 2 months). I ran the fuel measurement test again, and no change.
I really don't understand how they could have fixed my heater, when I'm still seeing the exact same faulty fuel measurement values as before. I haven't had a chance to retest at high altitude yet, but it's still only working marginally at lower altitudes, just like it always has.
Heatso has sent me a new fuel pump. No change. I've replaced all fuel lines and connections. No change. I've sourced the fuel line directly from a fuel canister to eliminate any issues with the tap/standpipe. No change.
Eventually I found the Repair Instructions Manual for M2/S2 heaters. This describes a fuel quantity measurement test. According to the manual, during initial startup, the pump should run for 105 seconds and put out 14.2ml of fuel. I'm getting barely 9ml and the pump runs for 115 secs. Once I told Heatso this, they said it was probably a faulty ECU. I sent my heater back to them. Supposedly they confirmed it was an ECU issue and replaced it. I just got my heater back (after 2 months). I ran the fuel measurement test again, and no change.
I really don't understand how they could have fixed my heater, when I'm still seeing the exact same faulty fuel measurement values as before. I haven't had a chance to retest at high altitude yet, but it's still only working marginally at lower altitudes, just like it always has.
