Burner won't fire

[mark17 14]

Hi guys. I have a landa mvp 3-3000 wlth 350hrs on it. The last couple off times I used it the burner didnt fire right away, it took a few sqweezes of the wand then it would fire up. yesterday it took 10 minutes of flowing water under pressure before it finally fired up. It seemed to burn well for the next 10 minutes but i noticed puffs of blue smoke now and then like it was going off and on. Today it would not fire so I need to start troubleshooting.

I dont know where to start, spark, fuel or air. And How do i check these thing without the engine running, 12 volt batter?

[bhenson 15]

Could be the trigger switch. The smoke could also be the burning off excess fuel being dumped into the burner during the time of it not working

[mark17 14]

Yah, thats what I thought the blue smoke was about too. Is the trigger switch the one coming off the pump that sences water flow?

[We Wash Concrete 64]

Yah, thats what I thought the blue smoke was about too. Is the trigger switch the one coming off the pump that sences water flow?

Yes. You can remove a couple of screws from this switch to reveal a small microswitch. You can control that microswitch manually to troubleshoot.

[Douglas Hicks 128]

The micro-switch turns on the burner, there may be a hi-limit switch that also turns the burner on. If one switch fails, no heat.

The micro-switch is operated when pressure from the pump pushes a small rod against the micro-switch. RREmove the cover adn operated the pw gun. If the rod moves, the switch may be the problem. You can remove the switch and use a multi-meter to test it or just replace the switch. The cost is minimal. If the new micro-switch does not fix the problem, I also change the hi-limit switch. That assumes you have a hi-limit switch. If the bore for the rod is too worn, you need to replace the whole switch assembly.