Well now you know that it is able to run with the starting fluid sprayed into it. Your fuel from the vaporizer is suppose to be high pressure which it is to the injector holder. Your injector turns it into low pressure to feed the motor. If it was high pressure it would flood the engine and then it wouldn't start either. If it isn't supplying very much fuel through the injector holder then I would say that it is still clogged up with tar since you can't smell much propane. As I stated earlier sometimes even soaking the holder assy. will not breakup the tar inside. Solvents or brake cleaner usually will not break it up and get things unstuck. That sensor with the spring and plunger will actually boost fuel when the engine needs it when you step on the gas pedal. I tried something once, I fed propane from a propane torch into the air intake to see if it would start and run. If I remember it did start and ran but you have to feed it enough to get it started. ALWAYS BE CAREFUL WHEN WORKING WITH PROPANE!! Tar builds up inside a vaporizer and needs to be drained at times when the engine has been run and everything is hot. The tar turns into liquid form and can be drained. I'm wondering if you could pull the injector housing off and gut the sensors and injector out of it and dip it in boiling water for awhile and see if any tar softens to liquid and maybe it will get unplugged. I've never tried this ever before but it might be worth a shot. You have a lot of expensive parts already installed so it might work possibly. Hopefully it will start and run for you.