Douglas,

Use a bigger battery for the ignition. Better still, if you use a 2.4 radio, use dual batteries and draw power from the receiver. That balances everything out and this works well for many people. I have three of these engines are they all start flawlessly. Your problem is most likely a low battery.

About the fuel being sucked in, just use an "injection syringe" (I use the one from JETT : the bubble JETT fuel tanker; this is actually used to fuel bubbleless tanks but works great for the 170 CDI 'starting problem') to force the air into the fuel tank vent. This pressurizes the fuel and you can then see the fuel go all the way up the piple into the injector. As soon as this happens, stop the 'air injection' and start the engine. Starts every single time.

Atul