You state that your receiver is 5" away from the ignition module.You need to have at leat 12" between any radio
equipment and the ignition module.Also you will need to do a thorough range check to make sure there is no interference.
What radio system are you using? I am using a Futaba 9CAP 72 mhz in my GP Extra 300 with a DL-50 gas engine without
any interference problems.I set up my plane systems by using this as a refernce to go by from Futaba.I range checked my plane
with this method and have not had any problems.

Hope this will help.
http://www.futabarc.com/faq/faq-q331.html