two nitro rc cars wont start?

i got 2 used nitro rc cars the other day and they both wont start. im doing everything right. i have a HPI RTR rs4 3+ evo and a HPI RTR rs4 drift car. the guy said he had them running a day ago but they wont run for me. Ive sat outside pulling them 5mins at a time. i really need some help! i wanna drive them!

They are a pain in the ass. Try shooting some wd-40 down into the carb, and pulling the starter to shoot out any gunk. That won't garuntee a start but it makes it easier. More importantly make sure the glowplug isn't covered in gas. Other than that, all i know is to keep cranking till it turns over. Sometimes they need lots of motivation