We start regularly engines even up to 10 cyl Excursion engines. Just got a response back from a customer, 17 YEARS OLD that started her dad's 2000 Excursion when she was stranded....first time. Now, I don't know the details of your vehicle; if the engine actually starts reasonably well or is not well maintained and or needs repair in order to start or if you are starting it properly for a Super Cap Jump Starter.
You MUST, and I mean MUST start right when the counter goes to zero. Super easy. Hook the RescueMate to the battery, it will say "Read after a couple minutes", press the "Start Button" and start the vehicle in 5 seconds. Don not wait more that 5 seconds.. Our product is designed to start "reasonably well running vehicles" with the advantage of "not having to charge every few months". RescueMate lasts 10 years. Leave it in the trunk for 5 years and it will still work. Lithium doesn't even work below 0 Degrees unless you store the charger in your house (a lot of good that does you).