OK, I bought a 99 jeep grand Cherokee 4.7 4wd, changed out the timing chain, camshaft position sensor and crank position sensor, it still won't run, it's firing, you can smell fuel, it spits and kinda backfires out of the throttle body, the timing is spot on, no way to get it wrong... I'm completely stumped, I changed the gears the guides, the tensioners and the chains, I spray starting fluid in the throttle body and still won't fire up, if anyone has any knowledge of what I'm dealing with I would be more than grateful for your input, please and thank you!!