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Don't pull FP Relay, use "clear flooded engine" to test it
All fuel injection computers have the "Clear Flooded engine" routine, it turns OFF fuel injectors but leaves spark ON while cranking engine
Turn key on
Press gas pedal down to the floor all the way, and hold it down(at 0 RPMs and Wide Open Throttle, computer shuts of injector pulses to start "Clear Flooded Engine" routine)
Turn key to START
Engine should not start, it should not fire at all, no fuel, it will just crank
When you release gas pedal, even while cranking, computer will restart injectors
If engine fires and gets above 400rpms then computer will also restart injectors
Try it in the morning when you know engine would normally start, just to make sure it works, if you have a stretched throttle cable then computer won't see WOT(wide open throttle) so won't shut off injectors.
If engine fires in Clear Flooded engine then you could have a leaking injector OR leaking FPR(fuel pressure regulator)
But either of these should cause a noticeable drop in MPG
You have a Dual spark plug system, so you can test if all spark plugs and both coil packs are working, in a simple test
Unplug either coil pack's 3 wire plug
Start engine
Should run smoothly but slightly lower RPM
If it doesn't start then coil pack is most likely bad, but you can test that later
If it starts but there are misfires, rough idle, then some spark plugs on the coil pack are not working
Shut off engine and plug coil pack back in, and unplug the other one, restart
Either coil pack can run the engine just fine on its own, you get more power from an engine if there are two working spark plugs, thats the reason they are there, there is no other reason for it like you may have read, i.e. emissions, alternating spark, ect............it just gives engine better power, if you have room for a 2nd spark plug in the head
Dual plugs are great but you can't really tell if one spark has failed, because the other spark plug still works so no misfires, so you won't know there is a problem until BOTH spark plug in the same cylinder stop working
Clear Flooded Engine can be used for a few other tests.
I use it every morning to get oil pumped up thru the engine before starting, high mile engine
Also after oil change to make sure filter and passages are refilled with oil before starting