My trooper cranks over when started but the engine

which engine, ill toss coin, land on v6
check fuses first.
wont crank? that grrrrr grrrrr grrrrr sound
jumper cable start it yet, why not?
or put in a known good charged car battery?
or using any battery charger charge yours?
or buy a new battery, (if rich)

if it cranks and wont start?
check spark x6 (scan it yet?)
if sparks ok try test fuel!
if test fuel fails 100% see bad belt below.

EVER REPLACE THE CAM BELT?
if not and over 60k on the last one
the belt is doomed, living on borrowed time.
got the V6?

check for spark
if spark is good and will not run on test fuel
check cylinder compression

If your Trooper "cranks" but doesn't start or runs for a few seconds and stalls out, your fuel pump has gone bad. They are notorious for this. If you replace your fuel pump, replace your fuel filter. More information is needed though.

Is the 30 ltr engine diesel? If so what was the reason and changed the Injectors? Did you follow the correct procedure to renew the injectors? This engine has two oil pumps. One is for the engine and the second one is the high pressure for the injection cranking system. On starting the engine and trying to start are you sure you receive the correct oil pressure to cause the injectors to open? If everything is okey,go to crank or cam sensor or even to the accelerator pedal.Also is better to clean the throttle body from any dirt. Use a scanner to give you the fault .Also bear in mind that these vehicles are fitted with the following secret,if you have a blown brake lights fuse or brake lights bulbs will not start,just engine turn and no engine run. It is the immobilizer activation. Do not over 32 times crank start otherwise you will loose ecu.

Great.

CHECK FOR FUEL SOUND LIKE FUEL PUMP FAILED.BUT CHECK FUEL PUMP FUSE AND RELAY.

First, blow the fuel pipe with a strong air jet & change the filter. If this didn't work, change the main fuel pump (do NOT repair).

fuel pump bad

check your fuel delivery from the pump to the "dry" pulsing injectors leave the crank sensor alone! open the intake and, spray either (engine start) into the engine then attempt to start; it should start and, run until the either is used up then die. most likely your fuel filters are clogged

have someone kick at the gas tank while you are turning key if it starts it is fuel pump