MY JEEP WILL START BUT TURNS OFF AFTER 4 SEC - 2000 Jeep Grand Cherokee

every car comes with 2 keys --use the spare key

did you change the gas in the tank? it could be that the gas is old so it won't light so it won't start

which engine of the many, ??????
no start but cranks ROBUSTLY right?
turns over means zero, the starter motor and engine both can TURN OVER thus , no meaning, What counts is the crank shaft spins.
called Cranking.

1: check all fuses on both boxes.
2: Is dash I/P cluster CEL lamp glowing keyon?
3: I then connect my scan tool and crank for 5 seconds, not 4 , but 5.
3A: got DTC's (errror) for CMP , CKP or spark or dead RPM?
thats 4 checks,, got them, ? yes, BINGO.
the ECU will not INJECT fuel of those are bad. ever.
there are exceptions, but those guys get lawsuits....
4: above is ok , i check spark (some do this first. sure thats makes sense , always)
5: ok I got spark on all cylinder, NO , fix that or do step 3 again.
6: i try test fuel, I spray it in and BAM it runs for 3sec, and dies.
if it dont run, are those 100k miles spark plugs long dead???? ever do tuneups, ever?
if runs 3 sec, and sound great. then you lost fueling.
i check for flooding only if spark is good.
if you get here, the story can go long play, as fueling is complex.
( no injections, leaking , clogged, ECU inputs all wrong, fuel pump dead or weak, FPreg fubar. long..... ask.)

It is not getting gas. Could be bad fuel pump,and most are now in the fuel tank.If it is the fuel pump and it is in the tank,this can be a fairly major expense.($400-$500)This is not an unusual problem,and many auto repair shops can do it.

If it will crank but won't idle then it is the idle air control valve

Check fuel pressure, check timing and check plugs and cap & rotor

sounds like tps sensor mine did that if you push on gas pedal will start

Check fuel pump for pressure and output. If it's not that, don't start guessing... have a scanner put on it and get some codes. While some codes can be ambiguous, it will serve to start you in the right direction!

I am going to assume that you didn't accidentally put DIESEL in?? If you did, siphon all you can out and add fresh GAS(!) and 3-4 bottles Octane booster.

Squirt a bit of Starting Ether in the Air CLeaner inlet
Start Jeep
Squirt Ether
Start Jeep
Start Jeep
Squirt Ether
Start Jeep
Repeat until it runs. Do not use alot of Ether - will blow engine!!!
Fixed!

If you didn't put Diesel in, and KNOWING that the problems are usually FIRE-related, replace all FIRE-related parts ($40.00)

Get new ROTOR (Thingy that spins inside CAP, distributes HVolts)
Get new CAP
Get new cables (change cables to new CAP 1 at a time!!!) DO NOT RUN cables neatly. Cross them over each other in looms
Get New sparkplugs (Do not overtighten. Turn to seat snugly, then 1/4 turn more

on most remote start application a wire is installed in motor with one wire on the fuel injectors that wire reads rpm if its to high it stalls if to low stall so check wire get back to me