05 nissan frontier,4.0,standard shift,smell gas, get spark,no codes.cranks but will not run. tried crank sensor and ran for about 15 min.,and back to square one.any idea?

Based on your description, it sounds like there could be a few possible causes for your crank, no start issue.
First, it's possible that there is an issue with the ignition system. Since you mentioned that you're not getting any fire, this could be a sign that there's a problem with the ignition coil, spark plugs, or wiring that connects the ignition components.
Another possibility is that there's an issue with the fuel system. You mentioned that you've already replaced the fuel filter and pump, but it's possible that there's still a problem with the fuel injectors or the fuel pressure regulator.
It's also worth checking the battery and starter to make sure that they're functioning properly. If the battery is weak or the starter is failing, it could cause the engine to crank but not start.
Finally, it's possible that there's an issue with the engine itself, such as a blown head gasket or a problem with the timing chain.
To troubleshoot the issue further, you may want to consider taking your vehicle to a mechanic or an auto parts store that offers diagnostic services. They can use specialized equipment to help pinpoint the exact cause of the problem.

did you reprogram the New ECU to the Truck ? if not there is your Problem , if crank or cam sensors fail to operate ? this truck will not crank at all , the Distributor in this year Model truck is old school mechanical type and they are the safest in market . they have internal mechanical driven pulse ignition modules if these modules fail ? you will have crank but no spark without ground short . you must Have either unprogrammed ECU ? or a wiring short in main Harness ( between power and ground ) to cause ECU to fry , Ignition non these trucks are also direct power supply with 40 Amp .
do you have the complete service Manual for it ? if not here is a gift for you : 1999 Nisan Frontier, KA 24 class
http://pdf.textfiles.com/manuals/AUTOMOBILE/NISSAN/frontier/1999-KA/ec.pdf

As new as your Mule is, it'd have a computer to actuate stuff. Hence, check the water temperature sending unit, it may be staying in cold start mode because the sending unit/sensor, is not sending the "I'm warmed up" message to the computer and it's just flooding itself with gas if that sensor is bad. Just a thought friend.

Please understand the fault code you have, it doesn't mean the sensor is defective, many other factors cause this code. Go to the link please. P0340 Nissan Camshaft Position Sensor Circuit Bank 1

If you have replaced the crank sensor and the code comes back, it may be a problem with the wiring harness or connector, or the plate the sensor reads.

My vehicle would alternate between running normal and missing very badly. I changed plugs/wires, now it runs great.

Take one of the spark plugs out and let us know what it looks like. Dry and light grayish tan means you have spark but fuel supply problems. Wet spark plug that smells like gas means it is more of a spark issue.

Good Luck

P0340....Camshaft Position Sensor 'A' Circuit (Bank 1 or Single Sensor)
P0325....Knock Sensor 1 Circuit (Bank 1 or Single Sensor)if you have no spark it your cam sensor

please.. 1991 chevy lumina..mech has car for 4 days..
repl ICM.ECM..checked ..all fuses.cranks..no run..smell fuel.
says spark good.Fuel press @ 42. put light on fuel injec sensor
..tells me weak signal( light shud be brighter) .Says it ran once
in 4 days for 2 min & died..." tells me injectors not accepting fuel