I changed the crankshaft position sensor twice and the van still doesnt run right and the computer still says is the crankshaft position sensor

You are either not getting fuel or the crankshaft position sensor has failed. on some mercedes the fuel pump will not run if the computer does not see rpm. so the easiest and cheapest attempt to repair is replacing the crankshaft position sensor. it is located at the back of the engine near the transmission bell housing.

ITS LOCATED NEXT TO THE CRANKSHAFT PULLEY . ITS A SIMPLE MATTER OF TAKING OUT THE OLD AND PUTTING IN THE NEW.

P1345 is "Crankshaft position sensor / Camshaft position sensor correlation"

Code P1345 determines if the distributor is installed incorrectly, or if a mechanical malfunction is present in the engine. The light will trigger when the engine is running and the camshaft sensor reference pulse is not detected at a correct relative position with the crankshaft pulse. Most likely causes for this Chevy check engine light code include a faulty crankshaft position sensor, a wiring concern or an improperly installed distributor. A quick check on the crankshaft sensor is to monitor the RPM value with a scan tool while revving up the engine. If the reading is close to twice the expected RPM, then the sensor is likely faulty. There are other less likely concerns possible, such as base engine or computer related issues, but these involve more in depth testing. I hope this information is useful.

On the 4.7L, the cam position sensor is located on the right cylinder head (thats the passenger side) toward the front below the valve cover gasket. Not on the front of the head but on the side where the exhaust manifold is attched at the forward end of the head. The crankshaft position sensor is located on the same side (right) but is at the opposite end of the engine between the bell housing and the block. The crankshaft position sensor can be replaced without removing the engine or transmission, it just looks tight. Also, on the crankshaft position sensor, it slides out of a rubber gromet. Here's a few pics to help.

Your talking about an astro van right? If so the timing is not adjustable. It is set by the computer, using various sensors, like the crankshaft position sensor, the throttle position sensor and others.

Check for a crankshaft position sensor circuit being open, or the crankshaft position sensor is bad.

Try to spray starting fluid into the intake of the engine, and then if it starts for a few seconds, then it's a bad fuel delivery problem like a fuel pump or clogged fuel filter.

If the glow plugs aren't working then the Diesel won't fire up.

How old is the Diesel in the truck? Is it out of season?

Crankshaft Position (CP) Sensor OPERATION The CP sensor is mounted on the right front of some V8 engines, is a variable reluctance sensor triggered by a trigger pulse wheel (36 minus 1 tooth). Its purpose is to provide the PCM with an accurate ignition timing reference (when the piston reaches 10 degrees BTDC) and injector operation information (twice each crankshaft revolution). The crankshaft vibration damper is fitted with a 4 lobe pulse ring. As the crankshaft rotates, the pulse ring lobes interrupt the magnetic field at the tip of the CP sensor.
TESTING -crankshaft position sensor Using DVOM on the AC scale and set to monitor less than 5V, measure voltage between the sensor Cylinder Identification (CID) terminal and ground. The sensor is okay if the voltage reading varies more than 0.1V AC with the engine running at varying RPM.

you dont specify what make,the crank sensor sends refrence to the cam,coil before they will work they need pulse

That sounds like a problem with a cam or crankshaft position sensor, and there might be a damaged sensor or tone ring, or dis-connected wiring to the sensors, or there might even be a camshaft out of alignment.

The crankshaft position sensor is located on the transmission bell housing on the right side (if you're facing the engine from the transmission side). The camshaft position sensor is towards the top center of the timing cover on the front of the motor. They both have 3 wire connectors that are virtually identical.

I had a the same problem with my 95' Silhouette it got worse and then would not restart until it cooled off. the problem is most likely the crankshaft position sensor this is what resolved my issue.