might be the fuel pump. crawl under the truck and beat on the gas tank and get some one to try to crank it. if it fires your fuel pump was the problem.
If you mean it won't crank then the starter is defective. If you mean it will crank but not start it isn't getting fuel, spark or compression.
Its the solenoid (relay) that you are jumping. If i understand you correctly, it cranks when you cross the relay. Just ask for starter solenoid, and stick in on like the old one.
Usually when a starter solenoid/relay switch is bad, you will hear only a click and the starter will not spin (crank).
Dodge Dakota V6's didn't have a crank sensor until 1992.
might be starter relay, or the crank circuitry from the switch or to the starter from the relay. I would trace back from the starter to the starter relay back through the neutral safety switch to the ignition switch.
your battery is dead or the starter solenoid
When you say 'crank over' are you saying the engine won't do anything? First check your battery and then your starter or starter solenoid. You can turn the crank to check if the block is seized or not.
Or a crank
the starter
When does it click and does it Crank when it is clicking
The crank sensor is behind the starter. Remover the starter at the back of the engine and you will see the sensor
No Crank Sensor until 1992