My dads 1996 dodge carvan sometimes doesnt start but the its not the battery, what can it be?

Sounds like the alternator is not charging the batter enough , But first clean the battery terminals and see if that helps,

Could be a fuel issue, or an electrical issue, hard to tell without getting into more detail, have it checked by a mechanic

Its a Chrysler product.Same for any mexican chinese parts american car.

Does it make any noises? Does it click rapidly? Click once? Clunk clunk clunk? Starter, ignition solenoid maybe? Need more details. When you get the car started, get a multimeter and set it to volts and put it on the battery, you know how to do this anyone can, if its reading 14v-15v your alternator is fine, check your battery afterwards, leave the car running for about 15 min. Do this to the battery with it off. If its 12.6 or very close to it your battery is fine, anything below your battery is at half charge and get a new one.

you do not give information about side of the engine, i.m guessing is not a 3.0 liter, usually the problem is the cam or crank sensors

you can play games and ask what, but in the long run ,take it down and let them put a tester on the motor, and it will tell you whats wrong in a few mins.. save time and cash!!!

Ok......So you say it will run fine and then when you shut it off.When you try to start it again, will crank and crank and crank, but will not start up. Probably a fuel pump issue. Most probably the fuel filter is plugged and the pump is overheating, common with Dodge. Or the pump is past the stage of overheating and needs replacing.

this people don't know nothing about electrical systems, when you say it won't start, is the engine cranking? if it doesn't crank then check you starter relay, you can just swap it with the horn relay, if it still won't crank replace the starter motor. if it cranks but won't start, may be crank sensor, cam sensor, fuel pump or pcm. all this are common problems.