91 Dodge Ram Van 350 not starting

I think you need to have the BCM inspected or replaced if POSSIBLE .also,thoroughly inspect all wire connections, particularly in the regions where the mechanic had been handling the auxiliary battery.There could be a loose connection or any daamged wire

have you checked the ignition switch thats on the steering column shaft, when you turn the key it moves a rod that moves positions on the switch.

Go to your computer search for fusebox diagrams and find out where the starter relay is, most likely its a square black box inside the under hood black square fuse block.

Check the neutral safety switch on the transmission. It should have three wires on the connector (if I remember correctly). There should be power on the Brown with yellow wire with the key in the crank position. If there is ground that wire and see if the van starts. If it does replace the switch. If it does not check the starter relay. Let me know if you have any questions and I'll do my best to answer them. Thank you for using FixYa.com!

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

There could be a bad battery connection or possibly even a bad ignition switch causing momentary loss of power to the Central Timing Module or the

your crankshaft position sensor or its connector is bad

you pinched a wire into the bellhousing between the tranny and block!!! it! happens

WCM lockup possible pull the IOD fuse it is a double 30 amp fuse pull up on it and leave it out try to start it then the will reset the computer. The WCM is the computer for the key and anti thieft features. hope this helps please rate if it does.

Check the relays

Do you have the model with circuit breakers below glove box? They reset themselves when key turned off, but if still a short, or excess draw they will trip again. After while they get pretty weak and may trip constantly.