73 dodge van won't turn over

Refer to wiring diagram. It may help.
1996 Dodge Caravan Wiring Diagrams ' PDF ' Dodge ' Headlamp (scribd.com)

Your '89 has no OBD plug in. To retrieve codes, turn key on, off, on, off, on, off, and then leave on. (Cycle key 3 times on-off, then leave in ON, do not start engine.) Codes will begin to flash on the check engine light (cel). All codes are only 2 digits. Probably see a code 12-one long flash and two short flashes-code 12 is normal, disregard it. If you have to, keep repeating the codes until you get them all. Post them here, or google the codes for help.
here is a link: https://www.2carpros.com/articles/retrieve-trouble-codes-for-chrysler-dodge-plymouth-odb1-1995-and-earlier-car-mini-van-and-light-truckshttps://www.2carpros.com/articles/retrieve-trouble-codes-for-chrysler-dodge-plymouth-odb1-1995-and-earlier-car-mini-van-and-light-trucks

check the solenoid on the starter motor. Have the starter bench tested

And you know the fuel filter is good? Could be injector problem: just as a check, spray some starting fluid into the intake and see if engine runs a few seconds. If it does, it is a fuel problem. Check injector fuse, as a start. Check fuel pressure. Check injector circuit. If engine won't start with starting fluid, check if you are getting spark. Problem may be in the ignition system.

Pump or injectors may be bad .

If i understand you clearly. your van needs to be checked for mobiliser operation and/or key sensor ( Try spere key)(my email add: [email protected])

73 was an awful year for smog devices.
You could just look at any 1973 Dodge diagram, because a motorhome is no different.
But my advice is to take all smog stuff off. It did not work well in 73, and harms engine. You don't have to test anyway.

Use fuel line/injector cleaner this is a common problem. Also try higher octane gas for a tank or 2 and get her ou on the highway and blow he cobwebs outta he fuel system and exhaust

Try using higher octane fuel or octane boost in the winter this is a common problem on the dodge V-8s,after about 60,000 miles. However yours sounds like fuel line freeze up V-8s experience moisture in the fuel lines. Higher octane should help you may also wish to change your fuel filter, and run a fuel line cleaner through your van Seafoam is a good one.

key switch is bad most likely