Hello to anyone with ideas....?

1991 Dodge Van 350 V8, 5.9l

Van starts but voltage drops and battery gets drained. I have to jump start or charge battery. Once it starts, it runs for a few hours but then has loss of electrical power and dies. Voltage meter on instrument panel registers, but drops when driven.

Just replaced Alternator, Starter. ECM was replaced about 2 years ago.

Any suggestions...?

Thank you kindly,
Shaun

Using a digital voltmeter, what is the exact voltage across the battery terminals when the engine is running?

How old is the battery?

I have a friend who has the same problem with her 1991. She went to Autozone and got her alternator checked out and it passed. She got a brand new battery before that, but no go. She still has to charge the battery everynight and along the drive on long trips. The mechanic told her it had something to do with a recall for the ECU and some module he had to add to it. I am not seeing any recalls online, but i will continue looking. I think it is something else, but hopefully someone can chime in and give a better solution.

She still has to charge the battery every night

Most likely the fusible link blew. Take a volt reading off the main output wire on the alternator to ground, with the engine running. What's the voltage?