Wife came home from work, next day, van won't start, only clicks once. Battery is at 12.73, installed a new starter and solenoid assembly, starter relay checks out as do the three fuses. Battery terminals and connections to the solenoid have been cleaned. Battery cables seem solid also. Knowing new parts can be bad, I took the starter assembly down and bench tested it, and it was fine. am at my wits end. Any ideas?

 

Without the right equip there is one test you can still perform.
With the headlamps on, attempt to start the engine. Have someone watch the headlamps and see what they do as you attempt to start the vehicle.
What do the headlamps do?
Nothing,go dim, or go out completely. Depending on which result you get will tell us where the problem could be.
Get that info back to us, thanks.

 

Will do, thanks.

 

Battery @ 12.65, turned on the lights, went to start it, used both keys, each time the headlights went completely off.

 

I would suspect there is a poor connection either at the battery cable terminals or at the starter. What appears to be happening is when you place a heavy draw on the battery and the lights go out tells us the connections cannot handle the required draw. Now the poor connection could be at the battery terminals or where the cables connect to the vehicle.
Keep in mind looking at them does nothing. They must be removed, cleaned and reinstalled to assure a good solid clean connection.You may need to use a piece of sandpaper to do this right.

 

Appreciate the help brother, gonna get after all the connections again tomorrow.

 

Please also keep in mind that even you get 12.75V and a day after the battery still holds the charge at 12.75V doesn't mean your battery has the so-called cranking voltage to be able to start the car if your cranking voltage is below 9V. You should also take your battery to autozone for a bench test as well. There is something called " ", it's a tiny device for your car battery and it uses bluetooth so you can check on the voltage as long as your phone is within distance, you can keep track of your battery voltage in real time, as well as its cranking voltage history. Also note how old is your battery, maybe it's time for a new one. Another test you can do is when it doesn't start, can you jump start it with another car or noco/ctek jump starter. Like hanky mentioned, 1st thing test the cable for voltage drop, don't blindly replace a new battery if your cable(s) are bad. When you test the cable, you don't just test the B+, also test your ground cables.

 

Cleaned all of the connections, still the same.....gonna swap my battery with one out of my El Camino.

 

Here is a simple test you can do,

Clip your voltmeter leads to the battery cable TERMINALS at the battery. It should read battery voltage.
Then go to start the engine. What kind of reading do you get, need to know.