onan fuel pump change

[hasheel]

Kind of long post, sorry. Mine was doing the same thing. I replaced the fuel pump and filter. No gas was coming out of the fuel line when I cranked it.
After changing and reassembling. I have no 12 volt power at all! It gets better. Before I wrote this post, I cranked up the engine on the motorhome. The 12 volt system came to life. I tried to start the generator. I heard a click, and no 12 volt power. Restarted the engine, 12 volt system came back. Got the generator started.I heard a click again, no 12 volt power.
What did I do wrong?

[CloudDriver]

hasheel - replied to your PM.

I think the issue is with the house battery system, since the gen starts and everything works with the main engine running.

[j-d]

Generator is normally powered (cranked) by the House Battery not the Chassis Battery. I think a connection got disturbed in your workings. Or, house battery is discharged or defective.

[DrewE]

Is the click from the generator or from someplace else in the RV?

It could be the isolation relay between the house and chassis batteries, which in simple setups is just wired to engage when the main engine is running (by being powered by a switched circuit on the chassis). If you have 12V power only when it's on, and not otherwise, you have some open connection or fuse related to the house batteries. Check the ground and power connections there.

If it's a relay click from within the generator, I would guess there's a loose or poor connection somewhere, but the scope of the search is a bit broader: somewhere between the generator and the rest of the RV. It could conceivably also be a control wire for the remote switch (assuming you have one) shorting out intermittently.