Can anyone tell me what color wires go to my sending unit on fuel tank, and which is positive and which is ground? Trying to connect an aftermarket fuel gauge.

 

Maybe. What are we talking about?

 

I’ve got 4 wires going into top of fuel pump assembly on top of tank , which color wires are my sending unit and which is positive and which is my ground. 99 Chevy express 1500 5.7 v8

 

Your factory gauge doesn't connect directly to the sender. It gets its signal from the VCM. So your aftermarket gauge may not work.

Purple is fuel level (4 to 90 ohms). Grey is pump power. Black is ground as usual.

 

I see this old thread but have a question, my fuel gauge isn’t working.

What is the VCM you speak of?
Is there a way to check
The gauge? I’d like to avoid dropping the tank, this is an RV

Thank you

 

He had a Vehicle control module. I don't know what yours has. Check https://charm.li/