I'm currently trying to repair a 1988 GMC Sierra, and I was told that I may be able to leave an existing fuel pump that no longer works in the fuel tank and add an online fuel pump externally, and that that should feed the fuel injection enough pressure to operate. Does anyone know if that's true or not?

Also, if it isn't too much trouble, would anyone happen to have a wiring diagram for the fuel system (or happen to know where one is), or diagnostic information?

I'm currently trying to repair a 1988 GMC Sierra, and I was told that I may be able to leave an existing fuel pump that no longer works in the fuel tank and add an online fuel pump externally, and that that should feed the fuel injection enough pressure to operate. Does anyone know if that's true or not?

Also, if it isn't too much trouble, would anyone happen to have a wiring diagram for the fuel system (or happen to know where one is), or diagnostic information?


just drop the tank and change the pump i had to do the same thing to my 90 stepside , it will take some time , and remember not to have a lot of gas in the tank, but it is not very hard :2cents:

if you can get a friend or 2 and an impact gun it's easier to lift the bed off. I had to change a fuel pump and i dropped the tank it took a few hours. I had to get back under there a week later and a friend helped me take the bed off and it took less then 30 minutes to get it off fix the prob. and get it back on.