92 with the 300 vin y. Pulled code 556, fuel pump primary circuit failure. Where does this circuit ground out? Why is it called "primary"? Is there a secondary circuit? I sure dont see one on the diagram...

 

Misfired once on me a couple weeks ago. Otherwise no symptoms. Still just wondering.

 

Without doing the research my thought is primary refers to the main power circuit feeding both fuel pumps. Secondary in my mind would be where the power branches off to each fuel pump. As I recall the pumps ground to the tank then to the frame. You should be able to verify my ideas with your schematic. Or prove me wrong. Either way I would check for power at the pumps with a multi meter and work my way back to the pcm and battery. Oh another though is the pump may be ground side switched so they would be grounded at the pcm. Again the schematic should show.

 

Thanks! Forgot to mention its a shortbox with one tank. The wiring diagram i have is for a truck with two. It shows a short line from each fuel pump to one ground point for each. Is there an actual ground wire or does the ground depend on contact between the pump and the tank?

 

Is there 4 wires at the connection? Org,pnk-blk,yel-wht and blk. Looks like the org and blk are grounded. I would trace the org and blk and see where they go. Also see if there is a ground wire by the left tail light. Don`t be afraid to just add a ground wire where it will help. The 12 volt system likes to be grounded and don`t work well at all without it. I have cleaned all my ground connections under the hood and truck because rust builds under them. I don`t think the relay has a ground.

 

I see if I can find a print

 

Thanks! I'll report back what i find /do.