My Carter fuel pump, that was backing up my stock left pump on the fuel filters, started making some strange sounds, so I decided to change it out, (it was installed in 2005). I've had this new Holly black for years now, so in it goes. I also had a adepter so I removed the stock left pump at the same time. Now I was going to connect the wires from the stock lift pump to the Holly. I cut the plug off the end and was going to add a extension wire down to the Holly pump but put a meter on it first and it only read 7.5 v. This was no good so I ran a new wire out of the fuse box. The Holly works fine. Always reads 17-18 psi at start-up, at wow and towing goes down to 11-12. But now I've got this code. P 0628 fuel pump control circuit low. What is this from and what do I do? Also, how come it only read 7.5v at the lp?

 

The computer needs to see a light load on that 7.5 vdc. I installed a tail-light bulb soldered together a twisted elect wire to make a pin out of the leads and plugged it into the connector. (you already cut it off. ooops) The computer will NOT throw a code if done this way. Attach a ign switch-on power connection to your fuel pumps so they come on when the keys on.
Should be fine then.

I did quite a write-up and you can follow it here. Download the pdf and read up on the reason, how i did it and why here: post no#5

https://www.dieseltruckresource.com/...d.php?t=191118

 

Thank You, You've been very helpful, I'm going to install a light bulb socket with bulb under the hood. Thanks again.