Holley in tank fuel pump Guage inop

I recently followed some advice from on one of my FB posts and installed an EFI on my 67 XR7 289 2v. I went with the Holley 2300 with Holleys internal fuel pump 12-305. The Holley pump has 4 wires. One goes to the power feed, one goes to battery negative, one goes to the sender wire and one goes to chassis ground.

Here is the problem. Pump works, car runs etc… Fuel gauge does not work. It worked prior to the swap. The original plug for the sender has two wires…from what I can understand , one was for the sender one was for low fuel light? Anyways, no matter which wire I hook up it reads nothing. As a last chance test before I sought help, I hooked the ground wire to the other wire and it went to full, so I disconnected that, because I have about 6 or 7 gallons in it. Any ideas for me? Thank you in advance

You are right: there are 2 wires: one for fuel level and the other for low fuel warning. I hope your EFI did nothing to change these wires, although you might have a fuel return line back into the tank.

The Holly system has a line going to the sending wire? Does this pump replace the factory sending unit? If so, the problem is likely an incompatibility of the Ford gauge and the Holly fuel sending unit. If you are still using the factory sending unit, then the following applies.

It sounds like you may have a grounding issue or a bad sending unit. To test the wiring before the sending unit, pull the plug off and find the yellow/white wire. With key in ACC, briefly ground the 90* connector and the fuel gauge should go to high. Don’t leave it grounded very long at all. If it doesn’t move, your wiring between the tank and the dash cluster is bad.
Next, check the resistance between sending unit post and a good chassis ground. Should be anywhere from 13 to 73 ohms. If so, then check resistance between sending unit body and a good chassis ground: should be 1 ohm or less.
My guess is you have a bad ground or a bad sending unit.

Yes, this pump goes in place of the factory sending unit. It is one specifically for this application…well, a Mustang tank anyways. So because it is specifically for this application, as a consumer, i would hope that the compatibility wouldn’t be an issue, but…I have sent an email to Holley, still awaiting a reply. My problem is that if i ask a Holley question in a Cougar forum i have to hope I find someone thats done it. If i ask in the Holley forums, i then have to find someone thats done it with a Stang or a Cat. I suspect you are right though in that the sending unit on the assembly is bad. Or i have a bad ground, which is what I’m looking for…I don’t want to drain the tank again. UghhhHaha

Follow my tests and you can isolate the problem.