Fuel gauge question for anyone with an aftermarket ecu or engine swap

[Qmulus]

Originally Posted by specboxCO

I've done some more digging. On a 986 for the first 3/4 tank the cluster takes a reading directly from the fuel sensor. Once the reading from the sensor hits a certain level, a signal is triggered from the cluster through the fuel status pin #22 on the blue connector to DME pin #39. This then starts the the dme sending a signal from the fuel consump pin #83 linked to the injector duty cycle to the cluster pin #13 of the white connector. The cluster then calculates the fuel usage and displays the last quarter tank.

In short, as long as you dont go below 1/4 tank the cluster will work. Once you go below 1/4 it wont work unless you rig up a signal from the aftermarket ECU to mimic the DME.

Are you 100% on that? I know that you need to do this on cars with saddle tank, like turbos and C4Ss where the sender can't get to the bottom of the tank, but I thought that on the two wheel drive cars the cluster reads this directly.

I guess this is easy to test, I have 986, 996 C2 and 996 Turbo clusters on the bench and can just simulate the tank sender. That isn't a circuit that normally has any problems, so I have never needed to dig deep on those.