Fuel gauge problem, sender fine

[Destin Ed]

Need some help please, fuel gauge not working (below E) since I had an engine rebuild last summer - of course, they didn't cause it. But anyway, I disconnected the sender and shorted it with no change on the gauge.

The sender appears to be a reed switch type and with around 1/2 tank I see 143 Ohms on the connector so that seems reasonable. Put a DC meter on the gauge side of the sender quick disconnect expecting to see 12 VDC - nothing at all and can't be right.

Pulled the instrument cluster to find that my 2005 gauges aren't conventional - seem to be a 3 wire bus daisy chain probably from the computer. So now, what do I do? There isn't a fuse dedicated to the fuel gauge and all other gauges are working fine so this is either a wiring problem or the voltage source. Any suggestions please?

Thx, Ed

 

[scoflaw]

You need 12v at the gauge and a signal from the sender. 12 volt source daisy chains to and from all gauges

 

[Destin Ed]

On a conventional gauge that is true, I expect power and ground plus the sensor input. You can see on the images below that the center cluster has oil pressure, water temp, fuel, and trim in one package. From the back you can see the red, blue, yellow coming in and then daisy chain to the speedometer which also has and in/out set with the out not used in this boat.

Since there aren't enough wires to support 4 conventional gauges in the cluster I'm guessing this is a bus and from here I'm stuck unless I'm missing something...

 

[Lazy Daze]

I'm a bit on the fringe of my "expertise" (using that term lightly) here, but... the fuel sender, itself is a typical sender as you found out by ohm'ng it. However, instead of going right to the gauge as in a typical 12V setup, it goes to the computer and the computer interprets this and then sends the info (Smartcraft works on a 5V system) to the main Smartcraft gauge. Your tach is the main SC gauge - it then tells the other gauges what to read. If your fuel gauge (needle) is not responding, but the SC is reading correctly (digitally) for fuel, then you're looking between the SC gauge and the needle as the culprit (or the needle, itself... meaning a partially dead 4-in-1). However, if there's no digital fuel level in the SC gauge, then it sounds like the computer isn't getting the signal at all. In this case, I would start by looking at the computer on the engine and find the pink wire (which comes from the sender). It's possible it got pulled out or nicked or crimped. You could also try doing a master reset on the SC gauge - but you'll need to look in your SC manual as I don't know the procedure by heart.

 

[Destin Ed]

Lazy Daze, that is exactly what I wanted to confirm with someone who has prior experience. It seems the pink wire is a standard color for fuel sensor signals. I guess I should have included all of this in the beginning, but the main SC display is showing fuel sensor fault and it doesn't display any reading. From that, it means the computer isn't getting the signal.

Sounds like I need to locate the computer and the wire pair that goes to the sender, maybe I should only see 5 VDC at the sender since it might be coming from the computer. But either way I have to have DC on the pair that connect to the sender and I have nothing at all. Maybe I need to check for a bad ground since an open circuit is going to read E.

Thx