Fuel gauge for port tank not working on my 1996 Bayliner 3388, what to do?-gctid827772

[hodaka]

On my 20 year old Bayliner 3388, there are two 100 gallon aluminum fuel tanks outside the Cummins 4BT diesel engines. Both fuel gauges worked fine for a couple of years after I purchased the boat, and presumably before that. Then a couple of months ago the port side gauge stopped working, and constantly reads zero fuel, no matter whether the tank is full or 1/2 full or 1/4 full. Not a big problem during our 2-1/2 month trip, as the starboard gauge continued to work, both tanks started out equally full, so I just used the starboard reading for both tanks, as the diesel engines historically consumed fuel at the same rate.

When the port start engine key is turned on, the fuel gauge indicator does very slightly move -- it jumps about 1/8 inch, and stops below empty. Even if the tank is full or partially full, same thing. I tried using some electrical spray stuff on the two port fuel tank connections; that did not help. Then I tried removing the nuts that hold the wires to the fuel gauge sending unit on the port diesel fuel tank, cleaning them, and reconnecting; same problem. Uncrewed the gauge cover panel just below the helm, all connections to the port side fuel gauge look good.

A pic of the port tank top sender unit is below. The 5 screws on top don't want to come off, seem to be round, or rounded with age. May have to try vise grips, or maybe something else?

I suspect the 20 year old port sender unit has failed, but how do I test this stuff to determine if (1) the fuel sender unit has failed, or (2) the fuel gauge has failed, or (3) maybe a wire has shorted out, or (4) something else. I do have a multimeter, but diagnosing electrical troubles is definitely one of my weaker skills. All thoughts/comments/suggestions welcomed.




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[TenMile]

You could try reversing the fuel leads at the gauge. Switch the leads from the non-working gauge to the working gauge. That will eliminate a faulty gauge as the issue.

Like you've said, it's highly likely that it's a faulty sender unit. To remove the bolts, try getting some stuff called Kroil. It's a highly effective penetrating lube. Put it on, let it sit -- give a couple knocks with a hammer. Repeat.

Being a guy who owns one of these, hopefully there's enough room at the top of the tank to remove the old sender unit. I suppose if the sender is the older style float/arm it should come out without having to tip the tanks over.

PS: if you're going to do one -- might as well do both....