fuel sender ground

[dogdoc]

One of the issues I am trying to fix is the fuel readings at the helm. The main tank reading shows one bar and does not change. The aux shows and accurate reading but takes an excessive amount of time to change. I assumed it was the senders but in testing found otherwise. Shorting the aux sender contacts showed a full tank but did take to long to read. Shorting the main sender contacts still showed no fuel, ie one bar. On a hunch I jumpered the ground contact on each tank to the neg bus in the bilge and both tanks senders worked perfect in both test short and normal function from the helm switch. So far I have only inspected through the pie hole. My question, is there an easy way to run new ground wires without pulling the deck panel. I have already tried a wire brush on the tank contact/wire with no change.
thanks

 

[DennisG01]

First, check your ground bus bar behind the dash - that is another possible place for a loose/dirty ground connection (although I'm not sure if your tank ground goes to the dash bus bar or the bilge bus bar). Second, corrosion can work it way up inside the vinyl sheathing - and that could be happening at either end of the ground wire - along with the wires getting frayed/broken at the connector. Try cutting the connector off, and exposing some new wires. The wires are probably going to be black - and you can keep cutting more and more off and they'll still be black. But, take a razor blade and scrape the wires to make them clean, then see how that works. If it's now working, go ahead and put a new connector on there. If not, you've done all you can for the ground wire and you'll need to run a new one - to any ground - doesn't matter where.

 

[seasick]

The norm is for the sender ground to attach to a ground pin/terminal on the tank and the tank to have a connection to system ground. I would expect those tank grounds to join together somewhere before the run to the main ground and since you have a problem with both tanks, the issue is somewhere in the common wiring. The tank ground is important, just don't wire a new sender ground. As Dennis mentioned one place to start looking is the main ground bus at the fuse block but the ground could be somewhere else depending on where and how the batteries are wired.
Also take a look to see if you can 'see' the point where the two tank grounds are connected together and connected to the ground wire run. That is a more likely spot to develop a problem since it is often exposed to bilge moisture.

 

[DennisG01]

The norm is for the sender ground to attach to a ground pin/terminal on the tank and the tank to have a connection to system ground. I would expect those tank grounds to join together somewhere before the run to the main ground and since you have a problem with both tanks, the issue is somewhere in the common wiring. The tank ground is important, just don't wire a new sender ground. As Dennis mentioned one place to start looking is the main ground bus at the fuse block but the ground could be somewhere else depending on where and how the batteries are wired.
Also take a look to see if you can 'see' the point where the two tank grounds are connected together and connected to the ground wire run. That is a more likely spot to develop a problem since it is often exposed to bilge moisture.

Good point about the tank's ground. Dr., most likely the tank has a green wire that serves as the tank's ground. It is part of the "bonding system", which uses green wires.

EDIT: Reading back through things, this may be what you are referring to? I may have misunderstood what you originally meant.

There's no magic to this - but you MAY be able to carefully pull a new wire through by smoothly attaching it to the old ground wire and pulling the ground wire from the other end. It all depends on how many turns there are and how tightly it is tied in place along the way. But first, I'd try the cutting/scraping method. If neither of those methods used, then pulling the large hatch should make things easier for you.

 

[dogdoc]

Much as I do not want to looks like I may pull the deck panel. Boat is older and probably in need of an inspection is this area thus killing two birds with one stone. One of these days have to stop taking apart and start using this boat. Since purchased in April have had it away from the dock only once!