Yamaha Guage question

[MechanicMike]

I running a 2000 model year Yamaha ox66 150 on my Grady White 209 escape with Yamaha didgital guages. At the end of last season the fuel guage would intermittently read low fuel with the bottom bar flashing. Launched the boat this weekend with a full tank of fuel and its reading empty. Before I order a sender I would like to confirm the wiring and guage are not at fault. Is there any place to get a wiring diagram for the Yamaha guages? I would like to figure out which wire(s) are for the fuel guage.

Thanks
Mike

[boscoe99]

The white wire from the speedometer is for the tank level input. It will normally connect to a pink wire that runs to the fuel tank sender.

The gauge very rarely fails. Wires can fail or connections can be compromised but usually it is the sender that is at fault.

Gain access to the fuel tank sender. Remove the pink wire. The gauge should go to empty and flash the bottom bar. Connect the pink wire to ground. The gauge should illuminate all of the bars.

If the sender is found to be defective (about a 100% chance) then install this one

CENTROID PRODUCTS - Computerized Tank Display - Electronic Senders - capacitive fuel gauges

[MechanicMike]

Great, thanks for the reply.
Next question.
Whats the chances of the sender mounting screws coming out in one piece or at all? Any tricks other than a good penetrating oil and some luck? Thanks for the info

Mike

[boscoe99]

Biggest problem I have with Phillips head screws is the bit backing out of the head of the screwdriver. Just use whatever pressure is needed to keep it from backing out. They make bits that have a rough finish so hopefully they stay in the head of the screw.

Also, in the case of my boat the screws came right out, it was just a bitch getting to them. The sender was not located directly under the deck hatch.

Good luck with yours.

[TownsendsFJR1300]

Plus 1 ^^^.

I would, BEFORE pulling the sending unit, check remove and clean, etc, (just don't look at them) all the wires going to the sender.

Its very possible just a bad connection up above at the sending unit.

Good luck and please post what you find/fix..

BTW, should the sender have to come out, they make a hand held impact screwdriver tool. Put the proper bit in it, give it a smack. The tool keeps the bit from skipping/jumping out and you get the "shock" to hopefully break the screws loose. If thier really old, they may break... Lots of penetrating oil won't hurt either

See below link:
http://www.sears.com/craftsman-impac...p-00947641000P

[tmann45]

When testing as Bosco explained

Gain access to the fuel tank sender. Remove the pink wire. The gauge should go to empty and flash the bottom bar. Connect the pink wire to ground. The gauge should illuminate all of the bars.

give the gauge a minute or two to react, the damping is extreme.

Impact are great tools, but I would be careful using it on the top of a fuel tank, too big of a hammer could cause some undesirable results.

[boscoe99]

When testing as Bosco explained give the gauge a minute or two to react, the damping is extreme.

Good point. If someone is expecting an immediate reaction from the gauge based on the speed of the electrons they could be fooled by what is being seen on the bar scale.

[MechanicMike]

Finally got back to the boat yesterday. Looks like a bad ground is the culprit. I grounded the pink wire at the sender and the gauge read full. Theres a ground wire at the tank that pigtails into the sender harness. When i ground that wire with everything connected the fuel gauge was reading 3/4 of a tank which is about right. I just need to figure out where the gauge harness gets its ground from. The black wire off the sender harness runs with the pink wire and disappears under the floor. Assuming it goes into the console someplace but i will need to look further
Thanks for the help
Mike

[boscoe99]

Generally the sender will be grounded at the tank. There is usually a wire that runs from the sender (and the tank) back to the ships ground bus.

Ground is ground is ground.

[TownsendsFJR1300]

Glad to see it was indeed a simply ground wire..

[rodbolt17]

if you have a metal tank the no ground isn't ground.
ALL metal parts including metal fuel fills MUST be bonded typically a green wire.
the bonding system is NOT designed for current carrying its desined to bond all metal parts of the system to a 0 potential.
yes it all goes back to the negative terminal but bonding and grounding are 2 different circuits.