fuel gauge reads Full

[pumfe]

I recently bought a 1991 Seabird Sea Core with a 90 horse Evinrude. The fuel gauge is not working, it reads above F when the key is turned on. I have checked the sending unit with an Ohm meter and the Ohms go up when the float is moved up. I have tried grounding both terminals on the back of the gauge directly to the negative terminal on the battery with no result... the needle is still pegged to the max. The only time the gauge goes to the lowest point, below E, is to remove the power or the ground. Is this a bad gauge that needs to be replaced?
Also, is there a good place to look to find a wiring diagram so I can hook everything up properly?
Thanks in advance for any advise.

 

[tbull]

Re: fuel gauge reads Full

Normally the easiest way to determine a sending unit or gauge is to take the sender wire and ground it, when you ground in the gauge should go to full, if not its most likely a bad gauge. It may be a little tougher since you said it goes to full when the key is in the on position, Try removing the sending wire from the sending unit intself and ground it, see if you get a change at all. Is it going to full when the motor is started, or just when the key is turned to the on position?

 

[Silvertip]

Re: fuel gauge reads Full

There are at least two recent threads in this forum for fuel gauge problems. Scroll down and read them and follow the diagram. If you still can't figure it out post what you have determined.

 

[BillP]

Re: fuel gauge reads Full

Typically (but not always) pegging on F is a bad ground.

 

[LiLGrady17]

Re: fuel gauge reads Full

I went nuts with mine past June. After trouble shooting the wires & replacing the gauge to boot, I found out that when tightening down the gauge to the aluminium mounting bracket, it was pivoting & causing a short by contacting another terminal.. I wound the alum bracket in elec tape, then mounted it very carefully to not contact, problems solved...

 

[Silvertip]

Re: fuel gauge reads Full

If resistance goes up when the float is raised, the float arm is installed backwards. Full up should read 33 ohms. Full down should read 240 ohms, and half way should read about 105 ohms.