fuel gauge always reads full

[cousinabe]

My multifunction gauge always reads full. this did not happen last season.

I have twin 1997 Yamaha 225 SWSII EFI engines. the two tanks/sending units are wired to a switch(port/starboard) which wires into the single multifunction guage.

can both sending units be bad?
when i disconnect the pink wire to the gauge, it goes to empty.

The sending units have two wires coming out.
the selectable switch directs the pink wire to the gauge.

http://www.boats.net/parts/images/6Y5-83570-S5-00_lg.jpg

any other tests with voltage/ohm readings i should do?

 

[jtexas]

Re: fuel gauge always reads full

keyswitch on, touch one end of a jumper wire from any good ground to the pink wire terminal on the gauge - it should jump to E. That'll the confirm the gauge isn't getting a signal. Now ground the terminals on your selector, each in turn. Grounding the terminals should peg the gauge to E, if it does, that sender or the wiring is faulty. If it doesn't, the switch is at fault, or the wiring from switch to gauge.

A good inspection, cleaning and tightening of all the connections might fix it - corrosion sets in, things vibrate loose, wires break, etc. Might want to think about going over all our wiring as a preventive measure.

 

[cousinabe]

Re: fuel gauge always reads full

j, thanks for the reply.

So I grounded the pink wire on the gauge and it jumped to FULL. Not what I thought it was supposed to do.
Does this confirm that it is my gauge?

Thanks.

 

[rickdb1boat]

Re: fuel gauge always reads full

From teleflex site:

Test the gauge’s operation by doing the following: Connect a “hot” wire to the “I” terminal and ground wire to “G”
terminal. Take the sender (usually pink) wire off back of gauge . Gauge should read below Empty. Next, add a short
wire from the gauge’s “S” (sender) terminal to ground. Gauge should read above Full. If the pointer sweeps back
and forth, the gauge is OK.
3. The sender can be tested by checking its resistance with a volt/ohm test meter (use analog meter).
Remove sender (usually pink) wire from sender .
Connect two test meter wires to two sender terminals (or center terminal & flange if sender has only one terminal).
Move float arm by hand. Approximate values:
Empty = 240 ohms, 1/2 = 103 ohms, Full = 33 ohms.
(Not all Fuel Senders have the same resistance range. Marine units, either boat-builder installed or pur
chased at marine stores, are 240-33 ohms. Non-marine units may be 0-90 ohms, 73-10 ohms or some other value.)​

 

[dingbat]

Re: fuel gauge always reads full

I had the same problem a few weeks ago and it turned out both senders went.

Try one thing first, remove the pink wire from the tank select switch and jumper it directly to the pink wire running to the gauge. On my last boat I had a similar thing happen and it turned out that the switch went bad and grounded out the senders.

 

[jtexas]

Re: fuel gauge always reads full

sorry, guess I got it backasswards, or else some gauges are different........

 

[cousinabe]

Re: fuel gauge always reads full

Problem solved.
Turned out both sending units were bad. The floats on both ISSPRO sending units were stuck near the top even when the tanks were near empty.
Not sure if ethanol was the culprit.
http://www.isspro.com/proddetail.php?prod=RA9506-ISS

I replaced them with WEMA sending units which have the floats on the outside rail.
http://www.wemausa.com/tank_sensors/details_SSS_SSL_tank_sensors.htm