FUEL GUAGE

redbuster · Oct 10, 2005

first off i would like to say what a great site this is. i have a gas guage issue with my 86 champion w/87 mercury. i have read as many post as i can find refering to my problem and thought i had it under control but no go. the problem is my fuel guage will not move off of empty the needle will actually go below e when i turn the key on. i have prefomed the basic test of touching the sending unit wire to the neg. battery post and the needle will go to full so i assumed the guage was good so i replaced the sending unit and still get the same reading empty, i also checked the new sending unit per instruction on other post i have read and seems to be ok. what am i missing or not doing right. thanks again for such a helpful site especially transom repair which i just recently completed,that one job i hope to never do again. bert

imported_Curmudgeon · Oct 10, 2005

Re: FUEL GUAGE

Something isn't wired properly. The gage should have a switched hot wire to (I), a wire from the sender to (S), a ground to (G), and maybe a wire for lighting. The sender unit at the tank should have a wire to ground, also (make sure the sender wires aren't reversed). Touching the sender to ground should do nothing to the gage.

Dunaruna · Oct 10, 2005

Re: FUEL GUAGE

Did you get the correct OHM range sender? Some are back to front.

redbuster · Oct 11, 2005

Re: FUEL GUAGE

thanks for the replys. i have not removed any wire from the guage so they should still be in the correct location. the new sender was purchased at a very rep.boat parts store so i assume its the correct one. the wires to the sender i am sure are correct. i thought i read and was told by the parts store where i bought the new sender that if the pink signal wire was removed and touched to the neg. side of the battery that the guage would show full. thanks again

Boatin Bob · Oct 11, 2005

Re: FUEL GUAGE

Bert...check out this page for some additional info. Sounds like you have done the basic test though and by doing it at the sender you have also checked out the sender wire to the gauge. You didn't have to run a wire to the battery neg post though, just grounding it at the tank would have been fine. Did the gauge ever work for you, is it possible it had the wrong sender in there when you bought it? and you've just put another incorrect one in? Fuel Gauge Troubleshooting

redbuster · Oct 11, 2005

Re: FUEL GUAGE

thanks Bob for you reply. the guage has worked fine for the last 14 years untill last weekend and it just quit. i've done all the usual test as mentioned with the sending unit wire and the guage will go to full so i assumed it was a bad sending unit. i replaced the sending unit yesterday and got the same result turn on key and guage goes below E. this morning i removed the guage from the dash disconnected all the wire and wired it directly to the battery and sending unit to eleminate any possible bad wiring and still get same result. so i guess i should replace the guage and hope for the best. thanks bert

gspig · Oct 11, 2005

Re: FUEL GUAGE

Have you tested the sending unit outside of the tank? Leave your guage hooked up in your dash. Remove the seding unit from your tank. Make sure the sensor wire is connected and connect the sending unit housing to the battery ground. Move the float up and down, the guage needle should move. If this works, the float is not adjusted correctly for your tank.

redbuster · Oct 11, 2005

Re: FUEL GUAGE

yes i tried that before i pulled the guage out of the dash thinking the same thing. i just can't beleive i can't figure this thing out, i'm not new to do it your self kind of stuff, i will attempt to fix just about anything and usualy can. taking things to others to fix is a rare occasion for me but this thing seems to be such a simple fix but it's kicking my a$$. i have even converted my foot control trolling motor to a hand control by relocating all the relay and such into the head unit and fabed my own handle and such but this fuel guage is crazy.

Boatin Bob · Oct 11, 2005

Re: FUEL GUAGE

Bert...I can't believe that the gauge is at fault with the test you have done. Since you seem to be pretty handy you may have some resistors kicking around at home, why not take 100 ohm resitor and try the same test but put the resistor in between the sending wire and ground, should give you around a half a tank reading on a typical gauge. If it does then I would go back to the sender again, could be even though you have the same symptoms maybe the original went bad and the one you just bought is wrong?

imported_Curmudgeon · Oct 11, 2005

Re: FUEL GUAGE

You didn't have to run a wire to the battery neg post though, just grounding it at the tank would have been fine. Not all tanks are grouded ...

redbuster · Oct 11, 2005

Re: FUEL GUAGE

bob, what is the difference between sending units when you say i may have bought the wrong one? i just called the place where i bought the guage and they say all the sending units are pretty much the same.

gspig · Oct 11, 2005

Re: FUEL GUAGE

There are 2 standard resistance ranges. Look up your fuel guage in the manufacturers catalog and it will list the resistance range needed.

Dunaruna · Oct 11, 2005

Re: FUEL GUAGE

Bert, can you confirm that you have two wires connected to the sender? You may have something as simple as a bad ground wire.

redbuster · Oct 11, 2005

Re: FUEL GUAGE

well tonite i double checked the guage by grounding the sender wire and the guage would not move to full as it did yesterday so i am going to pickup another guage in the morning and see what happens.

Boatin Bob · Oct 12, 2005

Re: FUEL GUAGE

That's odd Bert that it didn't work and I don't mean to sound dumb but I hope you had the key on or a jumper wire to feed 12v to the gauge. Whether your tank is grounded or not there still needs to be a ground wire attached at or near the sender along with the senders signal wire back to the gauge. All the sender does is act like a variable resistor between ground and the gauge.

redbuster · Oct 12, 2005

Re: FUEL GUAGE

yes i found it very odd myself, so i double cheched and cleaned all connections again and still would not swing to full as it did the day before. i went ahead and removed the guage again and hooked it up directly to the sending unit at the tank as i did the day before and still no movement. so this morning i went to my favorite boating surplus store where i bought the new sending unit and had them test the guage and found it was bad. the good news is that they have surplus guages for $10.00 so i now had a new guage to install that i know is good. wish me luck!

redbuster · Oct 13, 2005

Re: FUEL GUAGE

well for what it worth the fuel guage is working. the odd part is the only way i was able to make it work was to ground the sender to the neg. battery post instead of the common group of grounds where the original guage was grounded. also it would only work if it was grounded to the cranking battery. it would not work if grounded to the trolling battery. but at this point i'm just glad it works. thanks again for everyone help with this. bert

FUEL GUAGE

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