outboard built in gas tank gauge issue

replaced a billage pump. now fuel gauge isnt working. Naturally when IM sorting through the wires to rig the billage pump im sure i created the gauge issue.

pump is an auto type, i didnt have the correct switch, I used the off on switch on the dash for manual off on, hooked the auto wire to positive side of the cranking batt pump works great,

Now Gas gauge showing needle below empty side. I did take a 12 volt test light, to the redish an black wire off the sending unit. I clipped the lead to neg. side of batt. I got a bright light on black wire.
On the reddish wire I got a low light..... so some how IM getting a back feed to the black wire,

IM desperate to repair as an outing in the back woods makes fuel monitoring critical tank is impossible to see through....

i feel certain gauge is good alog with the sending unit is as accurate as expected till I did some rewiring, please help us thanks

what color are the 3 wires coming from the bilge pump?disconnect the bilge pump completely and restore all wiring like it was...see if your fuel gauge is still working correctly...then get back to us...there is a possibility the you have the pump wires crossed at the battery ....

black, brown, brown with white stripe are the 3 wires, off the new pump, I have a mess of wires under the console, at best I can disconnect the pump wires, i changed or added, ill reply, later this afternoon, and let you know what the fuel gauge does.....

im really confused why the redish pink wire, off the sending unit is giving me a low light on my test light,
and the black lead off the sending unit is a bright light, (when I have the test light lead attached to the negative of my batt. But that all may be resolved when I unhook the new pump wires will keeep u posted

ps you may be right there was some wires disconected at the batt? Ill go through those also......will follow up

sounds like a white pump from walmart....the black lead goes to negative on the battery...i forget which of the brown wires are the auto and which is direct....find out which goes to auto switch which is probably in the pump unit....wire this to the positive post of the battery...turn the unit upside down or if it has a test knob for auto.. turn it...the pump should run when you do this....put if back in normal position...i assume now you have pump working on auto and fuel gauge working when switch is turned on at the ignition...the pump should have worked with ignition off...you have the remaining brown wire free...touch that to the positive post and the pump motor will run..you now want this wire run to a switch with positive on the other side of the switch....you can pick this positive up either after you go thru the ignition switch or a continually hot source...i prefer not to run anything that i dont have to thru the ignition switch but its up to you..i like to limit the current thru that switch..another advantage of the hot source is you can walk out to the boat and flip the bilge pump switch on without making everything hot in the rest of the boat...thats nice in the middle of the night when you are tied up at some dock...another option is to put an alligator clip on that lead and just hook it to the positive post of the battery when you want to...clip it on the battery strap when you are through..i have all my bilge pumps like this..both in campboat and fishing boat....i basically rely on the auto switches..i didnt forget the fuse...i dont have gas cans near the bilge pump and the last thing i want is for a fuse to blow when i need the pump working...its worked for 50 years for me..

You will find most fuel gauges to be notoriously inaccurate....

As far as getting the gauge to work correctly, I'd suggest starting at the gauge and working back to the tank (sender unit) since the wiring is an "unknown"... assuming the gauge is wired thru the ignition switch and uses the american standard - with key on, jumper the sender terminal to the ground terminal and the gauge should go to F...pull the sender lead off the gauge and the gauge should go to E. if that is ok, go to the sender.

For the sender to work correctly, it needs a good ground and that should be a black wire...based on the test light description, this could be one of the issues...take the pink sender wire off the sender and ground it...gauge should go to F with key on....with the sender wire disconnected from the sender and the key on, the gauge should go to E...

The only other item to test is the sender unit...and that requires (usually) removing it from the tank...the resistance from the sender wire terminal to ground will vary with the position of the float arm...about 30 ohms when the float is high and over 200 ohms with the float 'down'

if he is right about the black lead coming off the sender having voltage on it then he has 12v on the ground...i dont know if he is looking at a wire under the console or at the sender though....hopefully he just has a wiring error with no damage done an has not bumped or moved something and got a short under the console...

if that black wire is truly a ground wire coming off the sender then it could be open to ground but the i would expect to read the same on the pink wire if he is not pulling current....he says the pump is working but it could be running backward....

rickhise said:

ps you may be right there was some wires disconected at the batt? Ill go through those also......will follow up

Click to expand...

You were right there was a wire on the wrong post, disconected all batt wires and one by one figured it out, so all is good to all who took the time thanks,

next issue will be get my graph where its not getting interference from other accessory's ,,,, thanks again gauge is working, pump is on off an auto all is good