Fuel gauge question

[AZcamperguy]

Yeah, I know this seems to be a common topic. I have read dozens of threads by searching but I am still confused. I have the diagram saved.
Here's my deal. I got the boat used. The guys said he couldn't figure out why the gauge didn't work.
A friend suggested the float may be stuck and that I should add something like seafoam and see if it works. I did this, filled the tank and away we went. Later, the gauge appeared to be dropping some. After a couple of short trips, the gauge now reads full anytime I turn the key on and slowly drops to empty when the key is turned off.
So, it appeared to be working for a bit and now seems to go to full and stay there. Is it possible that the sending wire is touching a ground somewhere? this pegs it to full right?
Again, I did search and don't really understand. I appreciate any assistance you can offer.

 

[Silvertip]

Re: Fuel gauge question

You've done no testing using the many responses. Anything is possible. If the float is hung up SeaFoam is not the solution. If someone torqued the pink wire connection on the sender too tight it is possible the sender is shorted to ground internally. That's been covered as well -- with pictures. The sender must measure 33 - 240 ohms (full - empty) which testing has also been covered a multitude of times. Testing of the gauge itself was also covered many times. Until you test things, it is anyones guess.

 

[AZcamperguy]

Re: Fuel gauge question

Well, I honestly haven't read every thread on here but have read several. I haven't had time to test things as of yet and would prefer to understand what I am doing before I start messing around with electrical things and gasoline. I have a tendency to get shocked when people say I shouldn't. I've learned to take more time with these things. Hopefully in the morning I can look to access the sending unit.

My first question is regarding the tank going to full when the key is on.
Possibilities are
1. Float stuck
2. Pink wire getting grounded somewhere
Does this sound right?
I am trying to eliminate things slowly and safely as possible. Is there another reason the gauge would show full when the key is on and I know the tank is not full?

Here is the diagram but I have seen no pics of a sender shorted to ground internally.

 

[Silvertip]

Re: Fuel gauge question

Do you have a multi-tester (volt/ohm/milliammeter) and know how to use it? Troubleshooting electrical issues requires a "logical" approach rather than just looking at what might be wrong. Without a volt/ohm meter you will end up a frustrated individual and will have bought new parts that you probably didn't need. That diagram is one that I created. Wherever you copied it from very likely had troubleshooting procedures. If not that particular post, that diagram has been posted many dozens of times with the testing procedure. The SEARCH feature will turn it up.

Shorted internally: Below is a picture of the sender. See the nut at the top that secures the pink wire? turning that nut too tightly causes the connecting wire under the flange to twist and short to the framework of the sender. Hence you "shorted" the sender to ground. Without removing the sender, an ohm meter would verify that is or is not the problem. Using an ohm meter to check the resistance of the sender (pink wire disconnected) would show either 33, 109 or 240 ohms (full, 1/2. empty) depending on how much fuel was in the tank. Any number greatly different than that indicates a bad sender. Without an ohm meter the only other test you can make is to MOMENTARILY short the send wire to ground and see if the gauge pegs full. All that proves is that the gauge is functioning. If it doesn't, it does not mean the gauge is bad. The gauge may not be getting +12 volts when the key is on or it may not have a good ground connection. Again, without a volt/ohmmeter you can't make those checks. A meter is less than $15 at any home improvement store.

 

[AZcamperguy]

Re: Fuel gauge question

Do you have a multi-tester (volt/ohm/milliammeter) and know how to use it? Troubleshooting electrical issues requires a "logical" approach rather than just looking at what might be wrong. Without a volt/ohm meter you will end up a frustrated individual and will have bought new parts that you probably didn't need.

Right, I am trying to avoid unnecessary work and parts which is why I am asking questions and reading up on it. I do have a meter and kinda know how to use it. There are things that I don't quite understand though.

That diagram is one that I created. Wherever you copied it from very likely had troubleshooting procedures. If not that particular post, that diagram has been posted many dozens of times with the testing procedure. The SEARCH feature will turn it up.

I have searched, and I have read the procedures, however I don't think I understand them which is why I posted this thread. Trying to understand.
In the procedure you state that one should ground the pink wire with the key in the on position to see if the tank pegs full. The thing is, my tank pegs full as soon as I turn it on. That's why I was asking about the possibility of there being a grounding issue with that wire? If it is already pegged to full how is it going to look different if I ground the pink wire?

Shorted internally: Below is a picture of the sender. See the nut at the top that secures the pink wire? turning that nut too tightly causes the connecting wire under the flange to twist and short to the framework of the sender. Hence you "shorted" the sender to ground. Without removing the sender, an ohm meter would verify that is or is not the problem. Using an ohm meter to check the resistance of the sender (pink wire disconnected) would show either 33, 109 or 240 ohms (full, 1/2. empty) depending on how much fuel was in the tank. Any number greatly different than that indicates a bad sender. Without an ohm meter the only other test you can make is to MOMENTARILY short the send wire to ground and see if the gauge pegs full. All that proves is that the gauge is functioning. If it doesn't, it does not mean the gauge is bad. The gauge may not be getting +12 volts when the key is on or it may not have a good ground connection. Again, without a volt/ohmmeter you can't make those checks. A meter is less than $15 at any home improvement store.

Thanks for the pic. I am not sure how much fuel is in the tank currently because the gauge doesn't work I will fill it again tomorrow and take it out on one trip. I guess I can guestimate from there. I will post numbers at that time. Also, I will take off the access panels and see if I can see the sending unit tomorrow. Thanks for the help. I'd love to have a working fuel gauge

 

[AZcamperguy]

Re: Fuel gauge question

Here is a picture of my sending unit. Doesn't look like the one you posted.....

So I cut the pink wire and put the meter on the pink wire coming from the sending unit. I touched the other lead of the meter to the metal housing of the sending unit and got nothing.

 

[AZcamperguy]

Re: Fuel gauge question

Looks more like this one doesn't it? http://www.iboats.com/Moeller-Reed-...7004435--session_id.532211134--view_id.368241

Also Silvertip, why don't you have them add your nice diagram of the fuel gauge and sender to the sticky at the top?

 

[Silvertip]

Re: Fuel gauge question

Here is a picture of my sending unit. Doesn't look like the one you posted.....

So I cut the pink wire and put the meter on the pink wire coming from the sending unit. I touched the other lead of the meter to the metal housing of the sending unit and got nothing.

I assume you had the meter set to read "resistance" (ohms) and not voltage. So that says the sender is bad. However an OPEN circuit (ultra high resistance) would case the fuel gauge to read EMPTY -- not FULL. So something else is wrong. When you had the pink wire disconnected, why didn't you turn the key on and see what happened. When testing things that "change" or "stay the same" mean something. And just because sender LOOK different doesn't mean they operate differently. Your car looks different than your neighbors but both will carry you to the store -- not???? Yes, some senders have three wires. Yours does not. Did you check to make sure the black wire is grounded to the neg terminal on the battery?

 

[Silvertip]

Re: Fuel gauge question

Looks more like this one doesn't it? http://www.iboats.com/Moeller-Reed-...7004435--session_id.532211134--view_id.368241

Also Silvertip, why don't you have them add your nice diagram of the fuel gauge and sender to the sticky at the top?

The moderators are very welcome to STICKY any diagram or procedure from anyone. The problem as I see it, people don't read the stickies nor do they use the search feature so what's the use. A classic example is in the PROPELLER forum. About half the people do not look at the READ THIS FIRST sticky that explains what's needed to provide help on prop selection. Without those numbers we simply can't help so I've basically quit posting on that forum. When Engine rpm at WOT is asked for and someone says they don't have a tach, what are we supposed to do? It gets real old having to repeat this time and time again. In that particular case I've asked that when someone clicks on the PROPELLERS forum, the first thing that pops up is a full page note saying something like: YOU NEED THE FOLLOWING INFORMATION TO GET HELP WITH PROP SELECTION (followed by WOT RPM (observed), current prop (diameter/pitch/aluminum/steel/3-blade/4-blade/2-blade etc), current speed, current engine and lower unit gear ratio). NO TACH, NO HELP.

 

[AZcamperguy]

Re: Fuel gauge question

I assume you had the meter set to read "resistance" (ohms) and not voltage. So that says the sender is bad. However an OPEN circuit (ultra high resistance) would case the fuel gauge to read EMPTY -- not FULL. So something else is wrong. When you had the pink wire disconnected, why didn't you turn the key on and see what happened. When testing things that "change" or "stay the same" mean something. And just because sender LOOK different doesn't mean they operate differently. Your car looks different than your neighbors but both will carry you to the store -- not???? Yes, some senders have three wires. Yours does not. Did you check to make sure the black wire is grounded to the neg terminal on the battery?

Well, I certainly appreciate you taking the time to help people like myself. I do try to fix things myself whenever possible but with zero experience, some things are harder to grasp.
I set the dial to ohms but was not aware of a difference otherwise. I will wait until my friend gets back into town tomorrow to troubleshoot further. He understands electricity far better than I.
I didn't turn the key on because I didn't think to. It is a good suggestion.
I didn't think that the sender operated differently because it looked different, I was simply pointing out that it was different and that there was no screw by which it could be grounded from being turned too much. Simply eliminating that from the potential causes
I haven't ripped everything apart again to follow the wires because I am going fishing tonight. I will take the everything apart again tomorrow and see if my buddy can help me with the meter and make sure I am doing it right. I will get back with you again then.
I appreciate your patience and knowledge Silvertip.