Fuel Sending Unit - Won't - Wit's End.

[Mountaineer67]

Howdy, Y'all,

Here's the short version - fuel gauge stopped working. Repair folks said to change the sending unit first because it was easier.

I pulled the old one, and they said "just make it look like the first one". Well, did that INSTEAD of reading the directions and obviously runied the thing - it never did work.

So - got ANOTHER one. Followed the directions to the letter and got it installed. It worked for about 5 minutes - then quit.

Now - thinking this was now the gauge, I started testing other things. Cleaned the contacts on the back of the gauge <check>. Made sure I was getting power back to the sending unit <check>. Pulled the sending unit out (for the THIRD time) and connected it outside the tank and moved the float - worked. Shorted the thing out to make sure the needle on the gauge pegged to full <check>. However, the minute I put the thing in the tank, it stops working and sits on "E".

The tank is 7 1/2" deep <measured it> and the float was properly adjusted for tank depth. The tank is also rather wide, so I know I'm not like getting hung up on the sides or anything.

I've been over this so many times my brain hurts. PLEASE help. Any thoughts or ideas (short of dropping a match in the hole in the tank) would be appreciated.

This is, by the way, an 88 Bayliner Capri Cuddy with a 4cyl 3.0L GM with an OMC I/O.

Thanks! I'm going to go beat myself with a hammer now...

 

[wire2]

Re: Fuel Sending Unit - Won't - Wit's End.

.... Repair folks said to change the sending unit first because it was easier. It is???

.... It worked for about 5 minutes - then quit.

Now - thinking this was now the gauge, I started testing other things. Cleaned the contacts on the back of the gauge <check>. Made sure I was getting power back to the sending unit <check>How much fuel is actually in the tank? With ? full, you should see ~6 volts at both the sender terminal on the gauge and at the sender. Pulled the sending unit out (for the THIRD time) and connected it outside the tank and moved the float - worked. Shorted the thing out to make sure the needle on the gauge pegged to full <check>. However, the minute I put the thing in the tank, it stops working and sits on "E".What's the voltage on the gauge sender terminal now? Same at the sender?

The tank is 7 1/2" deep <measured it> and the float was properly adjusted for tank depth. The tank is also rather wide, so I know I'm not like getting hung up on the sides or anything.Can you tell if the float is staying at the fuel surface as you lower it into the hole? (don't use a match to see)http://forums.iboats.com/images/smilies/biggrin.gif

I've been over this so many times my brain hurts. PLEASE help. Any thoughts or ideas (short of dropping a match in the hole in the tank) would be appreciated.Leave a voltmeter connected to tank ground and sender wire as you put it into the tank. There should be 6 volts dc +/-.
....
Thanks! I'm going to go beat myself with a hammer now...

Make sure it's a nerf hammer.
My inclination is that you have an open connection between the sender and gauge when it reads E. A meter will tell you.

 

[Silvertip]

Re: Fuel Sending Unit - Won't - Wit's End.

So here is one observation from your description: Quote: Made sure I was getting power back to the sending unit <check>. So what did you measure at the sending unit? So what did you measure ande how did you measure it. You either did not say what you meant or did something that shouldn't be done. +12 volts should only be found on the "I" terminal of the gauge. Sender resistance changes as the arm swings up and down. That varies the gauge reading accordingly. The gauge and sender shell also require a good ground. Looking at connections is not a test -- it is simply an observation. Do you have the shell of the sender grounded when installed in the tank? Does the float actually float? It may have a hole in it and be filled with fuel at this point. New or not -- "stuff happens".

Here is a diagram of the fuel gauge circuit.

 

[Mountaineer67]

Re: Fuel Sending Unit - Won't - Wit's End.

You guys are always just awesome with the information. I REALLY appreciate it. And the wiring diagram is great!

OK - not really being sure what number I should have been looking for, I set the ohm meter on 20 and, when the unit was installed and dead it would read around 4.88 back at the sender. I figured any reading meant that wiring was not the problem (yeah, I know ...but I know just enough about this stuff to probably really tear something up).

As soon as the latest one comes in, I'll try all these other things you are talking about and see where we go. The one thing I CAN tell you is that it IS grounded. It's grounded back to the panel on the dash, it's grounded to the tank itself, and I even ran a line directly to the engine block where the battery ground is attached.

If you have any other thoughts in the meantime, I'm all ears.

 

[dreamofwake]

Re: Fuel Sending Unit - Won't - Wit's End.

i know this thread is over a year old but i was wondering what ever happened. hows your fuel guage work thiese days.. im having the same problem

 

[Silvertip]

Re: Fuel Sending Unit - Won't - Wit's End.

There are now probably 75 or more posts on fuel gauge problems and most of them include troubleshooting details along with step by step instructions and resistance readings. Rather than drag up a couple year old thread that apparently didn't help you, try the SEARCH feature using FUEL GAUGE PROBLEM as keywords.

 

[dreamofwake]

Re: Fuel Sending Unit - Won't - Wit's End.

Well I am so sorry. I hope you are going to be alright silvertip. I did do a search and this is one of the threads that popped up. I guess I should've just sent a private message to the original poster cuz my question was for him to see if he ever got it working properly because we have the same boat.

 

[Silvertip]

Re: Fuel Sending Unit - Won't - Wit's End.

Yup I'm fine and I guess you are right! You should have contacted the OP. By the way, I just did a search and there are now 100 Fuel Gauge posts.