fuel tank sending unit

cc · #1 01-04-2004, 02:14 PM

I suspect the sender is all the way down when you have used 5 gallons. Sounds as if the sender length or the float arm was not long enough to allow the float to travel in an arc from full to empty as the fuel is used. If the float arm is too short, it will read from full to empty in only a very short range.

rudders_midship · #2 01-04-2004, 03:23 PM

The tank is rectangular, doesnt seem to matter if running or not, the sending unit is mounted midship,It doesnt have a mech read,with a conventional sending unit you can bend arm to adjust but this one has me wondering if it was any good from the start all connections are proper. CC there is no float arm on this unitit kinda like a post with a float that runs up and down tank size is 24"x60"x8" an exact copy of original

Scott · #3 01-04-2004, 03:36 PM

I would email or call SP ...especially since its only a year old .... That sender almost sounds like the one I was describing ....

ocuyler · #4 01-04-2004, 05:54 PM

SPTanks installed an electric sending unit in the tank they built for me. It was a reccommended upgrade. I haven't had a chance to use it yet.

I'd call SP in a minute too. But I also plan to install a fuel flow meter. I don't trust the gas guage in my truck!

EBEACH · #5 01-04-2004, 07:30 PM

I feel your pain. Last year I installed a new sending unit into my sceptre, and it doesn’t work. Unfortunately, the screws holding mine in place are just about stripped out. I’m not going to open that can of worms. I’ll be installing a fuel flow meter that Santa gave me.

Regarding your problem, I’d think that most of the sending units are a resistive type, and you could check it out with a volt meter. Call SP, and ask about the type of output. If resistive, ask them how many ohms it should be when full & empty. The gauge may not be compatible, or it may need to be tweaked

rudders_midship · #6 01-05-2004, 01:06 AM

Last year I had fuel tank built by SP tanks the tank came with a sending unit installed it has a shaft and float assembly (vertical) the problem is the gauge will read full when full, but about 4 or 5 gallons aprox into a trip it goes to about half and when reading empty it still has about 21 gallons left in tank (50 gal tank). Should I go to the more conventional sending unit (rod with cork float) or is my gauge not compatable with SP type sending unit. Any help would be helpful since boat is in my shop ready to do minor fixes and improvements.

Scott · #7 01-05-2004, 01:47 AM

Whats the shape of the tank ...and does it happen when running or do you get the error when the boat is standing still?? If it’s a rectangle and the unit is mounted more towards the front of the tank all the fuel will “run” from the sender when under way ….but I doubt that’s the case with your tank….they are usually in the midsection
What did SPtanks say about it ?? you might just have a bad sender/bad connection … Does the sender have a mechanical read on the sender itself and if it does …does it read the same as your electronic gauge??? You could also pull the sender and measure its resistance to see if its faulty…for that matter pull it and swing the float up and down to see if the gauge moves on your console …..

Those guys at SP showed me a new sender ( I think magnetic) that looked really nice .... but more expensive....no float like the typical sending unit ... and to install you need clearance above the tank equal to the length of this sending unit... they made it out to be a very reliable sender ....Who knows....