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Does Sulfer in Gasoline corrode sending units?

Recently I bought a used boat, the previous owner neglected to tell me that when the gas gauge shows 1/4 full, the tank is in fact empty. Needless to say I ran out gas at a most inopportune moment.

When I described to a fellow boater while in a lock, he said it was due to the high sulfur content that used to be present in Canadian gas and that it corroded the “silver” wires on the sender unit.

I doubt the wires are actually silver, I’d think Nichrome more likely, that aside, is there any truth to this theorem?

I do think that sending units can send out an incorrect signal and the cause of this incorrect signal is an incorrect resistance at the contact wires but if high gasoline sulpher content is the cause I just don’t know

They’re typically corrosion proof for gasoline. Some are adjustable to accommodate various tank depths. Pull it and look. You can check the resistance across the range then as well, typically 30-240 ohms, full to empty. A new sender is <$50.

Problem is that it’s a first class PITA to get to the sender, I’d like to know for sure whether its a corrosion problem, that can be be fixed with the use of something like injector cleaner in the tank, (as was suggested by the guy who “diagnosed” my problem while rafted up to me in a lock on the Rideau Canal)

I have heard that a good-quality fuel system cleaner, like Chevron’s [b]Techron[/b], can help to clear sulfur deposits from sending units.

Can I verify this through personal experience? Nope!
However, running a couple of bottles of Techron through your fuel system would be a relatively low-cost solution, so I would suggest that you give it a try. If it doesn’t work, at least you will only have spent…about $10 or less.

Thank you, so you have heard of sulfur deposits on fuel senders!

Of course this is a pretty big tank, compared to cars, 250 litres, near 70US gallons. Might take more than a bottle or two!

Yes, I have heard of sulfur deposits on fuel sending units, and I have also heard that this is a particular problem with certain GM models.

The real fact is that a boat fuel gauge is never accurate. The boat is constantly pitching and rolling. Was the sender installed and the float adjusted when the boat was on a trailer, in dry-dock, on blocks, or in the water? All these will read different as the boat will be at different degrees of list (off level side to side) or pitch (off level bow high or low). I have had more than a few boats and learned if the gauge reads anything under 1/2 you need to be looking for a fuel dock.

If I had one gauge that worked I would be happy. After 10 years and no gauges I have an opaque gas tank to watch levels on, looking for the water stream from the engine to make sure impeller is working, Listening for sounds of problems, no temp, no tach, no gas gauge, no depth gauge, no speed gauge, and no other gauge I am not sure what it does, I have put a little time into looking at them but not enough, we water ski tube and fly like the wind, we don’t need no stinkin gauges! 1985 boat, after 25 years oh well.

There Have Been A Few Different Problems Involving GM Gas Gauge Senders (Sensors).
Problems have been seen in wiring, and floats on certain models.

Some manufacturers recommend Chevron Techron To clean corrosion from the the “wiper” and circuit card parts of the sensor. GM says that corrosion of fuel sensors is caused by abnormal levels of sulfur in gasoline sporadically occurring in certain parts of Canada and U.S.

I have personally seen Chevron Techron used to clean the contacts and not have success because the “corrosion” actually disintegrated the “fingers” on the wiper. The wiper no longer made normal contact with the circuit car because part of the metal fingers were just plain gone. I have examined the parts and can verify this disintegration.

One should give the Techron a try first before delving into testing and removing parts. The Techron bottle I believe says that it is used for cleaning fuel sensors.

There are several reasons why the boat’s gauge could stop reading correctly (a few mentioned above) and corrosion could be one. Follow directions on the Techron bottle and give it a try.


Thanks so much all of you guys, I’ll try to find Techron, hopefully someone in Canada carries it.

Yeah, I have a 15’ runabout with gauge that I have grown familiar with, one has to learn to judge the true levels between the swinging limits of the needle. This new boat is pretty big, 25’, and I was driving on basically flat water, the needle slowly falling across the course of two days, I’ll try the Techron, keep a spare jerry can with me and see what happens.

When talking used boats you never know what you’re dealing with. Marine senders are built better than automotive senders but you have no idea what the previous owners did. There are at least two styles of sender one is beam float and rheostat the other is linear float and completely enclosed sensor. Can’t hurt to try cleaner but wouldn’t be surprised if no joy. Have several boats and familiar with being contortionist to access parts. Alternative could recal gauge range to match sender output. …

The last sending unit I replaced this is what I did. pumped the tank dry or nearly so. It had a 50 gal.tank so I put in 30 gal. put the boat back in the water. Adjusted the the float to read 1/2 tank. with the boat in the water normally loaded. This way I had just over 1/2 when the gauge read 1/2, leaving me a little cushion.

Given that running out of gas in a boat can be (rather substantially) worse that running out in a car, does it make sense to bet your life on the accuracy of a fuel guage?

Were it me, I’d do what I did when flying GA (again, an application where running out of gas can be bad):

  1. Make some sort of stick to measure the depth of the fuel in the tank. Calibrate this stick to # of gallons in tank via filling of the tank.
  2. On the next few times you have the boat out, keep track of hours’ operation (at a given power setting) and compare to fuel subsequently taken on board to get a baseline fuel consumption.
  3. Once you have a pretty accurate accounting of fuel burn, “stick” the tank before leaving, and consider hwo many hours’ operation that gives you. (Allow a decent reserve capacity.)
  4. When filling up, note gallons of reserve fuel (easy if filling up) and see if you ate into your reserve. If so, re-calculate 1-3 as needed.

Yes, high supphur content in gasolines has caused failure of connections on fuel sending units.

Re High Sulpher Content Gasoline Products Liability Litigation, MDL No. 1632, In the U.S. Distict Court For the Eastern District of Louisiana, PSC and Co-Lead Trial Counsel, class settlement for $99M. - Sept. 2006
SAMPLES v. CONOCO, Case No. 88016 in the Circuit Court for Escambia C ounty, Florida , $90 M settlement Nov. 2004.

There have been a number of other class action suits re: high sulphur content in gasoline. But I have no way of knowing of that’s the cause of your boat’s gas gage inaccuracy. Normally the corrosion causes total failure of the circuit. My guess is that your sender float is misadjusted or hanging up.

Interesting, I haven’t had a chance to try the cleaner yet, I’ll yet everyone know after I try it.