Fuel tank level sensors

[boomerang]

Right after we bought our boat in '16 ,both of the fuel gauges quit registering their respective levels within 12 months of each other. We've made do by dipping the tanks with a marked stick that the PO had onboard but a quick visual of the gauge is so much easier rather than sticking the tank so today is the day to tackle the project.
I long ago verified that it was the senders that were the culprit and not the wiring or the gauge so I pulled the carpet back, measured and cut a 4" access hole above each sending unit. There's only a couple of inches of clearance above the tanks and while it might've been possible to remove them without an access hole, it wasn't a big deal to cut them.
I pulled the first one out and saw the problem right away. Half of the float was gone and in the bottom of the tank. My first thought was "Oh crap! There must be water in the tank to have eaten up the metal float like this". I fished all around through the hole with a magnet but couldn't pull up any pieces. Then I saw that only the end of the float was fabricated from magnetic metal; the rest of the bulb was thin copper or brass. It wasn't corroded but it simply disintegrated. Weird. I can't imagine what caused it. I peered through the hole with a bright light but didn't see any pieces. The bottom was clean bright aluminum just like a new tank so I felt a little relieved and I'll just have to hope that the pieces stay in between the tank baffles and not decide to get lodged in the pickup tube aft.
I then pulled the other side and found the float bulb still intact but completely fuel of fuel.
So begins my quest for 2 new sending units.
I was able to see the number 8410 on one of the units but there seems to be another character after the "0" but maybe not. It's hard to tell. I searched 8410 fuel sending units but apparently 8410 is a John Deere tractor model number because that's what most of my hits have yielded.
I see plenty of senders but I'm not sure if all of them are the same ohm value as these and if the fastener indexing is the same size & pattern. I'll keep searching but if anyone has any insight on a replacement for these, it would be appreciated.

 

[ranger58sb]

You probably know the bolt pattern might be an SAE standard, so that might not be a hurdle.

You also probably know some common resistance ranges are 33F-240E or 10F-180E. Perhaps you can start at the gauge end and see if you can learn what it wants?

KUS (nee WEMA) makes decent fuel level senders.

-Chris

 

[ksanders]

The only senders to buy are ones made by a company called "WEMA"

They are MUCH more reliable and use the same bolt pattern that is standard for sending units.

 

[ranger58sb]

You also probably know some common resistance ranges are 33F-240E or 10F-180E. Perhaps you can start at the gauge end and see if you can learn what it wants?

Sorry, I think I mean 10E-180F...

-Chris

 

[ofer]

i gave up on all senders long time ago. a wood stick or sight tube is were its at.

 

[boomerang]

Thank you Ranger & Ksanders. The information the 2 of you gave me pointed me in the right direction & I've ordered 2 KUS SSL 11 senders. Much appreciated. I know a little about a lot of stuff marine related but fuel senders aren't one of my strong areas!
Don't worry Ranger, I was able to figure it out. If my gauge reads backwards, I won't hold you responsible...I'll just remount it upside down. Thanks again.

 

[koliver]

i gave up on all senders long time ago. a wood stick or sight tube is were its at.

Or rely on your hours of use and known GPH useage.

 

[boomerang]

i gave up on all senders long time ago. a wood stick or sight tube is were its at.

Oh, believe me, I'd love to have sight tubes but our tanks have no ports on the sides at all. The stick is fine and more accurate but having to walk out on our less than wide decks is sometimes awkward and a gauge is reassuring as a general measure while underway.
I jokingly told my wife there was no way I was going to install a little orange light that comes on when we have 50 miles of fuel left. It sometimes seems that's all that she uses as a reference when it comes to fueling our vehicles. It also seems that every time I use one of them after she's the last one to have driven them ,the orange low fuel light is on, too!

 

[ranger58sb]

Don't worry Ranger, I was able to figure it out. If my gauge reads backwards, I won't hold you responsible...I'll just remount it upside down.

 

[boomerang]

The new fuel senders showed up today ,I got them installed and they work perfectly.
Thanks again Ranger for putting my mind at ease knowing that the 5 hole bolt pattern was a standard one & thanks KSanders for recommending KUS senders. I'm sure that I'll like these senders better. They were certainly easier to install without that dumb float arm the original senders had.
Their readout is kind of different than the old senders, I noticed. They show the level on the gauge in small, multiple increments rather than the continuous, fluid motion that the senders had prior. It's just a reference so it's not a big deal.

 

[rgano]

The new fuel senders showed up today ,I got them installed and they work perfectly.
Thanks again Ranger for putting my mind at ease knowing that the 5 hole bolt pattern was a standard one & thanks KSanders for recommending KUS senders. I'm sure that I'll like these senders better. They were certainly easier to install without that dumb float arm the original senders had.
Their readout is kind of different than the old senders, I noticed. They show the level on the gauge in small, multiple increments rather than the continuous, fluid motion that the senders had prior. It's just a reference so it's not a big deal.

When I replaced my two WEMA 17-inch fuel tank senders with new (not sure why the originals quit), I cut the end off one and pulled out a 17-inch long circuit board with a magnetic reed switch soldered in place every 3/4 inch. That's why you get little jumps as you fill or empty the tanks. The water and waste tanks on my boat also use WEMA senders. Had to replace the waste couple years after the fuels. The key to not getting the waste sender clogged is complete flushing of the tank on a regular basis. NEVER leave anything in there for any length of time.

Not being able to stick the fuel tanks due to an S-turn fuel fill, I also have a sight gauge (never trust a console gauge alone), thanks to a bottom draw arrangement and a cross-feed line between them. Gauge in the center of the cross-feed line - shut off one tank at the time to find the level in the open one.

If you have top-feed diesel tanks, you can empty them one at the time to drill a hole near the bottom for conversion to bottom-feed as well as having sight gauge(s).

 

[boomerang]

If you have top-feed diesel tanks, you can empty them one at the time to drill a hole near the bottom for conversion to bottom-feed as well as having sight gauge(s).

Rich, I don't think that would work in my case and I would caution others about attempting it.
With regards to my tanks ,there just isn't enough material to be drilled and tapped for the threads to be adequately sealed. All of the fittings have an additional plate welded on top to increase the thread area & give the sealant a chance to do it's thing. A 1/4" NPT fitting is 18 TPI which wouldn't allow many threads to secure and seal the fitting with our 3/16" thick tanks. Heck, I haven't measured but ,come to think of it, they might be 1/8" tanks.
I can get by with the fuel sender not having a fitting boss under it because the 5 screws and gasket are just to stop a leak from fuel sloshing around in most cases except after being filled to the top and even then there should be little to no pressure on the gasket.

 

[rgano]

Rich, I don't think that would work in my case and I would caution others about attempting it.
With regards to my tanks ,there just isn't enough material to be drilled and tapped for the threads to be adequately sealed. All of the fittings have an additional plate welded on top to increase the thread area & give the sealant a chance to do it's thing. A 1/4" NPT fitting is 18 TPI which wouldn't allow many threads to secure and seal the fitting with our 3/16" thick tanks. Heck, I haven't measured but ,come to think of it, they might be 1/8" tanks.
I can get by with the fuel sender not having a fitting boss under it because the 5 screws and gasket are just to stop a leak from fuel sloshing around in most cases except after being filled to the top and even then there should be little to no pressure on the gasket.

A lot of folks will say you fill the empty tank with nitrogen of CO2 and weld on a thicker plate to cut and thread the hole into, but in the Navy, the machinists mates swore by https://www.belzona.com/en/products/1000/1111.aspx which we'd use to glue the hull back together when cracks developed and I have seen it used to repair damaged pump casings. Get some thicker aluminum or steel to match your tank material and glue it on with this stuff before drilling. These are just a couple of methods available to tackle the too-thin to drill and tap issue.