How to select fuel sending unit?

[CptBacardi]

My gas gauge needle sits all the way on empty and occasionally jumps rapidly to mid level and back down again. I suspect I need to replace the fuel sending unit. There are some replacement units that are the traditional “float on a lever” types and then what looks like the newer “float rides on a shaft” types. I was considering the shaft types. However, I don’t know 2 things... 1. Do I measure clearance in the tank and subtract an inch for total shaft length? Maybe just subtract 1/2”? 2. What resistance range would my original 1989 Carver gauge need? 240-33ohm seems kind of standard when I look at replacements, but how am I to know? Anything else? Thanks!

[Viper]

Knowing the manufacturer of the guage really helps but the resistance range you mentioned is pretty standard for North American applications/gauges. Again, depends on the brand though. VDO for example is a different resistance range typically.

Before replacing anything, check your connections at the tank and harness plugs, and at the gauge. Also ensure the tank actually has continuity to ground.

Depending on the shape of the tank, I usually try to keep the bottom of the sender about 3 inches off the bottom. This will give you some reserve fuel when the gauge reads empty. You should never let it get that low but good to have in case the situation creeps up on you. Of course it all depends on how low your fuel pickup in the tank is.

As far as the sender type, it's personal prefference really. You can go with higher tech stuff but the mechanical swing/float type have been around for a long time and do last for years. If that's what you have and it's original, then it's lasted 30 years, nothing wrong with that!

[g36]

Moeller makes several adjustable ones. just measure depth outside of tank order the one that covers the measurement and when you get it it will have instructions on how to customize the length and float on it for your tank.

[mbjezior]

Going through this right now too...
I replaced my fuel senders with the new WEMA sliders- tank is 22” deep- ordered 21” deep senders...Ohm 30-240...original fuel gauges are VDO...which I believe are at a different Ohm range...because I measured and calculated the exact amount of fuel in the tanks and the gauges aren’t close....ordering two new gauges that fall withing the Ohm range...will let you know..

[pepmyster]

Everything Viper said is correct, If your keeping the same gauges, match the type you have in the tank, I've replace a sender on an other boat and we used a generic one, I had to adjust the arm to get the type of measurment we needed. Good luck!

[390Express]

I'm having trouble with my gas gauges as well. (VDO gauges) The sending unit looks like it goes through about a 1.5" - 2" area at the top of the tank, with about 5 bolts through it. Do the new units fit through the old hole? And what should I expect after I loosen those top 5 bolts?

Also, if I ground the water temp gauge it pings full hot, does the same ring true for the fuel level sending unit? Trying to determine if it is the sending unit or the gauge, but I'm guessing it's the sending unit. I was going to add 20-40 gallons before I do anything. It only has about 40 gallons of gas in a 210 gallon tank right now. I figured I'd take it out with 60-80 gallons in it, and let it slosh around a bit before I change it.

[g36]

Ground the pink wire or whatever that's attached to the sender and turn on the guage it should read full. If not its the guage. Mine were carver oem guages 240-33 ohm universal need to know what yours are for sure. Yes the new sending unit should fit in the same holes, the moeller ones do anyway.the new one will allow you to rotate it to fit the float arm to a good location. If you go that type. Also There is nothing special to expect when removing the screws from the old unit you'll be pulling out the old sender and float arm just like what your putting back in.

[Midnightsun]

What exactly is your gas gauge doing?

VDO gauges work from 10-180 ohms. I would start by unscrewing the contacts at the sensor, clean/sand them and see what happens. Usually it is as simple as this. It will read empty when grounded or close to it.

VDO temp gauges when grounded work opposite of what you are experiencing with your temp gauge (323-099 ohms) and when grounded it should top out.

[390Express]

Source of the post What exactly is your gas gauge doing?

VDO gauges work from 10-180 ohms. I would start by unscrewing the contacts at the sensor, clean/sand them and see what happens. Usually it is as simple as this. It will read empty when grounded or close to it.

VDO temp gauges when grounded work opposite of what you are experiencing with your temp gauge (323-099 ohms) and when grounded it should top out.

Damn, I was hoping I could get it to move by grounding it, just to get the needle bouncing. Gauge reads dead empty, doesn't jiggle one bit when the key is one, or motor is running.

[Midnightsun]

Source of the post

Source of the post What exactly is your gas gauge doing?

VDO gauges work from 10-180 ohms. I would start by unscrewing the contacts at the sensor, clean/sand them and see what happens. Usually it is as simple as this. It will read empty when grounded or close to it.

VDO temp gauges when grounded work opposite of what you are experiencing with your temp gauge (323-099 ohms) and when grounded it should top out.

Damn, I was hoping I could get it to move by grounding it, just to get the needle bouncing. Gauge reads dead empty, doesn't jiggle one bit when the key is one, or motor is running.

Clean the contacts at the sender, may very well fix the problem.