Bouncy Fuel Guage

[jedwards]

Gentlemen,
I have the aluminium tub style fuel sender in my 1967 250SL, but it remains bouncy no matter what I do and I don't seem to be able to fix it.
I have replaced the resistance wires, have them wound nicely over the dual electrical pickups on the float and have double checked the ground. I have double checked the baffle at the bottom of the tube and the tube holds fuel nicely and drains slowly, so it should be steady as rock, but it just bounces all over the place providing only the vaguest idea of fuel levels.

This should be super-easy, as the sender and the guage are simple resistance measuring items. The sender changes resistance as the float moves up or down the tube, and the gauge should just reflect that resistance.

This has been a stubborn problem and the last thing to repair on the car.
Any brilliant ideas?

[Cairns888]

Can you make a baffle for your sender to slide into before sliding it into the tank? That way the baffle you made ( with only a couple of small holes in it) should takes the spikes out of your sloshing fuel in your tank. Do you have a picture of the sender?

[Cairns888]

Does the gauge reflect what you sender does. Is it getting full scale deflexion?

[72_sporto]

Hi Jeff, Is this the same type of 3 pin tube sender as in 69-72 911s? Have you tried disconnecting the plug and using a good multimeter with sharp probes to see if the resistance is constant without the gauge connected? Pins 1 and 3 on my sender- I think that pin 4 is for the low level light only. My tank is nearly empty and reading a constant 170 ohms.