Diesel Fuel Gauge

[SawWhet]

We have a 1997 Beneteau 321 with a Yanmar 3GM30F -VDO fuel level gauge plus a combined oil pressure /engine hour meter
The fuel gauge is staying on the full mark all the time with no movement .
The gauge will show empty when key is turned off All connectors,fuse ect.at back of gauge are in good condition
Any suggestions as to what the problem is and where would I get spare parts if needed.
Thanks

[MacGyverRI]

It could just be a bad connection, clean them 1st.
Next, could be a stuck swing arm on the float but that requires taking the sender out of the tank to check it.

Some gauge senders also use a "pulse" type power supply unit (works like a turn signal flasher) to get a reading and that could be bad if equipped w/ one. The boat elec. schematic would show it inline w/ the power supply.

[Maine Sail]

Your VDO gauge is likely a standard 240-33 Ohm unit. First measure your sender to see what the OHM reading is. Simply put your meter across the center pin and the aluminum top of the gauge to measure the resistance.

If the reading on the sender never changes, bad sender.. Any Teleflex fuel gauge should easily replace that VDO or you can get another VDO gauge. Most all, unless it is one of the European VDO senders & gauges use the 240-33 Ohm scale. The gauges simply read resistance.

If replacing the sender consider a mechanical with electric capsule or WEMA type as they FAR more reliable than the standard sending units.

[BigNige]

Originally Posted by Maine Sail

Most all, unless it is one of the European VDO senders & gauges use the 240-33 Ohm scale.

My VDO sender is 3 to 300 Ohms, and the gauge reads full scale if the sender is disconnected.

[JimsCAL]

I agree with Mainesail. The vast majority of fuel gauge systems are as he describes. My guess would be the sender is since the gauge does read both full and empty. Disconnect the wires at the tank and measure the resistance with a DMM as Maine suggests.