There are two different types of fuel sender unit that can be fitted to the Suzuki SJ series. One has a single pin, and the other has three pins. The simplest way to establish which of the two is fitted to your car is to look at the dash warning lights. If you have a "low fuel warning light", you more than likely have a three pin sender unit. Conversely, if you have no warning light, you should have a single pin sender unit on the tank, and it will look like the picture on the left.

  

Although it makes no significant difference which type of sender unit you have fitted to your Suzuki SJ, there is one difference in the repair procedure, the "Earth" connection.

The causes ...

Fuel guage failure is usually caused by one of four things.

- bad or missing earth.
- faulty fuel sender unit.
- broken fuel sender unit.
- leaking float.

Out of the four causes of fuel sender unit failure, by far the most common cause is a lack of a suitable "earth" for the unit. Next in line is a faulty unit usually brought on by a build up of oxidisation on the windings. Next is total failure, which means the unit must be replaced, and finally a leaking float.

The repair ...

A faulty "earth" is one of the most common causes of electrical problems in any vehicle. This can be caused by a broken connector, broken or loose wire, oxidisation on a bad joint, or rust between contact points. As soon as the fault is traced, it will be easy to repair. Sometimes is pays to add an additional earth wire to the tank.

A faulty sender unit can usually be repaired. Remove the sender unit from the fuel tank, and clean the windings inside the sender unit with some fine sandpaper. Now bend the contact arm slightly so that it can make better contact with the freshly cleaned windings.

              

To check that the sender unit is working, enlist the help of a friend. Plug the connector or connectors back onto the unit as they should be, and make sure the sender unit is earthed to the SJ. Ask your friend to turn on the ignition key and watch the fuel guage as you move the float arm through the full range of motion. The guage should show ½ on the guage at the ½ way mark, etc. This will make sure that the guage is working properly or if the guage needs to be replaced because it is broken.

Connections ...

With the single pin connector, there is only one wire from the sender unit. This wire is eventually connected to the fuel guage. The earth for the sender is made via the chassis.

The three pin sender unit is different from the single pin unit because it has the earth wire connected to the unit itself. The three pin sender unit is isolated from the main chassis.

The other two spade terminal connectors are for the wire running to the fuel guage in the instrument panel, and the wire that activates the low fuel warning light. The wires are connected to the sender unit as per the diagram on the right.

The float ...

It is highly unlikely that the float will ever fail or be the cause of a faulty sender unit. The only way that this can happen is if the float should develop a leak. The solution is to repair the leak by heating the plastic with the tip of a soldering iron, or heat gun. Do not use glue of any kind, as this could be disolved by the fuel, and ultimately end up in the engine. It is however suggested that a leaking float be changed for a new one.

Warning:
Be aware of the dangers when working with fuel and sparks. Fuel vapours
 can be explosive. Together, vapour and sparks can be a dangerous
combination.