Alfa Romeo Spider Late-Model Fuel Level Senders

This article was written in 1999, describing work I did myself on my car. Your car and experience may differ, proceed with extreme caution at your own risk, take your car to a qualified mechanic repair shop.

On a 1999 Old Spider Tour, I noticed a large number of Kamm tail Spiders, produced from 1971 on. The 1970’s models may have difficulty finding a suitable replacement fuel level sender, should it fail.

Important Note: When working with an open tank – sender out - make sure there is plenty of open air ventilation, and there is a strong fan to circulate air such that concentrations of vapors are reduced. When removing a sender, plug or cover the hole in the tank with a suitable item. Keep open hot (power) wires away from the open tank or residual gasoline! Disconnect all power sources, keep away any flame or spark source, use a grounding strap on yourself-to-car, and wear a VOC mask and nitrile gloves and eyewear and other protective gear.

The first order of business before removing the sender (while Battery is still connected) is to determine the sender is getting power, and the gauge is working properly. Verify the gauge is working properly first by grounding the sender wires at a safe spot (while sender is still in the tank) and noting if the gauge pegs to full. If not, use a multi-meter to check for voltage through the wire, then start checking fuses and other wire connectors through the circuit until fault is found.

Common failure modes include:

• Bad fuel tank ground, where the bolts holding in the tank have corroded such that no ground is provided for the sender. Symptoms can include a jumpy gauge needle, or no needle response at all. A solution to a poor sender ground I have been told is to run a wire from one of the small bolts that secure the sender at the top of the tank to a good chassis ground.

• Poor contact in the sender. There is a copper alloy tab inside the sender that rubs against the wire windings. The tab wears through enough that it does not contact the wire windings. Again, symptoms can include jumpy gauge or no reading at all. A common fix is to remove the sender and use thin needle nose pliers bending the tip of the tab to better contact the wires. The sender can also be disassembled by carefully bending back the three metal tabs that hold the plastic housing down. After the housing is pulled up slightly the innards are exposed for manipulation. Upon reassembly, verify that all parts are moving freely without catching or binding. The sender should be rinsed with gasoline before installing in the tank to remove any particles dislodged from the repair. Ultimately this may be an ineffective fix, and replacement is recommended.

• Broken or unraveled windings in the sender. The solution to this is to get a new sender. It would be nearly impossible to bench repair the windings and to calibrate it properly.

• Leaks from the wire connectors at the top of the sender. I discovered this when trying other used senders. Upon topping off the tank, fuel would seep through where the plastic insulators contact the sender. Not fun, as the tank is now full and must be drained sufficiently to remove the sender. Driving to lower the fuel level only increases the risk of spreading fuel in the trunk.

If the sender needs to be replaced entirely, it is probable that the proper sender for the ‘70’s Spiders are unavailable. In addition the ’71 and ’72 Spiders have a deeper fuel tank than later years (which remained unchanged in dimension). In the photo (photos now lost, will post if I find them), the left sender is a “new old stock” ’74 sender, and on the right is the original ’72 sender. Note the difference in length. My original one was worn enough at the tab in the sender that no repairs could reliably work.

I was perplexed by the long length of my original sender. I had thought that a previous owner had replaced it with another model or year of sender when I received and tried several ’73 and ’74 used senders, which were the same length as the NOS sender shown in the photo. The used senders I received worked the same or worse as my original unit, so I searched until finally finding a NOS. It worked fine, reading close enough to the original levels that there was no cause for concern, and the fuel level warning light came on at about 3 gallons left.

The NOS unit failed due to the sender windings unraveling. So, searching again to find a suitable replacement revealed several findings: A call to Alfa Parts Exchange located a ’72 sender! I indicated that if it was in poor shape they could send me a ’73 or ’74 unit whereupon I was told that the ’71 and ’72 tanks were a deep configuration different from all later years! It figures – in ’73 additional Federal regulations changes were made to the Spiders, such as the little rubber knobs on the bumpers, so perhaps there was a change in the tank for additional compliance.

Other lengthy discussions with dealers and parts suppliers revealed that the ‘80’s-on senders work perfectly as well for all ‘73-on Spiders, as they are the same length as the NOS sender in the photo. They have a fitting to hold the later in-tank fuel pump, and have three wire hookups (one ground, one hot for the sender, and one hot for the pump). They also have a fuel return nozzle fitting. To use these senders, all one needs to do is identify the sender wire hookups and ignore the pump wire hookup, and block off the fuel return nozzle with rubber hose (appropriately plugged and hose clamped) to prevent fuel leaking. The pump and sender wire hookups are very identifiable with the sender in-hand. As I’ve noted above, these senders are also close enough in length to the ’71 & ’72 length as to be usable. The price for these senders is very reasonable, and are readily available.

Before initial removal and to facilitate installation, use an indelible marker to identify the orientation of the sender in the tank, by marking on the tank where the wire connectors are facing. The sender float should be oriented at about 45 degrees from facing the back of the car if it is positioned properly (the wire connectors will therefore be facing 45 degrees towards the front of the car).

Upon installation, use the new rubber gasket provided (one should be) and secure properly. Check for leaks immediately by heading to the local gas station with car and screwdriver, top off the tank, pull back the trunk mat and check for any leaks from the top of the sender, gasket, or bolts. Tighten if needed, and re-check at intervals to ensure a proper seal is maintained.