Close up of vehicle fuel gauge pointing to empty
Taking fuel reserve technology to new levels.

Better miles-until-empty innovations: meet our high-accuracy fuel level sensor.

We all do it. We look at our fuel gauge hovering above “E” and decide to run it as far as we can before we fill up. The reasons vary: Late for work. Too cold or too hot to stop. Don’t want to pay that price for fuel. And so on. As drivers, we’ve come to rely on that wonderful “miles-until-empty” readout on the dash to help us navigate these reasons and not wind up stranded on the side of the road.

Now, if you’re a fuel system engineer, you’re well versed in this behavior and the complications associated with designing for it – and around it. They include:

  • Enhancing in-tank, fuel-level sensing to ensure “miles-until-empty” accuracy and long-term durability.
  • Finding ways to reduce on-board fuel reserves in order to cut vehicle weight to hit fuel economy targets.
  • Containing costs, while also boosting quality and continuing to deliver great ownership experiences.

Easy enough, right? Well actually, it is, if you turn to Delphi Technologies and our fuel delivery modules with our High Accuracy Fuel Level Sensor.


First and best.

This latest fuel system advance from Delphi Technologies features a redesigned float arm, wiper assembly and sensor card that beats the competition in durability, costs, accuracy and manufacturability. And, when compared to previous generations of our modules, these first-to-market innovations:

  • Improve fuel level precision in low fuel situations by an amazing 67 percent.

  • Reduce fuel reserves by 50 percent.

  • Boost durability and reliability by 100 percent.

  • Deliver a 29 percent reduction in costs.

Combined, it all adds up to less vehicle weight, better fuel efficiency and increased driver satisfaction with fewer fill ups and more accurate “miles-until-empty” readings over the life of the vehicle.

Vehicle fuel tank with reserve area filled to the top
Before: Many automakers are pursuing ways to cut vehicle weight by cutting fuel reserves. Doing so, though, requires more precise means of measuring reserve levels.
Vehicle fuel tank with 50 percent less fuel in reserve area
After: Our High Accuracy Fuel Level Sensor enables reserve reductions of up to 50 percent, which automakers can convert into less fuel in the reserve, smaller tanks or increased range by moving reserve fuel space to active fuel space.

The backdrop. 

Before we get into how we redesigned the module, let’s dig a little deeper into some of the challenges associated with fuel reserves.

It’s no secret that our customers worldwide are actively seeking ways to reduce vehicle weight in order to improve fuel economy and reduce emissions. As part of this push, we know you’re seeking better ways to manage on-board fuel systems, particularly fuel reserves. The reserves are what’s left in the tank even when the gauge reads “empty,” and are needed to avoid the damage that can occur from completely draining the tank. 

We know you want to reduce these reserves yet have been reluctant to do so given the fluctuations that can occur with in-tank fuel level readings, especially over the life of the vehicle. It’s just better to have the extra fuel on board than risk system damage.

Additionally, given the owner-facing nature of the “miles-until-empty” prompt, many of our customers have increased the durability requirements of fuel-level monitoring systems. In the past, durability tests of 2-3 million cycles were the standard. Today, to be certified for use, cycles of 5 million-plus are the norm.

And then there’s costs. We know you want to boost accuracy and improve durability without an increase in costs. Simply put: You want it better and at a lower price point.

These were the key factors we took into consideration as we set about to create our next-generation fuel level sensor.

The perfect combination.

First, the float arm. The arm resembles a wire coat hanger with a mini life preserver, known as a float, at the end. The float rides on top of the fuel, causing the metal arm to rise and fall with the fuel levels. The arm, attached to the wiper assembly on the fuel module, rocks back and forth across a sensor as fuel levels go up and down. 

Seems simple enough. However, in order to work, the float arm needs to conform to the tank. As tank sizes and shapes vary, the arms are often twisted and turned in order to fit. The more bends you have in the arm, the greater the potential for problems with accuracy. Complicating matters further, the contorting of the arm often takes place during final assembly when the module is installed in the tank. This not only risks accuracy but introduces the potential for damage.

Our engineers explored the angles and determined that the best path was to convert the top, or the vertical portion of the float arm, to plastic. Using plastic:

  • Eliminates bends and reduces variation in height, which impacts sensor accuracy, to +/- 1 mm verses the industry standard +/- 3mm.

  • Reduces costs via less expensive materials.

  • Allows for improved out-of-the-box use across different tank configurations.

  • Minimizes the need for changes during final assembly, reducing manufacturing time and costs.


Fuel delivery module with float arm in plastic
With our redesigned module, we converted the top of the float arm from metal to plastic. This cuts costs and improves out-of-the-box use across multiple fuel tank configurations.

Second, the wiper assembly. The assembly houses a frame and ceramic sensor card. The float arm attaches to this assembly, moving back and forth across the sensor card to transmit fuel-level readings to the system. Most assemblies use redundant contacts and ground planes, or conducting surfaces, to complete the circuit. Over time, however, these contacts can wear, weakening current flow and compromising fuel-reading accuracy.

Our engineers knew the best shot we had at bettering long-term durability rested with improvements to the assembly. After looking at different solutions, they landed on converting it to a new clock-spring construction. The clock-spring features a conductive ribbon made of nickel that’s wound around a tensioned spool. As the float arm swings in one direction, the nickel ribbon unwinds. When it swings in the other, it contracts all while maintaining steady contact with the sensor card.

The clock spring’s sturdier design:

  • Reduces the number of contacts against the sensor card, thereby minimizing the potential for long-term wear and tear.

  • Eliminates the need for the ground plane, which reduces costs.

  • Cuts precious metal content in the wiper and the card by 50 percent and 65 percent, respectively, thereby setting new cost benchmarks for the module.


Internal view of fuel delivery module wiper assembly with redesigned clock spring
We also redesigned the wiper assembly to feature a clock-spring, which minimizes long-term wear and tear.

Bringing it all together to help vehicles go further.



Looking ahead.

As the fuel management landscape continues to shift, we’re actively seeking solutions to the challenges you face, including increases in on-fuel module content and functionality, as well as improved cylinder deactivation and hybrid system performance. Check back for updates on our progress.