How to Check How Much Gas You Have With a Broken Fuel Gauge

How to Check How Much Gas You Have With a Broken Fuel Gauge

The fuel gauge is one of those essential car components you really need working correctly, or you may very well end up stranded in the middle of the road with an empty gas tank.

Fortunately, there are a few ways to determine your car’s fuel level if you find that your fuel gauge is reading incorrectly. Here is how to check how much gas you have with a broken fuel gauge.

Fuel Gauge Not Working? How to Check How Much Gas You Have With a Broken Fuel Gauge

If you have a broken gas gauge, it can be difficult to keep an eye on your car’s gas levels while driving. Here is how to check your car’s fuel levels if your fuel gauge is not working.

Step 1

Start by reviewing your car manual to find out the fuel capacity of your tank. Larger vehicles can hold up to 20 gallons while smaller ones typically fill up to 15 gallons.

You should also look up the model specifications of your car to determine its gas mileage. Most cars usually have 350 to 400 miles per gas tank.

Step 2

Fill up your gas tank and start driving as you observe the odometer. This is to find out how far you can drive with a full tank.

Insert a liquid dipstick into your gas tank and then pull it out to check the level of fuel in the tank.

The stick will show you how much fuel is left in your gas tank. Refill after about 300 miles so you don’t run out of gas while on the road.

Why Is My Fuel Gauge Not Working (Properly)?

A fuel gauge has two main parts: the sending unit in the gas tank and the indicator located on your dashboard.

In most cases, the sending unit is usually the culprit when it comes to faulty fuel gauges, but issues can also arise from corroded wiring, blown fuses, or simply a bad gauge.

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1. Compromised sending unit

A malfunctioned sending unit is the most common cause of broken fuel gauges. There is a lot of motion inside this unit, which can cause components to get corroded, worn, or disconnected.

The resister and wiper, in particular, are always rubbing together. Overtime, they may wear out so that the sending unit is unable to send the correct signal, causing the fuel readings to appear either empty or unchanged.

If your fuel gauge reads empty even when you have gas, it’s probably because the float has physically separated from the wiper.

Sometimes an old wiper can get stuck on the resistor and then get jostled back into place when you hit a bump or pass a rough terrain. When this happens, you will notice some strange fluctuations on your fuel gauge display.

2. Circuit issues

A broken fuel gauge can also be caused by an issue with your wiring. If your wiring has a problem, it will be rather impossible to send signals to the fuel gauge.

Wiring problems can be linked to the battery, the sending unit, or the wires in between and typically occur when the cables corrode or break due to wear.

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3. Bad gas gauge or instrument cluster

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Depending on your car, the fuel gauge can come independently or as part of the instrument cluster.

In both cases, a problem with the fuel gauge can occur if the internal circuits are jeopardized so that they are not able to transmit signals properly or even at all.  

If the issue is small such as a blown fuse in the gas gauge or instrument cluster, you can easily replace it with another one.

However, if it’s the whole instrument cluster that needs to be replaced, you may have to cough up some money.

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Fuel Gauge Reading Empty When Tank Is Full: What Should I Do?

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It is common for a faulty gauge to read empty when the tank is full or empty when there is fuel in the tank. If you are dealing with this problem, here are detailed steps on how to diagnose your fuel gauge:

1.  Check if all your wiring connections (on the sending unit and fuel gauge) are clean, secure, and free of debris and corrosion. Now turn the ignition on and off and see if the needle moves. If it does, your gauge is working.

If it doesn’t, check to make sure you don’t have a blown fuse on the fuel system. Read your service manual if you are not sure where to locate these parts.

2. Connect the jumper wire to the ignition switch and the terminal at the back of your gas gauge and then start the car.

If the needle on the gauge moves, it means that there is a problem with the wiring between the ignition switch and gauge, so you need to do some replacement.

3. Get a good wire and connect it to the chassis ground and ground post of your sending unit. If the gauge needle moves when you turn on the vehicle, then all you have to do is replace the ground wire.

4. Take one end of the jumper wire and then clip or solder it onto the outside of your fuel tank. This is to ground the sending unit. If the gauge starts to work now, replace the grounding wire of your sending unit.

5. Disconnect the wire leading from the sending unit to the fuel gauge, and then turn on the engine. If the fuel gauge shows that the tank is full, you have a faulty in-tank mechanism or sending unit.

If the fuel gauge reading empty when tank is full, the fuel gauge is probably broken and needs to be replaced.

Generally, most components in your car that use electricity will not function properly if you have a bad fuse.

As such, this is where you should always start when diagnosing an automotive problem, especially if the problem is connected with the dashboard.

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FAQs on Faulty Fuel Gauge

Is it illegal to drive with a broken fuel gauge?

It is not illegal to drive with a broken fuel gauge. However, any careless or dangerous driving that results from running out of fuel due to a faulty fuel gauge could land you in trouble with the law.

How far can I drive on an empty tank?

Generally, most cars have a reserve of about 2.5 gallons in the tank when the gas light turns on. This can take you up to 30 to 60 miles, depending on the miles per gallon you get with your vehicle.

How much does it cost to fix a broken fuel gauge?

If it is the gas gauge itself that is broken, you can find a cheap replacement starting from $50 to $200 depending on the make and model of your vehicle. Of course, you also have to add labor cost if you are having it professionally replaced.

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Hopefully now you know how to check how much gas you have with a broken fuel gauge. An accurate fuel gauge should drop steadily depending on the speed and distance, after a fill-up.

If your fuel gauge shows a full tank after driving 90 miles, or reads empty after just refilling the tank, you may have a fuel gauge problem.

It is advisable to avoid taking long trips until you have your gauge fixed or replaced, and always err on the side of caution when refilling the gas tank.

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