How To Check Fuel Pressure Without Gauge?

What’s the first thing you think when a car refuses to start? A dead battery or a swear. However, before panicking and running off to replace your battery, you may need to consider checking your car’s fuel pressure.

Many times, when your car experiences a tricky start, it may be due to low or no fuel pressure. This means the pressure pump is not working well, and sufficient pressure is not reaching the engine from the fuel tank. A malfunctioning pump can cause the engine to hesitate from starting up or resist when the car accelerates.

Professional mechanics use a fuel pressure gauge to check a car’s fuel pressure. Owning one ourselves is an ideal scenario, though. Most of us don’t have easy access to a fuel pressure gauge. The good news is you can still check fuel pressure without the gauge. Just follow one of these three simple methods, and you will have solved all your low fuel pressure worries instantly.

Moreover, you will be able to detect your fuel pressure regulator issues independently, without professional help or equipment. So what you need to do is either use a diagnostic code reader, check for the buzz of the engine upon turning on, or check the fuel pump and pipes manually.

Use of Diagnostic Code Reader

Known as the OBD ii Scanner, this tool provides live fuel pressure data. However, this can only be used for newer cars manufactured in 1996 and later. As opposed to older fuel-injected engines, newer cars are built with a fuel system that has fuel pressure sensors. These sensors monitor the actual fuel pressure coming from the fuel injectors. In case of lower fuel pressure, this can be scanned by the diagnostic scanner.

Use Of Diagnostic Code Reader

The compatibility of these protocols has to be checked before checking the fuel pressure without a gauge.

These diagnostic scanners do not give actual numbers readings of the fuel rail pressure. However, they have inbuilt diagnostic trouble codes which can tell us whether our vehicle’s hard start-up is due to low or high fuel pressure. Hence the OBD ii scanners are helpful tools to measure your car’s fuel pressure without a gauge.

Method

To check fuel pressure using the diagnostic code reader, first of all, start your engine and leave it idle for a couple of minutes. This is to warm up the engine and get idle fuel pressure. Cold engines can give false fuel pressure readings.

Next, connect the scanner to the OBD ii port of your car. In case you have trouble locating the port, check your owner manual. Usually, the port is located under the steering wheel, right above the pedals. Using a universal scanner, use the OBD ii pin found in the car’s engine bay.

There are stored OBD ii error codes in the scanner. If there is a problem with the fuel transmission, the reader will display one or more error codes. These will be in the P series, such as POO 87, PO18C, PO191, etc.

Different codes signify a separate issue. For instance, POO87 means the fuel system pressure at the sensor is too low. PO18C will display ‘fuel pressure sensor B circuit low,’ which means there may be a fault with the sensor itself. PO191 will display ‘fuel rail pressure sensor circuit A.’ This means there is a malfunction in the fuel rail pressure readings. This is caused due to electrical or mechanical issues such as low or higher pressure.

If the stored OBD ii error codes do not display any issue that involves fuel pressure, check the live fuel pressure data on the scanner. Observe it for a while. However, all diagnostic scanners don’t have this monitoring feature, so you may need to check the scanner’s compatibility first.

Additionally, if your scanner has a real-time data feature you can monitor the live fuel pressure data. To do this, connect the scanner and enter the engine DME diagnostic mode with the current fuel pressure readings. Once you do so, choose the ‘fuel delivery system’ option. This option will show you the maximum fuel pressure on the rail when the engine is running. Compare this reading with the live fuel pressure reading. If both readings are similar, it means all is ok, and there is no problem with the fuel delivery. Otherwise, there may be an issue with the fuel delivery system.

Fuel Pump Buzz

What if you don’t have a fuel gauge and you don’t have a diagnostic scanner, but you still need to check the engine’s fuel pressure. No worries, as you can employ this basic method and still get an idea about your car’s fuel pressure regulator. All you need is a sharp sense of hearing to detect the buzz of your car engine.

Fuel Pump Buzz

Method

For this procedure, turn on the key of your car to switch on its fuel pump. Now carefully listen for a buzzing sound that the pump makes. If you hear the buzz, your fuel pump is functioning well.

The buzzing is the sound the vehicle engine makes when it is getting ready to function. The car buzzes when the pump exerts liquid pressure on the fuel pipes, which lead to the fuel injectors.

In case you do not hear the buzz, it means there may be low fuel pump pressure. It could be due to various issues in the car’s fuel pressure and injection system. Perhaps a relay switch or one of the wires is broken, there is a blown fuse, or worse still, the fuel pump needs replacement. Hence, if faced with such a situation, you need to get professional help from a mechanic.

Manually Checking Fuel Pump and Pipelines

So you have checked for the buzz of the pump, and it’s all buzzing and well. However, your engine may still not be performing correctly. It may be experiencing hard starts and stalling now and then. In that case, it is a good idea to check the pump the good ‘ol manual way, using your fingers and good working knowledge about your car’s anatomy.

Manually Checking Fuel Pump And Pipelines

Checking Fuel Pump

You need to remove the fuel pump from its position for this method. Locate it under the backseat of your car, and take it out. An OUTPUT port is located on the pump, which has a hose connecting the pump to the fuel filter. Take the hose out, and place your finger against the opening tightly. Now turn on your car’s engine, with your finger in place on the hose opening. If you feel the fuel giving your finger a good thrust, it means the fuel pressure is acceptable. If not, it is time to replace the faulty fuel pump.

Checking Filter and Fuel Pipes

Remember that your car’s fuel network system is like any other mechanical system comprising of different parts and passageways dependent on each other for smooth functioning. If you are experiencing low fuel pressure, the fault doesn’t necessarily lie with the pump.

Conclusion

Optimum fuel pressure is integral to smooth engine performance. For this, you need to monitor the fuel pressure of your car continuously and have routine maintenance. If you don’t ensure correct fuel pressure, you may be landing yourself in car troubles when you least expect them.

Having workable knowledge about fuel pressure set points is a wise idea. For this, some of the simple methods we mentioned above that work well with all diesel engines are valuable tools to detect your vehicle’s fuel delivery rate. Follow steps like using a diagnostic code reader, hearing for the buzz of the fuel pump, or giving a manual check to the different parts of the fuel pressure system for checking fuel pressure without a gauge.

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