When you own a car, then checking the automotive fuel pressure is an important part of your regular car maintenance schedule. Your car’s fuel pump is the part that works to supply gas to the car engine’s fuel injectors. This process remains the same with both gasoline and diesel operated cars. So, any defect or issue in this pumping system can cause the fuel pressure to change. Measuring the fuel pressure accurately is extremely important as it helps to check whether your engine performance is optimum or not.
A faulty fuel pressure reading could point to various problems with the car which if left unchecked could lead to big troubles while you are on road. In fact, if you get stuck on the road then also checking the fuel pressure is one of the primary steps that you need to execute.
Why is it Necessary to Check the Fuel Pressure
Maintaining the correct pressure in the fuel pump is an important aspect of maintaining a good car engine health. The fuel system design varies from car to car and hence there can be one or more models of pumps in both electrical or mechanical models.
The direct injection fuel system is compatible with both gasoline and diesel models of cars. It consists of a primary pump in the fuel tank and a secondary pump of high pressure which mounts the engine and is driven by it.
A regular pressure fuel injection system consists of one main pump in the fuel tank.
Over a period of time, the internal parts of the car fuel pump begins to develop flaws and issues due to regular wear and tear. The loss of fuel pressure causes problems in the fuel injections and this leads to complications like low engine power, hesitation, or hard starting. It can grow worse gradually leading to the point when the engine will not even start.
Types of fuel systems
Usually, there are two types of fuel systems available in the market.
The first type of fuel system comes with a fuel return line which leads back to the fuel tank. It also comes with a fuel pressure regulator located on the fuel rail that contains a return line to the fuel tank.
The second type of fuel system is called returnless fuel system as it does not have the return line leading back. This type does not have a fuel pressure regulator on the fuel rail.
A fuel pump control unit or a fuel pump driver module is used by some returnless fuel systems. The fuel pump driver module sends out a pulse width modulated signal to the fuel pump. The engine computer is also used to control the fuel pump which in turn controls the fuel pressure. The higher the pulse width modulated signal; the higher will be the fuel pressure.
When you are checking the fuel pressure it is very important to know which type of fuel system you are working with. The correct specifications are vital for you to measure the fuel pressure accurately.
Checking Fuel Pressure
Checking the fuel pressure is a very important step if you wish to ensure good car health and proper functioning of your car engine. You will need a special equipment called a fuel pressure gauge to measure the fuel pressure accurately.
Depending on the system it can take you a few seconds to a few minutes to hook in a fuel pressure gauge properly into the vehicle. Usually, most systems come with a pressure test port where you can screw the gauge right into the fuel rail to take reading. But in the absence of such a port, you have to tap in between the fuel line. At first, you have to remove the fuel line from the filter or from the fuel rail and install the fuel pressure gauge in between the two so that you can take the reading.
Some fuel systems are designed to be at 30 PSI to 40 PSI whereas in other systems the fuel pressure might range from 50 PSI to 60 PSI. You have to check the specifications well before you decide whether the fuel pressure is in the correct range or not.
What kind of Tool or Equipment will I Need
In order to check the fuel pressure only, you would need a fuel pressure gauge that you have to screw in and take the pressure reading. There are various types of fuel pressure gauges available in the market and you will not have any problem to choose one for yourself.
If you wish to get a kit or an equipment to ascertain whether something is wrong with the fuel pressure, fuel pump, fuel line, or something else then a complete fuel pressure kit will be the ideal tool for you. These are not exactly cheap but they perform a whole range of functions so getting a complete kit will be an empowering decision. It is well suited for you if you are a DIY enthusiast.
Stepwise Instructions to check the Fuel Pressure
Say you are stuck on the road and your car refuses to accelerate properly. Or, you can sense that your car is struggling to get sufficient gas to run well. You know these are the classical signs of a blockage in the fuel line, fuel pump, fuel filter, or injector. Do not feel agitated. Jump in and begin your DIY routine to locate the problem.
- Examine the fuel pump fuse
Pull out the fuse of the fuel pump and check it well. If it looks broken or burnt then you would have to replace it right away. If this fuse looks fine then check all the other fuses.
Replace the blown fuse with a fuse of correct rating. However, if the fuse blows again when you start the car you have to get the circuits examined for a probable short circuit.
- Examine the fuel pump voltage
Sometimes it is the source voltage that is causing the problem. Test it and make sure that power is making to the fuel pump.
- Examine the fuel filter
The problem may not be in the fuel pump but in the fuel filter. Check the fuel filter for possible clogging. Remove the filter, drain away the excess fuel, and remove the accumulated debris. Blow through the filter and see if it is working fine.
- Examine the fuel pressure
Always keep a fuel pressure gauge with yourself. These are handy tools and do not cost too much. The first thing to do would be to find the pump test point that remains close to the fuel injector and to find the point where the pump will attach with the filter injector rail. Next, you have to find the test port where the fuel pressure gauge would attach itself. This step varies a bit with different models.
Once the pressure gauge has been attached, ask someone to rev the engine. When the engine warms up, you have to take the pressure reading at idle speed and also at rated speed. If the pressure does not match with the specifications mentioned in the manual, the fuel pump has a problem. It should also increase when you rev the engine. If these things do not happen then it would be a sign for you to replace the fuel pump and also the filter.
When you are doing a fuel pressure checking, keep a fire extinguisher tool handy. Sometimes accidents may occur and you would want to be ready to deal with that. Always take proper precautions and safety measures when you are working on a car.
If you find out that you have to replace your fuel pump then you can go for a rebuilt one instead of investing on a brand new one. A rebuilt one costs less and performs as well as a new one. You can actually rebuild a set yourself but if that sounds like too much trouble then you can buy one assembled by a manufacturer.
- If the engine backfires a few times, turns over but refuses to start, what could be the problem?
It might indicate a couple of problems. Check if the ignition coil is unplugged or has gone bad. The fuel filter could be ruined as well. You should also check out the fuel pump to ensure that it is functional.
- How to pressure test a fuel pump?
Take the fuel pressure gauge and attach it to the test port. Then you have to cycle the key on and off a couple of times. Now the pressure reading should go up and point to the values given in the specifications. It should not drop for around 10 minutes and even if it does, it should not drop by more than 1 PSI or 2 PSI.
- How to check fuel tank capacity?
You can check the user manual or refer to the online manual if you have lost the booklet. If you find nothing then you can drive on till the fuel warning light turns on. Fill your tank at this point and note how much you filled.
- What is the ideal value for fuel pressure?
There is no ideal value for fuel pressure and it depends on the type of vehicle you own. It usually ranges from 30 PSI to 60 PSI based on the model of the car you are driving.
- What happens if the car cranks but does not start?
Do not keep cranking the car as it might damage the starter or the battery. Then check the fuses, fuel pump, spark plugs, relay switch, fuel filter or coil packs. Usually, there is a problem with any of these parts.
Checking the fuel pressure of your vehicle is pretty simple if you have the fuel pressure gauge with yourself. It is one tool that can help you to detect probable issues in your car and get them fixed properly. Once you have the proper equipment and the necessary know-how, it will be so much easier for you to locate the issue with your car and to attend to it yourself.