How do you detect a fuel pump problem? What happens if the fuel pumps fail? Tests for fuel pump measurements, fault detection and control methods
The engine won’t run properly if the fuel pump doesn’t send enough fuel and pressure. Low fuel pressure can cause the vehicle to misfire, misfire, idle, misfire or stall.
Injection engines are sensitive to fuel volume and fuel pressure. The engine may run well if the pump can supply enough pressure but not enough gasoline. It can also cause engine power loss due to sudden accelerations or severe conditions.
“Engine Doesn’t Run, But It Cranks”
The engine will not start if there is a problem with the fuel pump. However, the engine may not start due to a problem in its ignition system. (Like a worn timing belt).
Attention: When cranking, do not touch the spark plug wires!
You can test the ignition coils by removing them and testing for problems. The ECU uses ignition coils to spark the spark plug in the next cylinder. To ensure sparks are reaching the engine block, inspect the wire connectors, sparkplugs and coils. You will see sparks in your engine block if the ignition system works properly. If there is no spark, it could be a problem with your crankshaft position sensor or ignition module.
To check if the engine’s compression system is failing, timing and “V” belt checks are recommended. The crankshaft can turn badly when worn, damaged, or loose belts are present. This makes the crankshaft uncontrollable and can cause compression problems.
Attention: When starting, keep your fingers clear of belts and gears!
The most common reason your engine won’t start is fuel shortage. Is your fuel pump defective?
Fuel Problems
1- A defective fuel pump (Pump or pump relay, pump fuse), a fault within the wiring circuit
2- Fuel filter clogged
3- Low fuel pressure (Weak pump or crushed fuel pipe, low voltage regulator, or fuel pressure regulator).
If the engine is not running but the pump is still running, it is possible that the engine pressure is normal.
1- The fuel injectors are not powered by electricity (Injector fuse, defective relay).
2- Communication problem between ECUs and injectors (Cables, or software related problems).
3- Short circuit in injectors
Fuel Pump Controls
You should first check that the pump is making a noise when you turn on the ignition. If the pump does not make a sound, it is probably not working.
Most vehicles have an ECU that sends electricity through a relay to the pump. When the ignition switch has been turned on, the ECU sends current via a relay to fuel pump relay. The pump then runs for a few minutes until pressure builds up. The fuel pump relay will be shut off if the ECU doesn’t receive a rev signal to indicate that the engine is running. The fuel pump has relays that shut off fuel flow in the event of a pressure drop or accident.
The fuel pump will not start if the relay is defective. You will find the fuel pump relay inside the engine compartment. It is usually located near the electrical centre. Turn off the relay and give it a good shake. The relay may be defective if it wobbles when you shake it.
Turn off the relay to test the fuel pump. The relay will then send power directly at the fuel pump. It is important to have enough knowledge about the relay to be able disable it. You could cause more serious malfunctions. To check the situation, an auto electrician will have a test relay. This relay can be deactivated by turning on the on/off switch. The relay may be defective if the pump is not running. The relay could be defective or disconnected from the pump.
Checking the Fuel Pump Pressure
The fuel pump should be able to build up fuel pressure between 30 and 80 psi depending on driving conditions. Injection engines are sensitive and sensitive to fuel pressure. Even if fuel pressure drops by 1-2psi, an engine might not start or stall.
Depending on the vehicle’s model and fuel injection system used, as well as the vehicle’s performance and emissions requirements, pressure characteristics can vary. To solve fuel-related issues, it is important to understand the vehicle’s pressure characteristics.
High fuel pressure causes the engine to run rough. This leads to an increase in fuel usage and carbon monoxide emissions. This makes the engine run more efficiently. Spark plugs can become carbon and soot deposits, which can cause fluctuations at idle.
The engine won’t start if there isn’t enough fuel pressure. The engine will become lean due to the formation of a mixture. This can cause misfires, fluctuations, shaking, and power loss at idle.
A gauge and a location to mount it are necessary for checking fuel pressure. The engine should be turned on, off, and running. There are several ways to test this. You can test the fuel pressure regulator or injectors separately.
Different manufacturers have different testing procedures. It is recommended that you perform a static pressure test on many European EFI systems. This requires the ignition and engine to be turned off. This can be done by bypassing your fuel pump relay and directly energizing your pump. Asian vehicle manufacturers attach a tester piece to the fuel relay to perform the pressure testing while the engine is running.
A pressure gauge must also be installed in the fuelline, just before the injector fuel rail, if the vehicle does not have pressure testing capabilities.
Attention: Before the pressure gauge can install, all pressure must be released from the fuel system.
Static Pressure
The ignition is switched on, but the engine has not been started. (Fuel pump start). The fuel pressure increases rapidly, and then reaches a constant level. Compare the pressure value with the vehicle’s specifications. If the pressure is not rising, you should check that the pump has power. You have identified the problem if the pump won’t start, even though it has voltage. You have a problem with the fuel pump.
Low pressure can be caused by a weak pump or clogged fuel lines, dirt in the tank or fuel filter, or a malfunctioning pressure regulator. A low voltage could also cause normal pressure to build up. It is important to check the voltage of your pump.
Idle fuel pressure test
Compare the readings of the gauge and the specifications of the engine while the engine is running. The manufacturer should allow for fuel pressure to be within the allowed range. Low fuel pressure could indicate a problem with the pump, low voltage or fuel filter.
Fuel Density Testing
Driving problems can result from a normal pressure fuel-pump that is not able to deliver sufficient fuel density to the engine. This is why the fuel density testing is the best way for you to assess the pump’s condition.
The fuel density test measures how dense fuel is delivered within a specified range. The fuel density test is performed by connecting a fuel flowmeter to the fuel supply and disengaging the fuel return from the regulator. The regulator must be connected to a large container.
Caution: This test should be performed with caution.
Turn off the engine and start the pump. Measure the fuel flow at the indicated interval. A good pump should deliver approximately 3/4 to 1 Liter of fuel in 30 seconds.
Low fuel delivery could be caused by a weak fuel pump or a clogged filter. A tank that is clogged with debris and rust, a clogged line, or an empty tank. The pump’s voltage may be too low to allow it to run fast enough to produce sufficient fuel flow. The pump should have a supply voltage equal to half the system voltage. If the voltage is low, you should check the wiring, relay, or ground.
Test for the Fuel Pressure Regulator
This test is to verify the operation of regulators, which adjust the fuel pressure in response o air changes in the engine. This is essential to ensure that the injectors receive the correct fuel and keep the engine running smoothly.
While the engine is running, disconnect vacuum hose and pressure regulator. When the vacuum hose is disconnected, the fuel system pressure should be between 8-10 psi. Any change in pressure will be a sign of a faulty pressure regulator and a clogged or leaky vacuum line.
If the regulator is not connected to the vacuumhose, you should also check for any moisture. The regulator diaphragm may be leaking if the hose’s interior is damp. This can cause a drop in fuel pressure. This is caused by fuel leaking into the intake manifold, spoiling the mixture of air and fuel. Replace the regulator if the diaphragm leaks.
