If you have difficulty accelerating, especially on the highway, or see other signs that could indicate that your car is not getting enough fuel, there may be a partial blockage or obstruction in the fuel line, fuel filter, pump or injector. If the car won't start at all, there are some quick tests you can do to determine whether or not it's what's causing the problem.
Method 1 of 2: Perform an Electricity Test
Step 1. Check the fuel pump fuse
Often the problem with operation is not with the pump itself, but with the electricity that powers it. Read the user manual to find the fuse box. Next, find the fuse for the fuel pump. Take it off and check it for signs of failure. If the fuse is blown, it will be broken or blown. If it looks good, check the rest of the fuses related to the fuel system for signs of a blown fuse and replace it, if necessary. If the fuses are not blown, have someone turn the key while you hear the fuel pump relay click.
- In the event that you need to replace the fuse, be sure to use one with the correct amperage, and never install one with more amperes than necessary.
- If you find a blown fuse, it could be a sign of high amp draw and that you need to check individual circuits. Replace the blown fuse and try to start the vehicle. If the fuse blows again, there is a direct short and a diagnosis is required. Take your car to the shop to have it examined.
Step 2. Check the pump voltage
Just because power is being drawn from the circuit does not mean it is reaching the pump itself, so it is important to check the voltage as well. Read your vehicle manual for where to check and the correct procedure to do so.
Tests the source voltage to determine if the charge coming out of the fuse reaches the pump. If it doesn't come, check the pump relay circuit. There may be a faulty relay
Step 3. Do a drop test with a voltmeter
Check if the power cord is full voltage and the ground wire is properly grounded. If the electrical test reveals nothing, the problem is probably the fuel pump and you need to replace it, although you can further verify this through an additional pressure test.
If you see a difference of more than one volt, it means there are problems with corroded wires or with the circuit on the positive or negative side. Take the car to a workshop for tests and advice
Method 2 of 2: Perform a Fuel Pressure Test
Step 1. Eliminate the filter as a possibility
If the filter is clogged with sediment, you may have trouble accelerating and suspect that the fuel pump has a problem. To check, remove the filter and drain excess fuel. Use a short piece of rubber hose at the inlet of the filter. Blow through the filter inlet and pay attention to resistance, which should be minimal. Inspect the screen for dirt and replace the filter if necessary. To do this, blow through the outlet and collect the debris with a white cloth or towel.
Step 2. Get a fuel pressure gauge
Commonly available at most auto parts stores for an inexpensive price, a fuel pressure gauge is a good investment, useful for most car makes and models. If you don't want to buy one, you can borrow it from repair shops or auto parts stores that offer this possibility. The test only takes a few minutes.
Step 3. Attach the gauge to the fuel pump test fixture
Find the test point on the pump, which is usually near the injector, and find the point where it fits into the filter's fuel relay housing. There should be a separate small gasket or test port where the indicator connects.
Different devices may have slightly different instructions, and the location of the fuel pump varies by vehicle, so read the owner's manual for more precise information
Step 4. Have one person run the engine while you check the pressure
Allow the vehicle to warm up a bit. Then check the pressure at idle speed and the rated speed indicated in the pump specifications. If you don't know the rated speed, run the motor and observe the pressure reaction. If you have a serious problem, the needle will not move or will be well below specification, indicating that the pump needs a replacement.
The pressure should be as indicated in the repair manual, and should increase proportionally as you accelerate. If it doesn't, you will need to change the pump and filter
- If the fuel pump needs a replacement, a rebuilt one is usually just as good as a new one, and much cheaper. If you're brave, some manufacturers offer rebuild kits. You can disassemble the pump with a screwdriver and put it back together, following the instructions in the kit. If the idea doesn't seem interesting, ask the auto service to locate and install a rebuilt pump, which should be warranted for at least three months.
- Precautions must be taken to perform tests and diagnoses safely. Keep a fire extinguisher nearby while you work or test the fuel system.