Peculiar Fuel Pump Problems and How to Detect Them

Fuel Pump Problems
Though rare, fuel pump problems cannot be ruled out, and thus, being aware of these problems and the methods of diagnosing them can be of great help.
One of the most vital components of your vehicle, the fuel pump is a device used to pump fuel from the fuel tank to the engine or fuel injection system. There are basically two types of fuel pumps – (i) mechanical and (ii) electric. Most of the vehicles in production today come with an electric pump. In fact, in some of these models, the pump is located inside the fuel tank. Irrespective of which of these two types of fuel pump is used in your vehicle, problems with the same cannot be ruled out.

Fuel Pump Problems: An Overview

Fuel pump problems, such as inadequate pressure or a malfunctioned equipment, are often traced to poor maintenance or handling of the vehicle. The risk involved is maximum if you are guilty of using the vehicle in spite of low fuel, or using contaminated fuel for that matter. Inadequate pressure will either prevent the car from starting, or cause the engine to start and quit while running. If the pressure is normal, but volume is inadequate, the engine will work, but other problems, like power and inadequate supply of fuel to the engine, may arise. In case of bad fuel pump, however, the engine will not start at all.

In modern vehicles, the electric fuel pump is programmed to stop functioning in the event of an impact. This is done to prevent fuel leakage and further damage in case of accident, i.e., if the car collides with something or rolls over. In cases like these, car owners misdiagnose the problem and opt for the replacement of fuel pumps. Though the fuel pump in itself is not very expensive, service charges definitely are. And therefore, it is wise to ensure that the problem lies with the fuel pump before you opt to get it changed.

Symptoms and Diagnosis

Symptoms of a bad fuel pump, such as engine refusing to start, misfiring, or stalling, can give you a rough idea about the problem on the basis of which you can go for a proper diagnosis. The diagnosis includes a series of tests measuring fuel pump pressure. The test procedures may differ from one car make to another. In order to check the pressure, you will require a gage. You can use it to perform any of the few simple tests discussed below. (Most of the vehicles in production feature a pressure test fitting. If your vehicle doesn't, you can use a tee to connect the pressure gage to the fuel line.)

Dead Head Pressure Test: Check the maximum output pressure of the fuel pump. Ideally, it should produce twice the normal operating pressure at idle. If it doesn't, it is an indication of a bad fuel pump.

Fuel Pressure Drop Test: Measure the drop in static system fuel pressure by energizing each injector with an injection pulse tester. The difference in readings of all injectors should be 2 psi or less. If it is more, it means there is some problem with the mechanism.

Fuel Pressure Regulator Test: Analyze the operation of the fuel pressure regulator to check whether the regulator changes the line pressure when the engine vacuum changes. If it doesn't, it means the fuel system is not working properly.

Residual Fuel Pressure Test: Analyze the residual pressure for a few minutes with the engine turned off. If the pressure drops quickly, it means the fuel pump is not working to its capacity.

Running Fuel Pressure Test: Take the reading when the engine is in idle mode and compare it with the specifications provided by the manufacturer. Low readings typically suggest a problem with the mechanism.

Static Fuel Pressure Test: In this test, you monitor the fuel pressure with the key on and engine off. In normal condition, the pressure should rise quickly and become steady at a particular value. In case of bad fuel pump, you will see the voltage, but the pump won't work.

At times, an underlying problem with the ignition system or compression can also cause the engine to crank and go down. So, it's better to check whether all the other things are in place, before jumping to the conclusion that the engine is not starting because of bad fuel pump. After all, the task of replacing a fuel pump is a tedious job, which calls for professional expertise, and that is likely to blow a hole in your wallet.