Fuel Pressure Test

I had once read about Mercedes somewhere - the humorous take on Mercedes goes like this - a model of Mercedes is being tested by a customer. After a good run, it abruptly stops. The customer, on asking about it, gets answer - "Sir, do you know how this car went even this distance?" Customer says no. The showroom manager says, "It ran on the goodwill of the brand name, sans fuel!" On a serious note though, fuel and the fuel system of a car, just like a digestive system of a body, is extremely crucial for the proper functioning of the car. A lot of how a car runs depends on the fuel pressure and the whole fueling system. It then, becomes mandatory to check the pressure periodically.

How to Test Fuel Pressure?

To check the pressure in a car, you need a pressure gauge and tester. You will also need adapters for your vehicle. Poorly running car can be a result of inadequate fuel pressure. Fuel pump replacement will have to be considered in case the pump has completely broken down.

Step 1
Once you have gathered the tester and the other supplies required, you have to find the fuel pressure port. For that you may have to check the manual. It is also possible that you may have to T-into the fuel line.

Step 2
Turn the car ignition on and jot down the reading. After that start the car and record the readings after running it.

Step 3
There is a possibility that the problem in the car can occur while you are driving it. In that case, you may have to take a road test for keeping a record of the fuel pressure when the car is in motion.

Step 4
Tape the gauge to the windshield and have someone check the pressure, while you drive. Compare the readings with the ones corresponding to your car in the manual.

Step 5
On testing fuel pressure, if the pressure is matching the specifications of the car, then no worries. If it is not, then you will either have to change the fuel filter or need to take a look at it again.

In addition to these, see for the symptoms of a bad pressure regulator. What you need to do is unscrew the pressure gauge from where the fuel will come out and then hook the tester in it.

What next? What do the readings indicate? What impact does it have on parts like spark plugs? Well, here are the answers !

Fuel Pressure Scenarios

A low down on the most likely scenarios after you have found the pressure. A very important one is about the pressure regulator.

More Fuel Pressure than Required
Just as low pressure is not a good indication, more pressure too, is not good. What will happen in that case is, extra pressure will force more fuel than needed through the fuel injectors. This will lead the engine to run rich and that in turn, will cause harm to the spark plugs, black smoke and surging or sluggish idle. Fuel pressure regulator will have to be checked for problems in that case.

Low Fuel Pressure
If, after the test, low pressure is found out, that may be the answer to your car not performing up to the mark. Poor engine output, choppy idle and a misfire can be a result of low pressure. It can also mean that the fuel filter is clogged. Hence, before you go for the fuel pump replacement, be sure. Sometimes, replacing the fuel filter will do the trick.

Finally, before you conduct the test, make sure that the fuel pump is running. Hear closely for a distinct sound emitted by the fuel pump. Make sure that there is no bent, twisted or pinched fuel lines. Also, see if you can do the fuel pump relay test. If the fuel pump does not work, replacement could be on the cards. In case, this seems to complicated, you can always go to a mechanic and get the test done. I am sure you will get a clear picture.