How to check Fuel Pressure

Checking fuel pressure is very vital in diagnosing an engine performance issue. Depending on the application, it will take any where from a few moments to a few minutes to hook up a fuel pressure gauge. Most systems you can screw right into the fuel rail at the pressure test port while others you will have to tap into the line by removing the fuel line from the rail or even the line from the filter and installing a fuel pressure gauge in between the two in order to get an accurate reading.

Checking Fuel Pressure

Some fuel systems are only at 30 to 40 psi while others range in the 50 to 60 psi range or more. Once you know what your fuel pressure is at, you are going to want to go and look up the correct specifications for your vehicle to see if your fuel pressure falls within the factory specs. You can go to ALLDATAdiy or another source to look up your specifications for your vehicle. If the pressure is low you will need to be sure that the filter and the high pressure line is not pinched or plugged up in any way. In addition, be sure that the pump has full battery voltage and a good ground before you replace it.

Here are a few pictures of me checking fuel pressure on a 1997 Chevy truck 1500 with a 5.7 liter engine.  The fuel pressure test port is on the fuel rail on the drivers side of the engine.  It simply screws right in and you can take a fuel pressure reading.

fuel pressure test port

And here is the fuel pressure reading after turning the key on and priming the system.

fuel pressure gauge

Which Fuel Pressure Tester should I use?

There are several different type of fuel pressure testers. If you want a good quality fuel pressure test kit that will do just about everything and will last for a life time, I would recommend to go with an OTC or a Snap On fuel pressure master kit. OTC Master Fuel Injection Kit will work just fine and you will save 200 bucks compared to the Snap on master fuel pressure kit.

A cheaper alternative would be one of the Actron fuel pressure gauges. They seem to be accurate, but they have their quirks. The seals and o rings need to be replaced regularly in order to prevent them from leaking fuel. So just careful. The good news is that it is cheap and easy to use. The Actron Fuel Pressure Tester is a good choice as it comes with the basic adapters. You can pick this up for about 44 bucks.

Checking Fuel Pump current

Another good way to check to see if your fuel pump is bad is to check to see how much current your pump is pulling. You would measure current in Amps. You will need either a voltmeter that has an amp setting or a voltmeter that works with an amp clamp or a lab scope. I like using a Fluke 87with an amp clamp for this job. It is a fantastic and extremely reliable voltmeter. Just clamp around the power wire going to the pump itself and start the vehicle. On some vehicles, you can remove the fuel pump relay and jumper the hot wire going to the relay and the pump should run. The amount of amps/current your pump will pull will depend on how much pressure your fuel pump should supply to the rail. A good rule of rule of thumb for this test is as follows: 14 to 15 psi 3 to 4 amps, 30 to 45 psi 4 to 7 amps, 45 to 50 psi 7 to 8 amps, 50 to 70 psi 8 to 12 amps.

How to check fuel pressure