How to check your fuel pressure

Checking your fuel pressure is something that is easy to do yourself.  If you took your vehicle to a garage to have the fuel pressure checked you would probably pay $50-$100 but you can do it in your driveway for free!  Many local auto parts chains will rent specialty tools, like the fuel pressure gauge we used in this video, and give you your money back when you return the tool.

Before we elaborate on the how, let’s talk about why you might need to check your fuel pressure

Why would you check fuel pressure?

• You suspect a bad fuel pump
• You think you have a bad fuel pressure regulator
• You’re getting a rich or lean error code from your engine compute

Before we get started we want to point out this article is talking about checking the fuel pressure on a fuel-injected vehicle.  Carburated vehicles work a little differently so they will have lower fuel pressure and different procedure.

If you think you might have a bad fuel pump, checking your fuel pressure is the best way to prove that.  If you’ve got gas in your tank and a good fuel pump you should have proper fuel pressure.  If you’ve got an older vehicle with a return-style fuel system low fuel pressure could indicate a failed fuel pressure regulator but that is extremely rare.  Fuel pumps do wear out over time so replacing them is pretty common.  Make sure to check the manufacturer’s specification for fuel pressure to tell if your pump isn’t putting out the proper pressure.

If you’re getting a lean or rich error code from your vehicle, one cause could be improper fuel pressure.  If your fuel pressure is too low your fuel injectors will have to stay open for longer to squirt the same amount of fuel into the engine.  Your engine’s computer will notice this lengthened injector pulse and will set the check engine light to let you know something is wrong. The same will happen with high fuel pressure and short injector pulse.

How do you check fuel pressure?

As we mentioned in the video, some vehicles have a port you can attach your pressure gauge to which makes checking fuel pressure very easy.  If your car doesn’t you’ll have to get creative like we did to find a way to check the fuel pressure.  Most fuel pressure gauges also come with an assortment of fittings, “T”s, adapters, and hoses to make sure you can get things set up.  It’s best to check fuel pressure while the engine is at idle to get a good idea of what’s happening in the system.  You can also shut the car off and watch the fuel pressure to see how long it takes for the pressure to bleed off.  If your fuel pressure drops quickly after you shut the engine off it could indicate another part of your fuel system is malfunctioning.

As we mention in the video be extremely careful while checking your fuel pressure.  It takes a good bit of clamping force or a good tight fitting to hold back 50 PSI of fuel pressure so make sure you don’t have any leaks while you’re doing the testing.  If you do spill any fuel ensure it’s cleaned up properly and completely before starting the engine.