At the fuel filter, disconnect the quick connect fitting and connect both ends of the tester. One end to the line that you removed and the other end to the filter. Fuel needs to flow through the tester to check pressure. Open the valve and turn the ignition to the ON position and read fuel pressure while the pump is running. To test maximum pump output pressure, shut the valve off and turn the ignition to the ON position. Check pressure while the pump is running. For testing leakdown, open the valve, turn the ignition to the ON position. When the pump shuts off, (approx 2 seconds) immediately shut the valve. If pressure drops below 55psi, the leak is in the tank. If pressure remains above 55psi, the leak is in the plenum.

EDIT: The ball valve and the brass fittings are available at Lowes, Home Depot or any good hardware store, (in the plumbing department). The rest of the parts are available at any good auto parts store. The quick connect fittings are made by Dorman and they are both for 3/8" line. Max pump output is 78psi to 108psi, (the gauge I used only goes to 100psi) so keep that in mind when getting a gauge. Seems to me Harbor Freight has gauges too.... cheap.

 

That makes complete since! Now I need yo make one so I can give her a test.

 

I already have one, in fact, I also made one for the return line for diagnosing the regulator and injectors for leakage. Make sure you use "Fuel injection rated" line.

 

i meant to say *to* and not 'yo'. you can thank the autocorrect for that.

 

im having same problems on my 99blazer.went to autozone and gave me the same codep0300.ive got 199858 miles on it already and im about to get another engine for it this week for 450 from a mechanic i know. code gave me ignition system fault spark plug,ignition wires,coil,vac.leak injector fault,high or low fuel pressure.i sometimes have to pump it too,and its giving bad exhaust fumes even when im at a red light smells like firework powder when it pops and running rich too,rough as well i went to a web site and gives gen.ifo.bout this it said to check maf sensor that the wires could be dirty and might not be reading airflow rite.my exhaust tips r black too did normal tuneup on it and nothing,even changed map sensor which wasnt cheap.i even have my cluster lights flickering a little bit.when i turn it on at times my rpms wont hold bcause it feels like its going to turn off so i have to give gas for a bit.i have never had this problem ever.helpthis web site is called easyautodiagnostic.com

 

I just checked my sparks, changed wireset and its still running rough. While I was looking over the engine I noticed that there was a cracked hose, from what I can tell it goes to the air check valve, the rubber hose is a small L shape. Would that be a possible reason as to why it might misfire or run rough (aside from bad motor mounts to which I just replaced one of them)?

 

Can you post a picture of it?

 

Hell blazer: How many times we have to tell you you are running rich! Dirty MAF gives a lean condition. So it aint your MAF unless it's broke.
Either run the freakin fuel pressure leakdown test. Or quit posting till you do.
If you dont do something soon, you may ruin your catalytic converter.

See how I separate my points, there? Quit irritating us and write like an adult.

Klturi:
Sounds like the PCV valve tube but I agree with the good Cap'n... A pic would confirm. Whatever it is, a cracked line needs to be replaced.

 

Here's the hose/pipe that has the crack in it.

 

That's for the secondary air system, it needs to be repaired but it has nothing to do with misfires.