Troubleshooting 8.1L fuel pressure loss - looking for a tool

[jocko]

Recent issue on my 01 8.1L wherein it doesn't always start on 1st try. ALWAYS starts on 2nd try, if required. Started working thru the troubleshooting tree, and have correct pressure on a fp gauge w/pump on. Once key off/pump off, pressure bleed-down exceeds specification (limit is 5 psi in 1 min, I'm seeing at least 10 psi loss in 1 min). Have verified no dripping/leaking at the pressure regulator, so suspect either a leaky injector or a bad fuel pump check valve. BUT, to isolate the issue between the two before ripping stuff apart further - the next step per the gm big book is to install the "fuel pressure test kit inline shutoff valve(s)" between the fuel rail and fuel feed (and also return) line(s).
I've got a pretty dandy fp test kit, it's based on J37287, the test kit gm calls out, but no such shutoff valves in it. Any idea where to find such an animal so I can isolate my problem a little better?

(or an alternative idea on how to test to figure out of it's the check valve or a leaky injector?)

EDIT: my only other clue is that on RARE occasion, when it doesn't start on the 1st try and I shut the key off, I hear a bit of a hollow metallic thud from the tank - like the dang gremlin is actually in there and bangs one time on the inside of the tank in an effort to get out(!) ha. My gut feeling is this issue is the check valve and maybe it's time to swap the pump out of the tank. Truck has <20k mi on it so it's had not seen much use before I bought it. Never any issues with it running perfect once it starts and it always starts on the 2nd try. SOMEtimes on the 1st, but more often than not, have to shut the key off, re-attempt start and it fires right up on 2nd try every time.

[hatzie]

Can you install a valve in the middle of your test kit piping?
I modified a fuel injection test set back in the 1980's so I could test the Bosch CIS setup on my VW. It had the proper threaded and banjo connector ends but lacked the valve to test the control pressure regulator among other things.

[jocko]

thanks Hatzie, that's exactly what I need - but am kinda hoping there's an available test part out there that does this, otherwise I'm cobbling together a homemade set of GM push-fit metal clip lines to get the job done - and the seal is critical since I'd be testing pressure bleed-off post pump power down. Haven't been able to find such an animal - and maybe incorrectly assumed it'd be available off the shelf. I'd have to assume a GM mech doesn't cobble together something whenever they are troubleshooting this at a dealership, so seems it should be out there somewhere. I may need to look a little more, might be looking in the wrong place.

[jocko]

Just to follow up, rolled the dice and assumed it was the pump since there were no lean engine codes and because it ran just fine once started (so I mentally ruled out a leaky injector). New pump seems to have resolved the problem - checked the pressure bleed down for several minutes and there was none.