Okay guys,I've been asked by our lesser-valved(but mighty P7100-equipped) friends to adapt this gauge to 12 valve systems. So, after a little investigation, here's the scoop on using my fuel pressure gauge on 12 valve systems. I believe you'll need a gauge with a range of 0-60psi, instead of the 0-30 I'm using for the 24 valves. The fuel filter mounts have threaded and plugged ports on top of them, which means a gauge hookup is as simple as installing the same extra fitting that I supply to the guys with 98. 5 thru 99 trucks. The 2001 thru 2002 trucks, the hose hooks straight to the injection pump test port, or the one behind the fuel filter.
My special fitting for the older trucks simply converts the plugged 1/8NPT threaded port into a "schraeder " valve, just like what's on the newer 2000 & up trucks. Just the fitting can be left in place, if desired, though it's a good idea not to leave the gauge itself hooked up all the time! This is a temporary test gauge, and while it's plenty strong, our service manuals recommend against leaving one hooked up on a semi-permanent basis, as vapor lock can occur... .
Any of you 12 valve guys care to post a link to this thread in the 12 valve forum? And please look at your fuel filter housings for me, to confirm you have those threaded & plugged ports on there. Thanks !