High Fuel PSI

[351C Sniper]

Danny, that looks like a good Schrader valve solution. The -6AN Earl’s pressure gauge adapter and Earl's Schrader is a reliable, compact, low cost addition. And that Tool Aid 33770 Fuel Injection Pressure Tester looks like a good tool that may pay for itself many times over.

[Danny Cabral]

I've used this Earl's AT100199ERL adapter fitting and Earl's 100187ERL fuel gauge at the -6AN fuel feed line fitting. The black Earl's adapter fitting has an 1/8" NPT port, which will accept a gauge or a Schrader valve (Earl's 9616SVERL). The Tool Aid 33770/53770 Fuel Injection Pressure Tester uses the common -4 Schrader valve (1/4" flare). Nothing special about it, no fuel mess, and it works great. This Earl's 100189ERL fuel gauge can be used to check the return line pressure if necessary.

Don't confuse the two different types of Schrader valves:
1) An Earl's air tank/tire Schrader valve with a fuel resistant core (5/16"-32 UNEF).
2) A fuel resistant -4 Schrader valve (1/4" flare) with 7/16"-20 threads (LINK/LINK).

And that Tool Aid 33770 Fuel Injection Pressure Tester looks like a good tool that may pay for itself many times over.

Yes, it does. I've owned the inexpensive Tool Aid 33770 for many years, and it's all that's needed with a -4 Schrader valve. There's a Tool Aid 33850 fuel test port adapter hose available (LINK - remains on tool, not vehicle), to keep the Earl's 9616SVERL Schrader valve installed in the Earl's AT100199ERL adapter fitting for the Tool Aid 33770/53770 Fuel Injection Pressure Tester. Or simply use the -4 Schrader valve instead (LINK/LINK); it's only slightly larger, so you won't need a tool adapter at all. Personally, I like the more robust -4 Schrader valve much better. Either way, it's not safe to have an actual fuel pressure gauge permanently mounted on the throttle body, due to engine vibration (possible failure, leak & fire); hence the benefit of a small permanently installed fuel Schrader valve.