For LH injection motors:
Visit local Enzed or similar industrial hydraulics store. You will need: 1 mechanical pressure guage to 100psi. 1 only 14mm banjo fitting, and another to fit on your pressure guage of the same hose size.. 2 copper or aluminium washers to fit either side of the banjo. >1M of suitable hose, abt to take up to 100psi, and 2 worm drive hoseclips to clamp the hose to the hosepipes. PTFE tape. Abt $AUS45- all up here.

use PTFE tape to attach guage to hosepipe without leaks. fully connect the hose to both hosepipes, tighten clamp at each end-tight, but not cutting into the hose, and keep washers clean and flat.

With ign OFF, and a (preferably) COLD motor, carefully undo the fuel connection at the injector rail using 2 spanners so it won't twist, expect brief spray of fuel. Clean both side of joint. Slide onto bolt 1 soft washer, the banjo, the the other soft washer, refit the fuel line and tighten firmly with 2 spanners. clean up spilt fuel. Turn on ign and check for leaks, then read guage.

start motor-observe guage readings at various modest speeds, Have someone else stand on footbrake and put car into gear, then read guage when motor reved up under load, inc a few sharp gunnings of throttle from modest and low RPMs.. do not prolong this test. return motor to idle and engage N or P. Check for leaks. Shut down and think. What was the initial reading? Did guage move much, and if so, when and how much? What were the highest and lowest readings-when?

Ideally: you should get 68psi to start with, and as lowest reading. There should be some brief increase in reading when motor sharply gunned. The increase is several psi, perhaps 10(?)psi at most. System should hold pressure on shut down, and for at least several hours thereafter.

Discrepancies from ideal may indicate bad pumps (overall bad pressure), bad filters(worse pressure with more load & speed) , bad regulators(overall bad pressure), leaks(pressure falls after shutdown.), blocked/crushed supply plumbing (see bad filter), blocked/crushed return plumbing(overpressure), intermittent pressure spurts(bad electrical supply to pump), etc.

Remove guage system from car before driving off. Take care with fuel spillage on hot motor. No naked lights or flames. Repeat test periodically or when motor goes sick, just to eliminate fuel supply from the mix. This does NOT mean the fuel metering is ok!!!!!

Preserve soft washers, they must always be used, and be in good condition-bent or scored ones will leak. Keep spares on hand. You can use fiber washers here too, but be careful, they're fragile.

A bit of a pain without the Schrader valve. Both my Fords have that valve and it's a simple connection. I have yet to rig up a fuel pressure test on my Volvo. Thanks for the write-up.