With crush washers widely available for less than $2 each, it hardly seems to be any bargain in terms of ease of effort to choose removing the glow plugs down in the abyss between the IP and the head with their easily dropped wire nuts, and awkward access, over removing the injectors and testing with that adapter. Just time wise alone I'd bet it takes three or four times as long to get the glow plugs out compared to getting the injectors out. And properly done a compression test should be done on an engine at operating temp so getting down to the GP's can be uncomfortable as well.

If when replacement injector return lines are installed their loops are made a couple inches longer than the minimum length required they can easily be reused by just cutting them off just above the nipple loosing only the 8 or 10 mm on each end whenever they need to be disconnected, so you can avoid replacing them in their entirety each time doing it that way as well.

Because the internal space of either adapter is not a great portion of the tester system's overall internal space and because the tester total system volume effect on compression pressure is reduced by an order of magnitude with each subsequent compression stroke's pressure accumulation.

I'd be very willing to bet that the tester gauge tolerance far exceeds any significantly measureable inaccuracy that could be induced by adapter choice.

Only by ignoring the insignificance of any such adapter differences and ignoring the operational functioning of the tester system could adapter choice have any effect on measurement outcome.

Test at operating temp, properly connect a functional tester system, and follow established procedure of ensuring at least 8 rotations of the engine per cylinder test, and there can be no significantly measurable adapter choice effect.

As mentioned above it is a lot easier on an OM617 (rather then the OM603 I assume you are talking about)

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!