I'm going to guess that you have a small leak that is allowing air to get into the fuel system. I know you already checked the fuel lines, but it's probably a really small leak that you missed. Since you don't have fuel leaking out, I would further speculate that the leak is on the suction side. Since you've already tried running it from a container instead of the fuel tank, I'd concentrate my inspection on the last bit of line going to the injector pump, and also check for a leak on or in the pump itself. It may be helpful to pressurize the fuel system in order to help find the leak.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.