The last I remember, the car wouldn't start. Did you get that problem fixed? Did you ever get the ignition working? As far as the air plate being down, you can also add a leaking check valve at the output of the pump/pumps causing the pressure to drop.
I am not familiar with the 2.8 engine at all, never worked on one but the air plate in my 117 engine is always up, with or without fuel pressure. It has no springs, but does have balance weights that keep it up until the engine is started.

PaulM

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84 500 SEL (307,xxx miles)