Optimum approach would be to check fuel pressures, both residual after sitting, and when running, and to monitor EHA current during start-up.
These tests of course require some amount of special equipment.
Some quick checks would be:
- Try pouring an ounce or so of fuel into the air valve and then starting - if it kicks right off, then it's definitely fuel delivery issues.
- Another test, before trying to start a cold engine, turn the key on and listen for the fuel pump hiss for about 2-3 seconds; then turn the key back off and back on, to make the pump run for 2-3 more seconds. repeat this for 3-4 times, then try to start the engine. If it helps, then you are losing pressure thru the accumulator, check valve, injectors, or fuel distributor.
- After running the car, let it sit overnight, and loosen the fuel line going to the fuel distributor - it should still have some pressure. If not, see above & do a search on testing accumulator, check valve, injector leaking, etc.
- Get a Sears multimeter #82139 with a Freq/duty cycle setting ($32). Read the meter instructions for setting up duty cycle test, and hook it up to the round diag connector on the left fender well - red to pin 2 (gnd), black to pin 3 (DC signal). Read the duty cycle when first started, should be 50%, then when it warms up, should vary up/down abound 45-55%. If it's off, need to try adjusting the air valve screw - do a search here.

Lots of other things, but these are a good easy place to start a meaningful diagnosis. And, yes, the cold start injector doesn't fire above 60 degrees, but the EHA valve does draw significant current (12ma or so) to enrich the mix during cool (>60) start.
If the above does not indicate a fuel leakdown problem, then a good next step woud be to build a little wire harness with male and female bullet plugs to tap into the EHA valve wires with the sears meter above, and measure the current during cool start (12MA) and warm running (1-2 mA). These results will open he way to the next can of worm in the search.

DG