Here's what Bentley says: "Hot start - Engine starts hard or fails to start when warm a) Insufficient residual fuel pressure b) Cold start valve (injector) leaking or operating continuously c) Fuel pressure incorrect d) Air flow meter faulty"
"Corrective action: a) test residual pressure b) test cold start valve and thermo-time switch c) test fuel pressure d) test airflow meter"
"Engine stalls or idles roughly (cold or warm) a)Vacuum (intake air) leak b)Idle system faulty"
"Corrective action: a)Check for leaks b)Test auxiliary air regulator (or idle speed stabilizer)"
Residual pressure testing: Hook up gauge (You can relieve pressure in the line by a hand-vacuum pump to the pressure regulator so it releases pressure to the tank OR remove the fuse for the fuel pump and run the engine til it dies OR wrap a rag around the connector while you loosen the plug so gas doesn't spray everywhere) Now you can either start the engine or induce the fuel pump to run (you already know how - the vane in the airflow meter) Pressure should be about 2 bar (about 29psi at sea level with no hurricanes nearby!) (With the vacuum line to the regulator pinched off from vacuum or open to atmosphere it should be about 2.5 bar (about 36psi.) Shut the engine off and check the pressure. It should not drop significantly. It should be able to hold about 1bar or more for about 20 minutes.
If you have a set of those nifty plastic clamps for pinching off hoses, (if you don't, get at least a pair, two pair is better!) you can pinch off each injector individually and do the test five more times. Be really careful at this, as the flex lines to the injectors are very short and have been subjected to lots of heat so are possible very brittle.
You can eliminate the air bypass valve as a suspect by either pinching off the lines on each side of it (remember - brittle!) or pulling the lines off and plugging the holes with corks temporarily.
Anything else?
-BH