diamante LS hot soak No-Start

We have a 97 Diamante LS with 3.5L V6. Engine does not want to start on
hot soak condition. Checked fuel pressure and is fine when car is
cranking normally. However when condition exists, fuel pressure will
vary rapidly from 20 psi up to 60 psi. When cracking fuel lines during
condition, appears to be alot of vapor ejecting from fuel lines. Have
tried starting fluid during condition, still no-start. Have checked
spark, spark seems fine on all cylinders. Problem started after
mechanic removed upper plenum to replace spark plugs.

"MotorHead" wrote in message

> Problem started after mechanic removed upper plenum to replace spark
> plugs.

Sounds to me like something was not put back properly eg improperly seated
or sealed, or damaged and not noticed. Fuel pressure should not vary so
much, and there's a pressure regulator that returns the low pressure fuel to
the tank. This regulator may or may not have a control solenoid from the ECU
/ emissions system. If a vacuum hose is cracked you could get the effect you
describe.
--
Stewart DIBBS
www.pixcl.com/lancerproject.htm