I recommend that you watch fuel pressure following the warm shutdown, and on through restart. It can take a bit for the relatively cool fuel to push and compress the superheated vapor back into liquid or the tank.

Try connecting your trusty switched relay jumper to the fuel pump relay socket, and run the pump for 30 secs or so before cranking for restart. 30 seconds of pump running should restore liquid state to the fuel in the rails, and none of your heat-soak symptoms should be there. If that seems to solve the symptoms, do a real pressure and flow test on the pump, watching the pressure decay with the engine still cold. Looking for leaking injectors and/or leaking check-valve, leaking FPR.

 

^^^^^I will jumper the pump relay next week and report back. I have recently replaced both rear pumps, and did the flow test with a timer and a jug, and that tested right on spec. have not test with pressure gauge. injectors were just balanced and clean, and I don't see any visible leaks. how to test check valve and FPR?

 

Pressue gauge will show pressure at idle (slightly lower) and revved. There will be a spec for pressure loss after stopping engine - should be x psi after y minutes - if much less suspect check valve, or a leaking FPR or injector. Check for FPR leak by pulling vacuum line and sniffing for fuel odour.
jp 83 Euro S AT 57k

 

Heat soak always results in sweaty underpants.

 

And reduced fertility!
jp 83 Euro S AT 57k

 

I don't need no stinkin' fertility!

 

tested both dampers and FPR with mityvac and all held vacuum successfully. BUT, the rubber elbow at the rear driver side damper was torn badly, and surely leaking.
replaced the rubber elbow, (keep a few new ones in stock)., so that is resolved.

can someone tell me the symptoms of that issue? would that vacuum leak affect the FPR? pulse issues at the rails? (not able to drive until weds.)

 

A loss of vacuum at a regulator could lead to rich running at idle. High vacuum is used to reduce the spring tension on the diaphragm to reduce the fuel pressure at the injectors and lean the mixture. If the regulators are interconnected one leaking vacuum might distort the vacuum they both see, but would at least affect one fuel rail.
jp 83 Euro S AT 57k

 

thanks for the schooling; I would have thought loss of vacuum would create a lean condition. would the loss of vacuum at the damper, cause loss of vacuum at the FPR, as well?

 

Depends on the size of the tubing connecting them. See if you can get a vacuum gauge into the tubes , see what vacuum at idle is with the old damaged tube in place, and after its fixed. if there is not much obvious difference I doubt that was the cause.
jp 83 Euro S AT 57k