560 SEL recently had major overhaul (valve job, etc. etc.) runs smooth, great. City driving, highway driving the car performs superbly, lots of power. But.....until this overhaul, there would be the expected sound of release of pressure when gas cap removed for refueling. Since overhaul, no sound.

Only two symptons of this change. Starting is slightly delayed on ignition. Worse, engine stumbles -no power- if vehicle passes through standing water (~5 inches). Engine recovers after coasting to the side of the road.

Obviously, the driver should avoid standing water. Now that we have that remedy listed, what else is there that could have been unconnected, misconnected, etc. during that major overhaul that would cause this problem?

I assume you did not do the overhaul work yourself.

If that’s the case take it back to the shop that obviously did not do the job correctly and demand the engine run as it did before the work.

This is not your problem, it’s the shop’s.

Problem appears to be solved after replacing original wiring harness to the fuel pumps- Part #126 919 07 20 - (it was difficult to locate this OEM replacement). Intermittent short of fatigued wiring near fuel pumps apparently caused random interruption of their operation while car passed through standing water. Car did not stall/engine did not quit during the seconds the pump(s) stopped, but it was a dangerous, helpless feeling for the driver.