There are lots of posts targeting the Fuel Pump Relay with these symptoms, but so far it appears to be caused by another component that's temperature sensitive.
Car starts fine quickly, but before reaching full warm-up to ~83C, car dies. I'll attempt a restart & partially turn ignition key, Fuel Pump can be heard running. If I let car sit for a couple minutes, it will start , but stalls after ~ 30 seconds.
I jumpered Terminal 30 to 87 on the FPR Block. Fuel Pump runs, but no start. After car stalls I pulled a Ignition Wire, installed Spark Plug, layed on Valve Cover & tried restarting. Sparks seen across Electrodes, so assume Ignition System not the cause. I have flushed the Fuel Tank, replaced Tank Filter,& Fuel Line Filter. I checked the Warmup Regulator System & Control Pressures & they are fine.
Attached is a wiring diagram related to the FPR, that I found on the internet.
I look at how simple the Fuel Pump wiring is on my 1980 280TE. No need for this big Relay.
Can anyone think of a temperature sensitive item that might be stopping the restart?

Attached Files

1985 Mercedes 280SL Fuel Pump Relay Wiring.pdf (426.7 KB, 19 views)

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80 280TE, 5 speed
83 280TE- 5 spd, 16.5mm rear sway
85 280SL- 15" Bundts

Has the engine been Federalized? Does it have a lambda controller/frequency valve/O2 sensor package? If so, is it European/OEM, or aftermarket?

All the anti-Pollution devices have been long since removed. I'm wondering if the Warm-up Regulator might be intermittently drawing too much current. The wiring dwg appears to show the FPR Power comes from Alternator & Warmup Regulator. After it was near fully warm & had stalled, I unplugged the WUR. Car idled higher, but didn't stall idling in garage for ~5 min.

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80 280TE, 5 speed
83 280TE- 5 spd, 16.5mm rear sway
85 280SL- 15" Bundts

FPR power (30) comes from B+, and is always hot. The fuel pump and the WUR are both powered from 87 on the FPR (switched power).
The WUR could be a bit out of calibration and raising the control pressure too much.
Try taking a 1/4 turn rich (CW) on the main mixture screw. If that cures the stalling, consider a re-fresh of the WUR, OR, just run it that way!

Can anyone tell me where the Cold Start Valve Thermo Time Switch (#15 wiring diagram) Switch-over Valve decel shutoff system (#36) & Decel Micro Switch (#37) are located?

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80 280TE, 5 speed
83 280TE- 5 spd, 16.5mm rear sway
85 280SL- 15" Bundts