SUDDEN DEATH SYNDROME
 

I have a 1987 300E US automatic sedan. In short, the car likes to stall when making a right turn (used to be a left turn but has now shifted to the other side). The problem usually manifests itself after the car has reached operating temperatures and has been running for a while. Warmer weather brings the onset of the symptoms earlier in the operating cycle. The vehicle will run fine but will initially sputter when making a right turn. Shortly thereafter, it will start stalling on right turns and eventually will sputter and stall when decelerating to a stop. The car initially restarts right away, sometimes while the car is still coasting and you shift into neutral and crank.
Eventually, you have to come to a full stop, put it in "Park" and then start cranking - which takes a couple of more attempts before it starts up again, and sometimes it helps to relieve pressure from the gas cap but not always. This used to happen sporadically, over the past two years, and has been impossible to diagnose. Now it happens every time the car runs in stop-and-go (not highway) traffic for more than maybe 30 minutes.
Master Techs! HELP!

I'm no Mercedes Master tech, but mine did something similar for about a year and it got worst and worst over the year. I too tried the gas cap trick, but it got to a point were I could leave it alone for an hour, and try a few times and it would start again. I brought it in twice but it would never replicate the issue until I brought it in the third time. It was the fuel pump. When we tested it applying 12v to it...it only work 50% of the time. The mechanic told me that it when the car would start ...the fuel pump didn't have to work as hard or some of the time to keep the car going...but my 95 w124 e320 did have a dual fuel pump too. He replaced just one at first but the issue resurface (he didn't know my model had a dual pump until I told him:)). So he replaced the 2nd pump and the issue was resolved after a 10months of head scratching. We replaced the fuel filter while we were at it too. Good luck.

Or maybe the fuel pump relay. That relay supplies voltage to the fuel pumps, and its internal solder joints flex with heat as it ages, causing intermittent pump function, until the solder breaks entirely, and then the car won't start again. Simple plug 'n' play replacement, and not terribly expensive from I-net vendors.

Cal...that's a good point and I will keep an eye on that relay if my issue comes up again. You are so right about those old solder joint getting old and cracking. I had an issue with my Hazzard light and Turn signals working on and off...turned out to be a three cracked solder joints in a relay, you could actually see the joints cracked with your naked eye. I was able to re-solder them together with a help from this forum and BINGO. But a used one was just 25-40 bucks if I messed up:).

Relay Gremlin???
 

Thanks for replying guys. I have two fuel pump relays purchased new less than 18 months ago - the newer one of them is in the car now. I will go back and re-cycle through both but I'm not hopefull that this will solve the issue. The OVP is less than 18 mos. as well. I will probably have to replace the fuel pumps soon. Any idea for an inexpensive supplier?

Don't replace the pumps until you have ran a fuel pump quantity test to verify either a possible restriction or weak pumps. Fact is pumps are about $130/each, you won't really find much of a "deal" on them.

I did an article on it here:
http://www.w124-zone.com/articles.php?article_id=48