Hi All,

Thanks in advance for any advice you can offer. I recently purchased a 1991 300e for fun. It's the gas 2.6L I6 engine. It has 101,000 miles on it, and as far as I could tell is in excellent condition.

Occasionally, the engine will just shut off while driving. This always occurs while pulling up to a stop, and it seems as soon as I take my foot off the gas the tach immediately drops to 0, and the panel lights up. It typically will immediately restart.

I've seen this issue in other threads, but want to add the following, I have no idea if they are related, but I suspect so (?).

The car is hard starting, typically I have to crank the engine once, stop, pump the Gas a few times, and then recrank. It always starts after this procedure.

With the key in 'on' position, but the engine off I cannot hear the fuel pump (passenger rear I believe). I'm assuming that like other fuel injected cars it would prime the system when first turned on? I can hear the pump once the engine is running though. I saw some threads addressing similar issues with an MAS unit--but I do not believe my model has one (doesn't seem to be a cigarette package sized unit anywhere under the hood).

Any advice on these two issues? Are they related? Thanks again for your help!

Quick update... I did locate the MAS unit (behind plastic cover). I jumped pins 1 and 2, as has been suggested, and heard something in the engine compartment running (assuming this is a dual fuel pump system?) but no noise from the rear that I could tell. Could my problem be in the MAS unit? I know it also runs A/C, and that seems to be working fine.

OVP relay is often the culprit. Also, make sure all HT components are 100% with ordinary, cheapo, copper plugs.

Check for vacuum leaks as they often confuse the K-Jetronic - mine's been confused for the 17 years I've had the car.

Good luck.

RayH

Try the Fuel Pump Relay (F.P.R.) often known to cause your exact symptoms.

I have experienced the same problem twice in my 88 300CE (M103) The first time it was the FPR. The (occasional) condition lasted a few months before it finally died. The second time it was bad ignition. Changed the rotor, wires, plugs. Gone.

Although you have a different engine and FI/ignition, my advice is to start with the cheap things & go from there.
IIRC the FPR problem arose about 6 years ago and the odo read around 115,000. The rotor/ignition problem was about 3 years ago@ around 130,000 mi.

My symptoms were exactly the same & the restart was immediate. Got so I could drop it in neutral, restart, shift down into D & not miss a beat.

"shut off while driving".

I had this happen about 10 yrs. ago with my 91 300-SEL. Has the same engine as yours.

My MB would simply die after driving about 8-10 miles and in warm weather only. I'd pull over. let things cool off; then restart and run another 8-10 miles and it would die again while driving. If a cool front blew thru and temps got down in the 50s-60s or lower, the car would not die, but once it got up in the 80s the car would die after 8-10 miles of driving.

Turned out to be a bad fuel pump.

Interestingly enough I also had an engine dying issue that was solved by jumpering pins 1 & 2 in the MAS relay. That gadget sells for $399 on ebay and it's rebuilt. The OVP - overvoltage protection relay has been accused of causing similar issues. It's around $50.

I was unable to find a MAS relay at this forums parts section? Leads me to believe that these "rebuilt" MAS relays are junk. PeachParts apparently stopped selling them.