'86 420 SEL: Cutting out/Stalling - PeachParts Mercedes-Benz Forum

Randy · #1 03-29-2009, 12:20 AM

HI, Took the 420 to a wedding this afternoon; bought a tank of super about 20 miles from home; about 20 miles later, the engine cut out or stumbled for a second as I turned a corner. 10-15 miles later, it bogged and died on the road. It started right up, idled perfectly and drove fine, then about 10 miles later, same thing. I made it to Natchez, and it ran fine about the last 15 miles. I started home, and about 20 miles into the return, it started cutting out and stalling again. I could usually back completely off the accelerator for a few secouds, and it would pick up and run fine for a few miles. Sometimes it would quit completely, at which time I went to neutral, turned the key off for a few seconds while coasting, then it would restart and go on. Toward the end of the return trip, I stopped for more fuel, thinking it might help. Problem seemed to get much worse, finally it would run smoothly and pull for a few seconds to a minute or so at a time, then stall. It would always restart and run fine for a short while. I called the flatbed and made the last 10 miles in shame, thankfully it was at least dark. What do you think? Bad gas? Fuel filter? Fuel injection problem? Ignition? I bought the car not running in Dec 2003, replaced both fuel pumps and the filter, and it ran fine then. Have put about 7000 miles on it since then, I did change the timing chain and guides and tensioner a couple of years ago; had 7 degrees stretch in the chain, but guides looked OK and the tensioner seemed good but I replaced it with an OEM part.

E150GT · #2 03-29-2009, 10:11 PM

probably bad gas if it happened after a fillup. Especially at a station you are unfamiliar with.

Randy · #3 03-29-2009, 10:24 PM

Thanks. I got in this afternoon and it started right up and idled perfectly, smooth as silk. I drove it down the street about 1.4 mile and turned around, no problem. As I recall yesterday, there was no problem for the first 15-20 miles of my return trip, then it got progressively worse as I drove, to the point it would hardly run more than a couple hundred feet. I had to continually restart and ease along. It got much worse after my Bright Idea to buy some more gas, hoping it would help; I think it just stirred everything up.
Anyway, I am planning to clean the tank out, probably drain then remove it. Any surprises here that I should be aware of? I'll order a new filter, too.
This station is a relatively new Chevron store, but I bet it doesn't sell much premium. I have never had any problem with the reg UL for the company car, but a Taurus will eat about anything.

professor · #4 03-29-2009, 10:30 PM

You may want to check this post
1987 560 sel, bad fuel distrubitor ?

E150GT · #5 03-29-2009, 10:36 PM

If you change the filter make sure you get all the copper crush washers and be prepared for a fuel leak in the rubber lines down there by the filter and pump. Thats if they are original. If you find they are, I would just go ahead and get new washers and fuel lines ahead of time. I did this job on a nice sunday afternoon, and as I put it all back together, it sprang a leak at the rubber line as it was old. The next week turned cold and rainy. I had to air freight new hoses in and replace them in the wet cold. Good luck.

Randy · #6 03-30-2009, 09:36 AM

Thanks, Professor, I ddi read that thread. Fuel distributor was my first thought; after all, my car is 23 years old. However, if it were bad, would the engine ever run and idle perfectly? Thinking about Sat night, how it got progressively worse, to the point it would only run a few hundred feet and quit, but would restart every time, I would not doubt the distributor is shot. I am going to check to see what's in the tank before I assume it's something worse.

david s poole · #7 03-30-2009, 10:01 AM

check out the crank trigger to the ignition unit.when they go bad it will exhibit exactly the symptoms you have.when they heat up they quit.it is located at the bell housing just to the drivers side of centre.the original ones had a green sheath over the cable[it goes all the way to the ignition unit behind the left headlight]all the replacements had black sheaths over the cable.when it goes bad the car will run well until it heats up and then it either quits or runs badly.

Randy · #8 03-30-2009, 02:05 PM

Thanks, David. I ran across this item in earlier reading and needed just this information to clarify. I will indeed check this item.
Regards, Randy