420SEL starts then dies
 

Hello everyone,

New to the forum and very happy to be here. I could use some assistance if any of you are willing. I have a 1986 420SEL with 153,000 miles on it and this car has me stumped. It will start and then immediately shut off. I have changed the fuel pressure relay, cleaned all the lines, checked to see if there was fuel at the fuel distributor yet the car is still under the weather. I have driven 5 Mercedes over 2 millions miles in the last 33 years and I thought I had seen it all. This problem is starting to really disappoint me.

If any of you have had a similar problem and a solution to this problem would you be kind enough to opin so that I can get my car back on the road again?

Thank you.

E J Broderick

Surely you have fixed this by now, but when my '86 420 did this, it was the crank position sensor. it would get hot then the engine would die. When it cooled off 10 minutes it would start and go until it got hot again. Replaced it and no more problem.

Have done that.
 

Randy,

Thank you for the advice however, I have replaced both of them. The one at the front harmonic balancer and the one at the flywheel. The tach does not work either. If I take out the relay at the firewall and jump the 30-87 pins, with a wire jumper, the car runs fine but at approximately 3000 rpm's.

Just can't get this solved. Took the car to two repair facilities, have spent well over a thousand dollars and I still have the problem. Car is sitting in the garage and it is a shame. It is truly a wonderful car that looks brand new inside and out yet it sits dormant.

Truly stumped by this.

Thanks for trying to help, I am very grateful.

Edward

Some novice help
 

I know this is kind of a rookie question..but have you checked to see if possibly the cat converter is clogged? It almost sounds like the motor is getting too much back pressure. Anyhow, just a thought.

~P~