31st Aug 2010, 13:31

I have a 1990 420SEL with 109,000 miles on it.

The key to these cars is to have a good technician and take it in for maintenance items. These cars are a lost art. Due to using plastics and lighter weight metal, the new cars just don't last. These older Mercedes were built with the idea of handing them down from generation to generation. Europeans don't buy a new car every four or five years. My tech. tells me that these cars are easy to diagnose and repair.

As far as cost goes, take a Toyota in and see what you will pay for repairs for parts made of plastic. I know a dentmaster repair man who dreads taking dings out of American made and Japanese made cars. In his words, "The metal is junk!"

You can't lose with a well taken care of Mercedes 420SEL.

5th Oct 2010, 18:39

Less than 24 hours ago I became the owner of my first 420 SEL. It's a gorgeous 87, silver with wine leather. She is gorgeous, but I tried to start her this morning and no go. I love this car, but am now a little concerned I may have bitten of a bit more than I can chew. The car only has 109k on it, so I am hoping I can overcome any abuses that may have occurred.

The motor and trans are strong, the car is solid, it's just the electrical system that is giving me problems. I knew there were some problems, but it started and ran strong, not a spec of rust, not a scratch on the paint.

The leather, for lack of a better word, is perfect. I have never seen this color interior in one of these. I mean maroon leather, 109k in miles, and a $1250.00 price tag. Well I just couldn't resist.

My question to you guys is, did I make a good deal. Is this car going to get me where I need to be for at least a year? What is my worst case price to fix all this electrical crap? Will this car pass PA emissions testing? I mean, are there no inspection stickers for a reason?

18th Oct 2010, 12:11

I own an 87 420 SEL with 157,000 miles, no major problems. One of the best vehicle ever made!

19th Dec 2010, 20:31

I have a 1987 420 SEL. After jump starting my wife's 1998 Sable (correctly) two times in two days, my car will run and then die after a trip round the block. It was jump started OK, but now jump starting does not succeed. It cranks OK and seems to want to start, but then acts as if there is no fuel. It normally fires immediately on the first crank. I note that a triangular orange light now comes on adjacent to the fuel gauge. There is about a quarter of a tank of fuel. I have relieved the pressure by loosening the gas cap.

OVP, FPR or a new battery? Help and thanks.

21st Apr 2011, 14:06

I have exactly the same problem with my 86 420 SEL.

It has been a year with no fix.

What about the cam position sensor? One tech said they fail just like the crank position sensor i.e. from heat, and self repair after 30 minutes or so???

24th Sep 2011, 00:21

Take the air cleaner off and have a friend press the gas pedal. Check to see any there's binding on the linkage; it should move freely. Also check the over voltage protection relay while the car is running. Pull it out, and if the rpm goes up, it's not the problem; plug it back in.

5th Oct 2013, 03:53

I have a 1989 420 SEL. Same problem. Ignition switch was the culprit. $402... no longer a problem. My car has 251,758 miles.


3rd Dec 2013, 00:52

Hi, I'm Larry, I own an '89 420. I corrected my high idle problem by changing the OVP regulator, the car runs great, but I have no start after it gets warm; I'm thinking electronics? I don't have a service manual, but I'm working on it. I'd like your input 714 4040184. Thanks.

3rd Dec 2013, 12:35

Similar problem with an old Audi I had - one of the relays had a hairline crack in the solder, so after it gets hot, it won't start. Mine was a more centralised "engine control" relay; not very big.

21st Feb 2014, 00:36

This is Larry. So glad that someone read my comment about correcting the high idle problem by replacing the OVP regulator, which governs the amount of voltage to the computer. Sorry I left out that the idle / OVP regulator lowers the high idle problem.

My current problems are the factory troubleshooting manual. My 89 420 SEL runs perfect except for the high idle problem I had. Now she won't restart when it's hot (80 degrees & above). I go to restart, but it only cranks, but if I pour a little gas in the throttle body, not touching gas pedal, it starts. If it doesn't start, trying again has been my solution for now, so the solution is study the trouble shooting factory manual. The potential cures so far are the fuel pump accumulator and fuel distributor? I have very little money, but I'm grateful that someone took my advice. If there's anybody with advice, contact me at 714 404 0184.