I bought an 87 420 SEL from a guy last week, not running. He told me the only reason it wouldn't start was because the delivery line from the tank to the fuel pump was cracked. I replaced it and the engine still won't start. I did a compression test and it's excellent, almost 160 PSI on all 8 cylinders. I opened up the line going into the fuel distributor and turned the key, gas came shooting out, so I know I have fuel pressure. All cylinders are getting a spark and the timing is perfect. while I was doing the compression test and had the spark plugs pulled, I checked them, they were clean, I tested for a gap with a feeler gauge and they were fine. the starter is good and the engine turns over fine. I even poured a little gas into the intake plentim. Still nothing. I'm stumped.

 

I have an 1987 420SEL. Same year and model i have 109,000 on it and I rarly drive it. I would have to say to is get it lookd at by some one who deals with Mercedes. Where are you located? Are there any independant shops near you?

 

wow! 109,000? I thought 130k was low. jeez....
I live near Sacramento CA. There are plenty of shops, I just don't want to send it to one because I'm on a limited budget.. Plus, I'd like to learn how to work on the car myself. I'm confident there's nothing majorly wrong mechanically because I bought it from a wealthy S-class collector who religiously maintained his fleet and sent them to the dealer for full fluid flushes and tune ups every few thousand miles.

He told me that the engine started running really rich right before the fuel line cracked. Right after I started this thread, I talked to my friend who's also a Mercedes enthusiast and he said a leaking cold start valve could be causing my problem, as it causes the engine to run rich and eventually prevents it from starting because it floods the combustion chambers and fouls the spark plugs. So I'm gonna pick one up from a local auto dismantler for $40, install it and cross my fingers that the engine will start.