Hi everyone....I'm new to the forum and I'll jump right in with my current problem with my car -->

I have a 1997 e420 sport that I purchased last summer. I absolutely fell in love with the way this car drives and handles and I've been fixing it up to 'like new' condition (it has 120,000 miles on it, but looks brand new). I didn't mind putting a few thousand into repairs and maintenance over the year, but since January I've been experiencing an odd problem and would like to know if anyone has had a similar experience. I went to start the car one January morning and the starter just spun without engaging the engine. I had it towed to my local mechanic and he got the engine to turn over, but there was a significant loss of compression and he couldn't figure out what the problem was. He suggested I have it towed to the Mercedes dealer (Plaza Motors in St. Louis). They diagnosed it as a bad crankshaft positioning sensor, replaced it and the car was fine again ($540). I gulped, paid the bill and gratefully had my 'ride' back. Everything has been great until last Sunday, when I got in the car and had the same experience - The starter whined away without engaging the engine and the car was dead in the garage once again. This time I had it towed straight away to Plaza, and indicated that it seemed to be doing the same thing again. They got into it and found the same mysterious loss of compression my mechanic reported back in January. He suggested a complete engine tear down to determine the problem ($2100 for starters, with the promise of more charges for repairs). He felt the head gasket might be blown or several cylinders may have gone bad. The car had absolutely no symptoms...no smoke, no loss of power, no indication of any problem whatsover, so I have a hard time believing what he told me. When I tried to get him to consider the identical symptoms as earlier this year, he said it couldn't be the same problem as before. After consulting with my local mechanic, he suggested a second opinion from the rival dealer in town (Tri-Star Motors) and the service guy I spoke with agreed that the lack of symptoms prior to the breakdown made no sense. I had it towed to the second dealer($75), but not before Plaza charged $385 to my credit card for 'diagnostic services' before they would release the car. From what I can tell, all they did was remove the spark plugs and check the compression. I'm really upset with the whole mess and now must wait until next Monday before they can start on my car. I still have no idea what is going on to cause this bizarre problem, and I'm out $450 so far on this current nightmare. I'm actually considering selling my 'baby' once it is repaired and taking a significant loss due to the $$$$ I've had to put into it. The car is beautiful and I love driving it, but now I feel it will never be dependable......Any encouragment, advice or other input would be appreciated. Thanks! Scott

 

If it were any other car brand I'd say it needs a new starter solenoid judging by your description. That's an easy one for a mechanic, though, so I guess it's not the solenoid.

I can't imagine why the starter would spin unengaged if the engine loses compression. Also, how are they testing for compression if the starter doesn't engage?

Germans think in weird ways. They probably put the jelly on their bread first then put the peanut butter on top of that.

 

The starter wouldn't engage when I went to start it, but when it got to the shop, it engaged fine, but their compression testing showed a significant loss in compression. I can't see how these two things are connected.....anxiously awaiting the second opinion from dealer #2......hopefully I won't need to take a second mortgage to get this problem resolved.

 

the two problems is not related with each other.

Lugnut was right, it was the solenoid. it often gets faulty and intermittent too.

120k miles is enough to wear out the piston rings, valve seat, and other parts.

 

[8|in the cold weather your starter cant engage is your oil too sticky.starter have weak motor or your battery weak in cold weather..if your car sitting too long like a few weeks...once you start your car in cold ,it will very easy to cause your e420 timing chain jump the teeths ....and make it hard started or cant started.
if your engine have missing compression ,why dont you check the timing mark at the # 1 cylinda for make sure your chain dont jump before take your engine head off....
just a opinion....

 

Got my e420 back......got towed from dealer #1 to dealer #2 for second opinion....started right up for dealer #2 and all functions checked out normal. Compression was fine, no computer codes, no starter problems. It's a huge mystery. The working theory is that something is causing fuel to flood the cylinders, washes them down and hence the loss of compression. Once the car sits for a few days, the fuel dissipates and the rings can once again seal.....and the car runs fine again. This has happened twice in 6 months, and they can't determine what is causing it. I got Plaza to refund my $385. Their diagnosis would have led to an engine tear down that wasn't necessary....thank goodness I sought out a second opinion. Happy to be back behind the wheel of my 420.....

 

You have at least two problems. Even if the "working theory" correctly predicts the cause for the loss of compression, it doesn't explain why the starter spins without engaging.

There would be black smoke at start up if gas is leaking into the cylinders to the degree to which the working theory implies, unless the gas has completely evaporated each time the engine starts except for those times that it won't start. But you have to believe that some gas would be left after a major incident or that some gas is beginning to build up. I doubt this theory if you never see black smoke at start up or never smell gas when you're near the car. It would be obvious during a compression test that shows no compression, if a flood of gas is causing the problem. The mechanic would get high from sniffing the gas fumes.

There would be white smoke if a head gasket were blown. You'd probably be able to hear a blown head gasket. Not always, but they usually will sound like a metallic click. You'd also probably see coolant and/or oil puddling beneath the engine.

Has anyone checked the PCV valve to make sure it isn't stuck or gummed up? It wouldn't cause all of these problems but it will give you and indication how dirty the mechanical innards may be. Remove it and shake it vigorously. Does it rattle freely with crisp, clicking sounds?

Consider getting a CarFax report. Cars act weird after they've been in major accidents or caught in floods or restored from a salvage condition.

 

you're right lugnut, it's not a fuel injector leak.

all fuel injectors cannot leak at the same time
only the older version of fuel injector leaks (CIS, CIS-E) or the mechanical type.
if ever the fuel leaks inside the cylinder, you must have a bent connecting rod now
the car will still start even if there is a flooded cylinder
the compression will go high instead of loss if there is fluid in the cylinder
your oil level will go high because some fuel goes down to the crankcase
backfire can be heard either from intake manifold or exhaust pipe

so what's the real problem of your car doctor scott?

 

Thanks for the input......I'll have the PCV valve checked as you suggest. I did get a Carfax on this car before I bought it, and it came up clean. When reviewing service records from the dealer when I first had it in for repair, I found it had been in a few significant accidents in the last two years involving some extensive body work, so how accurate can the Carfax be?

The last mechanic did get some black smoke when the car started, so that would support the fuel theory I guess. There is no pooling under the car and I never smelled gas during either incident.

I'm going to keep driving the car until it happens again, and hopefully I won't be out of town at the time. I'm also considering trading it on a newer Benz with less miles if I can find a comparable car.

 

One of the three mechanics mentioned the danger of bending the connecting rod if this problem continues.......that's when I started thinking about getting out of this car.

They ruled out a fuel injector leak...like you said, they wouldn't all leak at the same time. They feel it's probably a computer control problem involving the amount of fuel injected........we'll see what happens next.