I just acquired my 4th Mercedes. It is a '91 420SEL with 130,000 miles. As with the first three, this one came to me in inoperable condition.
What I have discovered is that fuel is reaching the fuel distributor, but not making it to the cylinders. So my question is what controls the fuel distributor? Is it the ECU?

If it is the ECU (or similar) that is suspect, is there a way to test it short of a swap out? (I'm assuming that the ECUs from my '89 300SEL, or either of my 190Es would not fit).

Thanks.
-Brett

check the injector and see to it that fuel gets thru if not you might need to change the injectors, normally on a high milage vehicle the fuel distributor should be bad, its not electronically controlled its the old reliable mechanical parts thru cable control

Thanks for the knowledge. I just checked the plenum air flap. Yes it depresses easily and smoothly, and returns to the closed position in a gentle, but definite manner. I had my wife crank the engine so I could watch the flap. Nothing happened on cranking. But when I manually depressed it, as she was cranking, fuel flowed to the injectors (I had one injector line disconnected so I could monitor fuel flow). So fuel doesn't seem to be the problem (although I did not check to make sure the injectors were letting fuel through).

But - I noticed that the engine is cranking unusually slowly. The battery is fully charged and known to be good (it tested as "good" also on a load tester). But the engine doesn't turn very quickly at all on cranking. So now I'm wondering if that could be my problem. And if so, what would cause that? A failing starter maybe?

-Brett

Yes, very nice spark. The engine hasn't turned over at normal speed since I got it (which was just yesterday).

Yeah they are nice cars. My wife doesn't quite understand my MB collection. She says it's a sickness. I just tell her that I'm in good company with this illness.

-Brett

The car was donated to charity and sold at an auction (where I picked it up) so I don't have any history at all.

I didn't notice anything odd about the left valve cover, but I'll take a closer look. I'll probably pull it off to see if I can see anything going on with the chain or rail and let you know.

Thanks.
-Brett

I took the left valve cover off and did find a broken plastic piece. This is unfamiliar territory for me, so I've attached some pictures and am hoping to get some thoughts as to what is being shown. If the pictures don't come through or are too small, here are links to the full-size images.
www.tobogganhill.com/420sel/420_rail.jpg
www.tobogganhill.com/420sel/420_rail2.jpg
www.tobogganhill.com/420sel/420_rail3.jpg
www.tobogganhill.com/420sel/420_plastic_piece.jpg

I look forward to opinions about whether this is worth further investigation or if it is clear that valve damage (or worse) is likely.

The timing chain is loose, but didn't seem horrible (maybe 3/8 to 1/2 inch of play - or maybe that is horrible :-).


-Brett

Attached Thumbnails

       

You have the dreaded broken chain guides. You need to replace them and the chain before you try to start the engine. The guides shed pieces into the running chain and cause the valve timing to move then the real damage happens as the pistons start hitting valves. How about the other side? Are any of them broken?

You need the 3 guides, chain and the tensioner rail replaced pronto.

__________________
I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

Thanks. Now I just need to figure out if it is worth fixing or not.

Because this started as what I thought was a fuel-related issue (and titled such) I just started it as a new thread with the title " 420SEL-assessing timing interference damage ...". In that thread I asked if there is any way to determine the severity of the damage (short of pulling the heads) prior to replacing the chain and guides.

Thanks again.
-Brett

I am not saying that the engine is damaged. In fact it my not be. I had a situation where the broken piece was lodged in the engine and there was no damage. If the engine ran the timing has not jumped. Just replace the parts before trying to start it. Dont assume the engine has bent valves etc.

__________________
I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

Since you already have the valve cover off see if the exhaust valve rockers are loose. If the rockers are loose you have bent valves.
Turn the engine by hand to TDC #1 and check alignment of the cam timing marks (the passenger side cam is usually a couple degrees late but not a full tooth off)
If the drivers side cam is late theres work to do!
Mike