fuelproblem??? Mercedes 560 SEL shuts down after starting while idling, sometimes while driving

I have been experiencing a similar problem on my 1990 560 SEL. After I run for awhile (25 miles or so), the engine will suddenly lose power and stall. I have to pull over, put in park, and restart - which it does without problem. Going down busier roads, I purposely will be in the right hand lane as it will happen intermittently. Seems to run fine otherwise. Fuel is good. Spark must be good. Air is good. I paid $30 for an on-line answer and the guy told me it was a faulty crankshaft position sensor. Ordered that part and the local garage guy couldn't fine where to put it in. Talked to another guy who works on Mercedes and he thought that wouldn't be the problem but might be more relay related. I think he meant fuel related. But I don't why a relay would "behave" again when I can restart moments after it might have overheated. Returned the sensor. I ordered a manual to try to do more troubleshooting on my own but due to the paucity of responses to this problem - I wonder if it is unique to age/mileage and if it is limited to a declining population of models. My car has about 179,000 miles and I had plugs, wires, distributor, fuel filter, air filter, all changed out in a major service several thousand miles ago. Anybody got any ideas?

it has a fuel shut off switch in the trunk,it may be going bad,have it replaced.

My problem was the fuel pumps. One was bad and the other was on its way out.

My '89 560 SEL had problem starting when hot. It would start again after sitting for a while. I took it to a Mercedes mechanic who put in a new fuel pump relay which solved my problem. W.T.

Fuel Pump Relay is most likely and most common cause. So much so that I carry a spare in the trunk ! Same is true for 500SEL series (had one of those also)

There are a multitude of possibilities. The most common issues dealing with stalling on these vehicles is fuel related. But you have to correctly determine what isn't working when it happens. Like this 1986 420SEL I'm working on... This car cranks & runs fine, may run for an hour or maybe only 15 minutes. When the problem occurs, it behaves as if it is running out of fuel... So a fuel psi guage was installed to determine if fuel psi was correct. The guage remained at 98 psi throughout the stalling out process, then when the engine was completely dead, the fuel psi dropped to 45 psi, which is normal. Thus proving that electrically the fuel system on this car in not failing (which includes fuel cut off switches, relays, pumps etc...) All must be well with the electrical/fuel related components. So the engine will start right back up & run for an unpredicted amount of time then it happens again. Most likely cause of failure (since I'm NOT loosing spark either) are the o-rings inside the fuel distributor going bad. This part is located right on top of the engine under the air filter housing, has all the fuel lines running to it. This component can be removed, taken apart, inspected, rebuilt (new o-rings) then reinstalled, or replaced if you find that bad gas has damaged internal components that o-rings can't fix. Such high psi fuel system would make it easy for deteriorating O-rings to be pushed/manipulated out of their normal seating area by the high psi and allowing the fuel to bleed off instead of going to its proper destination, then when the engine dies and the high fuel psi isn't on the system anymore, allows the o-rings to relax back into position to allow the vehicle to run again. (HOPE THIS HELPS ANYONE WHO'S LOOKING FOR ANSWERS) If you determine this be the cause of your stalling/no start, there is an O-ring/rebuilt kit available for this through mercedes-benz or you can even check ebay, type in fuel distributor and see prices ranging from $650-$1000 for a reman fuel distributor or around $90 for the well explained o-ring kit...

Thanks for continuing this thread. I still have my 560 SEL (now on to body work). Put a pile of money into this car, but I do love it. Suspension system, alternator, starter motor, hoses, door hinge mechanisms so they close smooth, etc. I must be nuts. I sometimes think about getting another car like it with a good body/engine/transmission and using this one to feed it parts, but that would put my marriage at risk.

I have a 1995 320e Wagon. I love the hell out of it and i had these fuel issues from fuel pump to relay amd it stalling on me at any unpredicted moments i ended up replacing the wire harness and it ran again. But i parked itfor a year and went to start it it started right up and as soon as the fuel that was in the fuel line ran out the car stalled and i dont hear the pump so i just bought the forth one in 5 years i guess it must be the cheap gas. I even bought a mas sensor and ais sensor since i was curious and broke them on accident. Now i hope everything will run smoothly when I completel this process. Wish me luck.

My fuel problem is alittle different when cold it takes three attempts to start it. It always rough idles at times i smell gas. On the street theres a miss burns alot of gas, on the freeway runs like a charm im leaning towards injectors. Any advice?

Finding my 86 560sel, just purchased from friend, fuel delivery issue root cause was contaminated gas. Car sat garaged for extended time. Replaced pumps and filter, and then replacement pumps failed... contaminated debris damaged and not warranted. Repair shop spent 5 hours flushing and finally found the sock or screen that goes inside the tank was broken, no screen/clogged. So replaced sock, ran like champ but then new sock clogged again. Currently removing/cleaning hoping the debris has now cycled out. So frustrating.

Stevelove1954@gmail.com

I believe I have the solution to you'll problem, change the Idol control valve,which is located in front of the motor, I also owe a 1986 W126 Sel Mercedes northernflavor@aol.com

Everyone please make sure your fuel hose that runs on the top of the engine bay under the air filter housing is not cracked and leaking. I have discovered 2 cracks in both the fuel hoses, and believe that's where the fuel smell is coming from!!!!!!

I drive a 1991 Mercedes 560 SEL. I had the same problem with it simpy shutting down on several occasions without warning within a few blocks. I had it towed to my mechanics. They replaced the Fuel Pump Relay & the OVR relay. Runs perfectly again.

I have a 1990 560 SEL with 200,000 miles. I bought from a guy who was running regular unleaded (requires premium) while adding tons of cheap fuel additives (like STP from auto zone and O'Reillys) just to save money. When I got It home (just barely) I flushed the fuel tank, Changed the fuel filter, disconnected the fuel lines under the hood and to the filters and let it drain for about a week. I then put everything together and filled it with premium gas and added a bottle of B&G fuel additive available only from my mechanic (about $20). I swear by this stuff in my other older cars. The car ran perfect. Last week I bought a new air filter for it and the smaller filter that also fits in the filter housing and goes into the air intake opening. I filled the tank with Chevron super premium (the most expensive gas available, I though more would be better) and guess what happened. It started stalling again. I wondered whether this particular year, make and model required a super specific octane level of gas. Has anyone ever tried using the super premium gas in their older 560 SEL?

Hi i am victor driving a 500sec when its cold it run smooth for an hour but once its hot it decline the speed what might be the cause.

I had that problem and it turned out to be the ignition coils.

These Benz's are only suppose to run on non-ethanol gas. Ethanol is usually what deteriorates the fuel distributor o-rings.

I agree on the Ethanol Fuel Problems. My 1991 560SEL had been sitting for a few years when I bought it, it ran great for about a year, and the fuel system slowly started to die, which is where it stands currently. I have taken the EHA valve off, and the condition of the o-rings (only on the INSIDE of the orings) is cracked/deteriorated, the outside of the orings still looks new (the part not exposed to fuel) so this seems to be proof positive that the fuel is causing the problem. Same thing is happening to all other fuel related parts, and replacement is getting frustrating and expensive! Where can you buy gasoline without the bloody ETHANOL in it??

Chevron 94 octane (in Canada) has no ethanol in it. Some union76 have fuel without ethanol.

This was exactly what happened to my 500SL Most likely cause of failure (since I'm NOT loosing spark either) are the o-rings inside the fuel distributor going bad. This part is located right on top of the engine under the air filter housing, has all the fuel lines running to it. This component can be removed, taken apart, inspected, rebuilt (new o-rings) then reinstalled, or replaced if you find that bad gas has damaged internal components that o-rings can't fix. Such high psi fuel system would make it easy for deteriorating O-rings to be pushed/manipulated out of their normal seating area by the high psi and allowing the fuel to bleed off instead of going to its proper destination, then when the engine dies and the high fuel psi isn't on the system anymore, allows the o-rings to relax back into position to allow the vehicle to run again. (HOPE THIS HELPS ANYONE WHO'S LOOKING FOR ANSWERS) If you determine this be the cause of your stalling/no start, there is an O-ring/rebuilt kit available for this through mercedes- benz or you can even check ebay, type in fuel distributor and see prices ranging from $650-$1000 for a reman fuel distributor or around $90 for the well explained o-ring kit... For a quick-fix/diagnostic we poured about 8 oz of brake fluid into an tank at about 1/3 to empty and let the car idle so the brake fluid re-lubricates the "o" rings. If this fixes your problem you have definitely bad "o" rings inside your fuel distributor. The brake fluid reconditions/expands them and the car fuel pressure when up to 60psi steady. Before this the fuel pressure was at about 50 psi at start and slowly decreasing to about 40psi and the it will stall..