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Mercedes-Benz engine repair questions and answers

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  • isaiahwalker74
    isaiahwalker74 - 1997 Mercedes Benz E320 - Engine - 11/30/2014
    Will E320 "97" still crank if battery is dead?
    I have a 12v battery charger hooked up and still wont crank.... car has been sitting for months w/out a start
    0 answer
  • Richard
    Richard - 2002 Mercedes Benz C240 - Engine - 11/17/2014
    Fault code cylinder 6 misfire
    have changed injector and swapped coil tested fuel pressure and read supply voltage to injector and coil good
    • Jimm
      11/17/2014 Jimm
      P0306 = Cylinder number 6 misfire detected
      A code P0306 may mean that one or more of the following has happened:
      •Faulty spark plugs or wires (particular to number 6 cylinder)
      •Faulty coil (pack)
      •Faulty oxygen sensor(s)
      •Faulty fuel injector(s)
      •Burned exhaust valve
      •Faulty catalytic converter(s)
      •Stuck/blocked EGR valve / passages
      •Faulty camshaft position sensor
      •Defective computer

      If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

      If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

      Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0306 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.
  • Robert Fulks
    Robert Fulks - 2012 Mercedes Benz E350 - Engine - 11/1/2014
    How do I remove the plastic engine topper so I can access the spark plugs?
    All videos I've seen on the subject indicate that the plastic top on the engine is simply snapped on. Not So!. My car has the piece integrated with the air intake (mass flow sensor and several electrical component) and is bolted to the car. I've found the two bolts ...
    0 answer
  • Shelley
    Shelley - 1988 Mercedes Benz 420SEL - Engine - 10/20/2014
    I installed an injection system on my car before i installed an injection system it was running ok u just smelled gas
    the gas smell was coming from the injection system because gas was coming out the gasket on the injection system now my car wont idle and i have a bad battery will that stop my car from idling ? can u help me?
    0 answer
  • SunnyMoe
    SunnyMoe - 2002 Mercedes Benz S430 - Engine - 10/18/2014
    My car hesitates when I try to accelerate what could be the problem ??
    If I'm at a red light that changes to green when trying to go it doesn't go
    • benz guy 888
      10/18/2014 benz guy 888
      define hesitates? does if feel like its choking or loss of power? i suggest the following: if you have an automatic transmission check the level of the atf, you may need to add some, check your air filter. an old air filter will have problems letting air pass through. you'll have to replace this if it is, check your fuel tank, lines, fuel filter. if there are sediments in the tank, lines,'ll have to get this cleaned. the fuel filter should be replaced. if there is any air in the lines or in the filter, there might be a crack in the o-rings or fuel lines...replace them...hope this helps.
    • Jimm
      10/18/2014 Jimm
      First step - have the stored fault codes or check engine light scanned - for free - at any local auto parts store; Advance Auto, Auto Zone, NAPA. Then, post a reply as 'add answer' with the specific code for more assistance. There may be a fault code stored in the OBD memory which may not be displayed as a check engine light.

      Possible Causes of Engine Hesitation or Stumble:

      Dirty fuel injectors (cleaning the injectors often fixes this)
      Dirty air filter (change filter)
      Dirty / clogged fuel filter (change filter)
      Bad MAP (manifold absolute pressure) sensor
      Bad TPS (throttle position) sensor
      Bad or dirty MAF (mass airflow) sensor
      Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
      Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
      Bad gasoline (fuel contaminated with water or too much alcohol)

      Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

      Dirty or worn spark plugs
      Bad plug wires
      Weak ignition coil
      Wet plug wires
  • Fred
    Fred - 1989 Mercedes Benz 560SL - Engine - 10/18/2014
    My car wont start, its been 5 months i left the engine running till run out of gas. last weekend i put new battery
    replaced fuel filter,changed the following engine oil 20w40, spark plugs, a good amout of gas going to fuel distributor, and good electrical current still engine wont start./fire up. this is 1989 mercedes benz 560sl 84,000 miles. i need some advice.
    • benz guy 888
      10/18/2014 benz guy 888
      there might be some air in the fuel lines and in the filter.
  • Dave
    Dave - 1991 Mercedes Benz 300SE - Engine - 10/18/2014
    Replaced battery, turns over but won't start.
    Car sits for months and battery was dead. Replaced battery, turns over but won't start. I have spark to the plugs, I have fuel to the carb, but not to the injectors.
    • benz guy 888
      10/18/2014 benz guy 888
      check the fuel tank, lines and filter...there might be sediments blocking the flow or the o-rings or lines might have cracks letting air might have to clean the tank and the lines , replace the lines and the filter or all of the above. check the fuel pump too.
  • AutoMD Member
    AutoMD Member - 1996 Mercedes Benz E320 - Engine - 10/18/2014
    Engine cranks but no fuel to engine
    at repair place think it could be a control mod
    • benz guy 888
      10/18/2014 benz guy 888
      let me get this question first...your car wont start because fuel wont flow? You said the engine cranks...but does the starter sounds strong when it cranks? it could be the starter if it doesnt crank all the maybe that you have a weak battery that's why the starter doesnt crank all the you see any leaks in the fuel line? Do you see air in the fuel lines? the o-rings or the lines might be compromised/cracked you may have to change the fuel lines...when was the last time you changed the fuel filter? replace the filter if it is dirty, the fuel cant flow freely if the fuel filter is dirty...lastly was your car in the garage for a long time? the fuel tank may contain sediments that clogs the fuel lines, change the fuel filter and the fuel tank and the fuel lines. hope this helps.
  • clarence davis
    clarence davis - 1989 Mercedes Benz 190E - Engine - 10/18/2014
    How to replace aux fan
    • donnydonnyd
      10/18/2014 donnydonnyd
      It should be a few bolts and unplug
    • Tarikul Islam
      10/18/2014 Tarikul Islam
      Please see auto repair shops
    • Jimm
      10/18/2014 Jimm
      The radiator is very expensive and delicate, and can be easily damaged while working around it. If you are going to be doing other work on the car and/or are worried about damaging your radiator, I recommend you remove it first. It is not a difficult job and can potentially save you a lot of money if you end up damaging it. That being said, you certainly can replace your cooling fan assembly with the radiator in, but I recommend you put a piece of cardboard over it to protect it while working.

      You are going to need to drain the cooling system. There is an access panel on the lower passenger side of the front bumper. This will allow you to get to the radiator drain plug. Remove the panel by pulling straight out on it. This will give you access to the drain plug. Turn it clockwise to drain the system. This plug can sometimes get corroded and break when turning. If you do break it you can replace it, but sometimes it is easier just to undo the lower radiator hose.

      Begin by removing the two rubber hoses on the drivers' side of the car that go from the water pump to the radiator. Next remove the overflow hose from the top of the thermostat housing. Remove the thermostat overflow hose from its clip on the top of the engine, and remove the distributor cover plate. It is just held in by clips and pulls off.

      Next remove the fan shroud. Unclip the circular part of the shroud from the base by removing the circular clip on the right side. Turn the shroud to the right, separating the circular part from the base and place it over the fan. Pry off the two clips connecting the base of the shroud to the radiator, and lift it from the engine compartment.

      Check the various on-line vendors;,,, to list only a few. For example, they (RockAuto) list the radiator fan assembly from around $69.00 for your vehicle.
  • brian
    brian - 1992 Mercedes Benz 300SE - Engine - 10/17/2014
    Engine runs good until it reaches operating temp. Then wont idle.
    over heated replaced head gasket and throttle body. engine has 117000 mi. Symtoms were present before over heating.
    0 answer
  • mrT
    mrT - 1989 Mercedes Benz 560SEL - Engine - 10/9/2014
    Change engine now car wontstart1989mercedesbenz560sel
    it started at first then after we started working on vacum holes try to restart car seem it wasnt getting spark to start engine
  • gsinger1979
    gsinger1979 - 1999 Mercedes Benz C230 - Engine - 10/6/2014
    My car did not passed smog. The fuel sensor was replaced. The diagnostic tool reads a yellow light
    My mechanic lent me a diagnostic tool and said do not take it to get it smogged because it will take a bit for the codes to clear. It has been 5 days. How much more should I have to drive it until the diagnostic tool gives me a green light. It is yellow now.
    • Jimm
      10/6/2014 Jimm
      The check engine light is located on the dash and stays on if the computerized engine control system detects an engine performance or emissions problem.

      First step - have the stored fault codes or check engine light scanned - for free - at any local auto parts store; Advance Auto, Auto Zone, NAPA, etc. Then, post a reply as 'add answer' with the specific code for more assistance. There may be a fault code stored in the OBD memory which may not be displayed as a check engine light. There are literally hundreds of possible fault codes and therefore numerous reasons for the MIL condition.

      This step is important - retrieving the stored fault code and relaying this detail - will provide good information to assist in diagnosing and repairing the issue you are having.
      12/9/2014 Tom
      I have similar issue with codes p0455, p0456 and p0303
  • tee94MBNZE20
    tee94MBNZE20 - 1994 Mercedes Benz E320 - Engine - 9/21/2014
    I have replaced fuel pump, crankshaft position sensor, etc. and my car still will not start. Help???
    Car will turn over but not crank.
    0 answer
  • PC
    PC - 1995 Mercedes Benz S320 - Engine - 9/9/2014
    After driving my car for about an hour, when I turn it off, I have to wait about an hour before it will start again
    Once the car starts , it runs fine. I caint figure out what is causing this delay in starting. When inturn the key, there is no sound. This has happen on 3 different occasions. The starter, alternator, and battery checks out This started after I drove through ...
    • AutoMD Member
      9/9/2014 AutoMD Member
      You'd better use a professional person Benz diagnostic tool, so relatively safe, of course, if you believe that you can solve the problem yourself, or consult a professional mechanic.MB SD Connect Compact 4 support reading out & erasing trouble code,reading the real-time data of sensor and actuator, coding and programming. Also support wireless diagnose, support K line,CAN BUS and UDS protocol, with multi-language.hope it is helpful to you.
  • tee94MBNZE20
    tee94MBNZE20 - 1994 Mercedes Benz E320 - Engine - 9/5/2014
    What would cause my car to shut down while driving? and now it won't start,
    Driving at about 55 mph, car cut off. Would not restart. Could this be the fuel pump?
    • Alex Merlin
      9/5/2014 Alex Merlin
      You'd better use the BENZ diagnostic tool to diagnose if you are sure that you can solve it by yourself, or you can also consult a professional mechanic. The MB STAR system, when it made its debut, was much more capable because it was PC-based (IBM T30 laptop), but it was also very versatile

      because it incorporated a HHT emulation mode (for backward compatibility) along with a "multiplexer" intermediate unit between the PC and the car,

      which allowed the connection of a variety of different diagnostic connection cables, depending on which diagnostic system the car in question happened

      to use. For the oldest cars (i.e. the C126, early R129 SL models, early W124s and W140s, etc.) a "four-pin" diagnostic cable was provided. For second-

      generation cars, such as the E500E, 400E/E420, middle and later R129s, middle and later W140s, the familiar "38-pin" plug is provided. There are also

      OBD-2 interface cables for model year 1996 and later cars, as well as a 14-pin cable for European diagnostic systems. All of these cables allow the

      combination of the MB STAR with the in-line multiplexer unit to fully interface with any particular car's computers.The below website may be helpful for you to find the tool. hope it is helpful to you.