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Thread: 1994 E420 engine dies / hard to start

  1. #1
    Junior Member
    Join Date
    Aug 2018

    1994 E420 engine dies / hard to start

    Hi, I'm new here and new to the world of Mercedes. I have picked up a 1994 E420 with way too many miles in hopes of extending it's life a bit. The car ran and drove at the time of purchase. However now I'm having difficult time starting the car, and the car idles rough and cuts out. Sometimes not restarting. It does drive very short distances but at this point i would not call it driveable... the engine cuts out every 50 feet and is nearly impossible to restart. I was hoping to get some help in narrowing down the problem.

    What I have done so far.

    I have checked fuel pressure and spark. The wiring harness has been replaced and has an 07 date code. I did try swapping the camshaft position sensor to a known good one, but that did not help.

    I have the following fault codes and they do not clear:

    004, Post
    4 Voltage at air mass sensor with hot wire.

    Voltage too large/small or ground cable at air mass sensor
    open circuit. (The fault may be ignored on vehicles up to 07/91)
    Verify voltage at air mass sensor with hot wire.
    While IGNITION=ON = 1,0-1,2 V - ENGINE=IDELING = 1,3-1,7 V.
    Verify also the ground cable for sensor. (While IGNITION=OFF < 6 Ohm)

    __________________________________________________ ___________
    007, Post
    7 TN incorrect or open circuit/short circuit.

    Verify the TN input signal voltage.
    While ENGINE=START or ENGINE=IDLING, voltage = 5-7,5 V.
    __________________________________________________ ___________
    008, Post
    8 Signal from camshaft position sensor open circuit/short circuit.

    Verify position sensor voltage.
    While ENGINE=START or ENGINE=IDLING, voltage = 0,8-1,8 V A.C.
    __________________________________________________ ___________
    009, Post
    9 No starter signal at terminal 50 open circuit/short circuit.

    Verify starter terminal 50 voltage.
    While ENGINE=START, voltage = 11-14 V (during start).

    According to the troubleshooting manual the possible cause of the fault codes are:

    004 wiring, n3/1 (lh-sfi), w11 (ground), b2.2 (maf)
    007 wiring, n1/3 (DI control module), n3/1 (lh-sfi)
    008 wiring, l5/1 (CMP sensor), n1/3 (DI control module)
    009 wiring

    Thank you for your help.

    UPDATE #1: I found a blown fuse F2 on the base module (N16/1). Currently have codes 007 and 009 left. The car is much more eager to start. I have not tried driving it but it still doesn't appear to be running right.
    Last edited by benzfiend; 08-23-2018 at 01:30 AM.

  2. #2
    Site Honcho
    Ich bekenne mich
    nicht schuldig.
    gerryvz's Avatar
    Join Date
    Nov 2008
    Annapolis, MD

    Re: 1994 E420 engine dies / hard to start

    I dunno folks ... should we allow him access to the secret sauce ...?

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