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Smog check results Passed Except Ignition Timing

Tiny
TTOMAS2424
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  • 1986 MERCEDES BENZ 420SEL
  • 179,332 MILES
Help!I have a 1986 Mercedes Benz 420 SEL with the 4.2 liter V-8First off the vehicle was taken for a smog check all results from the check Passed Except Ignition Timing---Current setting 20 Degrees @ 900 rpm. Spec Setting should be 12 Degrees @ 600 rpm

I was told to start by setting the Crank pulley @ 0 degrees and then set # 1 piston at top dead center I did! And then make sure Dist Rotor Is pointing at # 1 cylinder It was. Loosen the Dist Bolt I did. Start the vehicle and with the timing light check crank pulley marks at that point I got lost.

Please help If you can thank you thomas.
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Monday, February 6th, 2012 AT 6:47 PM

15 Replies

Tiny
RIVERMIKERAT
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Have of the first part of your question was cut off. What are you trying to do?
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Monday, February 6th, 2012 AT 6:51 PM
Tiny
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I'm sorry about that let me start over.
I took my 1986 Mercedes Benz 420 sel 4.2 liter V-8 In for a smog check all checks Passed Except the Ignition Timing result Failed! Tech says that my current Timing was at 20 degrees @ 900 rpm and the Spec Is supposed to be 12 degrees @ 600 rpm. Not sure how the timing changed because I have not had any timing issues before and the car had always pass emissions tests. How do I Return timing to Its original setting. Thank you so much thomas
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Monday, February 6th, 2012 AT 7:30 PM
Tiny
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Ahhh. Tis fairly easy. Rent/borrow a timing light. (Or buy it, they come in handy). My reference shows that ignition timing is electronically set. But:
Disconnect and plug vacuum line to distributor (if so equipped). Connect timing light to power. Connect inductive pickup to #1 plug wire (observe direction of spark). Start engine. Loosen distributor hold down bolt. Point timing light at crank pulley and observe marks. Slowly rotate distributor until timing mark on block lines up with proper timing degree mark on indicator on pulley. Tighten distributor. Connect vacuum line. Check engine RPM on timing light. Locate throttle linkage and idle air adjustment screw. If idle speed is too fast, back screw out slowly until proper speed is reached. If too slow, tighten screw.

Shut engine off. Remove timing light and test drive.
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Monday, February 6th, 2012 AT 8:11 PM
Tiny
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Thank you for the reply. Rivermikerat. I understand all that you say however i'm a little stuck when you say (your words) Disconnect and plug vacuum line to distributor (if so equipped). Can you please tell me where that vacuum line is located exactally if I have one. I took some digital photos for you. Can you see files? Here we go i'm sending some. Thomas

This Is what my carb looks like. I just finished following you instructions and there was no change to vehicle there must be a vacuum line somewhere I just need help finding it. Thanks again I hope you can see the photos I posted.
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Monday, February 6th, 2012 AT 9:37 PM
Tiny
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Hey Thomas. Only one image came through. It's of the Bosch fuel injection fuel distributor. I did a little more research. I don't think your car has a vacuum advance, so don't worry about the vacuum line. I've attached an image if the distributor cap on your car. Yours may be blue or black.
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Monday, February 6th, 2012 AT 10:19 PM
Tiny
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Here are the other photos for 1986 Mercedes Benz 420 sel 4.2 liter v-8 With the timing issue.I took my 1986 Mercedes Benz 420 sel 4.2 liter V-8 In for a smog check all checks Passed Except the Ignition Timing result Failed! Tech says that my current Timing was at 20 degrees @ 900 rpm and the Spec Is supposed to be 12 degrees @ 600 rpm. Not sure how the timing changed because I have not had any timing issues before and the car had always pass emissions tests. How do I Return timing to Its original setting. Thank you so much thomas
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Monday, February 6th, 2012 AT 11:33 PM
Tiny
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First image is the ignition distributor. I've attached a picture of what it looks like from the bottom. On the right, you'll notice an oblong opening in the "wing". This is where the holddown/adjuster bolt is.

The second image is the timing marks you need to look at while setting the timing. The pointer is dead center above 0 (zero).

Hook up the timing light, start the engine, and loosen the holddown/adjuster on the distributor. Point the timing light at the timing marks. SLOWLY turn the distributor while watching the marks. The light will flash every time the #1 plug is fired, allowing you to see where the pointer is in conjunction with the timing gradients on the pulley.

You may want to loosen the adjuster bolt before you start the engine.
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Monday, February 6th, 2012 AT 11:52 PM
Tiny
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Thank you very much.
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Tuesday, February 7th, 2012 AT 12:03 AM
Tiny
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My pleasure. Let me know how it goes.
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Tuesday, February 7th, 2012 AT 12:09 AM
Tiny
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Hi expert mechanics
My Vehicle Is a 1986 Mercedes-Benz 420 sel 4.2 Liter V-8
I was having an Issue with getting the Ignition Timing set so It would pass my Emissions test. I was advised to do an alignment check by setting Crank pulley, #1 Cylinder @TDC and last point Rotor at #1 cylinder. That's all done all check out good. Next thing loosen Dist Bolt start vehicle and move Dist to achieve appropriate timing. (NO) Good Nothing Happened. Found out that this model has NO manual timing adjustment, It is Electronic so that means that other devises work with the ignition system. SO. Does anyone know how to Test or repair or get a cheap Electronic EZL control Module Part# 003 545 9132 thanks thomas Photo added.
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Wednesday, February 8th, 2012 AT 12:45 AM
Tiny
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Thomas, your distributor has an adjustment slider. The electronics control the spark advance while driving.

What the smog tech may have been referring to is to hand turn the engine until the zero and the pointer line up. Then make sure the #1 piston is at the top of its revolution. Then make sure the rotor electrode is under (pointing to) the #1 plug wire tower. Then hand turn the engine until the pointer is lined up with approximately 12 degrees. Then loosen the distributor hold down/adjustment bolt and turn the distributor until the rotor is once again lined up with the #1 tower.

Using the timing light is normally much quicker and easier. The electronic ignition control box should only need to be changed if it doesn't adjust spark advance properly or the engine isn't running.
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Wednesday, February 8th, 2012 AT 1:06 AM
Tiny
TTOMAS2424
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1986 Mercedes-Benz 420sel 4.2 Liter V-8 Is the car.
My Ignition Timing Is Currently at 20 degrees @ 900rpm
My Spec Ignition Timing should be 12 degrees @ 600 rpm.
I tried moving the Dist nothing happen the settings stayed the same. However I pulled the vacuum line from the EZL and the Idle dropped to 750 rpm according to my Tachometer. Is there something I'm missing Help If you can thanks thomas.
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Wednesday, February 8th, 2012 AT 8:00 PM
Tiny
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Do the test with the vacuum line removed and plugged.
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Thursday, February 9th, 2012 AT 4:18 AM
Tiny
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Thanks I will try that again!
I think that the Crank position Sensor has or Is failing what do you think? I say that because I have read reviews from others that aim me towards that area because Its related to ignition timing? Last chance and I'm going to blow this car up :(
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Thursday, February 9th, 2012 AT 4:44 AM
Tiny
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Our reference doesn't show that make, model, and year having a crank sensor.
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Thursday, February 9th, 2012 AT 4:49 AM

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