No Spark!

[Skitzerow]

Well I am at thoughts end.  I have no spark.  Engine turns over just fine, but no spark.  I was so proud I had the engine running so smooth and then an hour after I just finish a ten mile run, all of a sudden it would not start.  There was one other no start moment a week ago, but started again.

I check condensors which are suppose to be infinite resistance, I guess.

I check the coil on both sides of the high tension lead which measure about 10,000 ohms.

I check the coil through distributor hook up to make sure it was not grounded.

Don't know where else to look.  And I am not sure I have checked all the possibilities.

The only thing that may have caused a problem somewhere, was I was checking RPM with a dwell/Tach meter.  I was going to compare to the other meter I just used.  I put the clamp on the positive side of the coil and grounded out the other end to the body.  As soon as I did that a couple of times the engine started drop RPM.  I wonder if I blew some electronics somewhere.

Any ideas??  Help greatly appreciated.

SDK

[ja17]

Hello SDK,
If you have the factory transistorized ignition it may be faulty. If you have the standard ignition it will be less costly to fix.  I have the factory test procedurures for testing the transistorized and standard ignitions. I can scan the info to you when you tell me what version W113 you have. What year is your car? You can convert or temporarily convert your car to standard ignition if needed. The transistorized ignitions have a fairly weak spark at the points but more intense at the spark plugs. So it may be a little hard to see at times. the factory started putting transistorized ignitions on these cars around 1969.
Spark, fuel and compression are the basic things to check first. Remove the distributor cap turn the ignition on and push the closed points open with a insulated screw driver. You should get a spark! Next put the distributor cap back on and check and make sure the spark is at the spark plugs. I usually have a spare spark plug and connect it to a plug wire end and ground it to the engine. Have someone crank the starter and observe. Next see if you hear the electric fuel pump running. You may want to momentarily hot wire the cold starting valve on the intake to see if the engine comes to life. Let us know what you find and we can steer you in the right direction.

Joe Alexander
Blacklick, Ohio

[Skitzerow]

I have a 1968 280SL with standard points.  The engine is 2.8L straight six.  Four-speed automatic.

Thanks for helping.

quote:Originally posted by ja17

Hello SDK,
If you have the factory transistorized ignition it may be faulty. If you have the standard ignition it will be less costly to fix.  I have the factory test procedurures for testing the transistorized and standard ignitions. I can scan the info to you when you tell me what version W113 you have. What year is your car? You can convert or temporarily convert your car to standard ignition if needed. The transistorized ignitions have a fairly weak spark at the points but more intense at the spark plugs. So it may be a little hard to see at times. the factory started putting transistorized ignitions on these cars around 1969.
Spark, fuel and compression are the basic things to check first. Remove the distributor cap turn the ignition on and push the closed points open with a insulated screw driver. You should get a spark! Next put the distributor cap back on and check and make sure the spark is at the spark plugs. I usually have a spare spark plug and connect it to a plug wire end and ground it to the engine. Have someone crank the starter and observe. Next see if you hear the electric fuel pump running. You may want to momentarily hot wire the cold starting valve on the intake to see if the engine comes to life. Let us know what you find and we can steer you in the right direction.

Joe Alexander
Blacklick, Ohio

SDK

[Malc]

No cracks in the distributor cap?
Rotor arm ok?
All nice and clean, no dust or contamination?
Have you tried taking a plug lead off, then sticking another plug in it, and seeing if it sparks when the engine cranks (hold on the engine somewhere, don't get electocuted!) Does it spark???
Check the low tension side of the coil too they do fail eventually.
Hope this helps
Malc

[Ben]

Is it possible that the distributor has popped up and the rotor arm isn't turning ?

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[Skitzerow]

Don't know will check.  But I know I have no spark from the coil.

quote:Originally posted by Ben

Is it possible that the distributor has popped up and the rotor arm isn't turning ?

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

SDK

[hands_aus]

When I took the cap off my distributor, the carbon probe that touches the top of the rotor fell out because it was broken.
Could this have happened on your car?


Bob (Brisbane,Australia)
early 250 SL, RHD

[Naj ✝︎]

Make sure the power does not go to ground where the wire fits to the distributir (dizzy ?) from the coil. Easily happens when fiddling with the dizzy!
naj

'Kloines Scheisserle'
65 230SL
68 280SL

[Benz Dr.]

I just did a distributor rebiuld and when I put it back on the engine it wouldn't start or run. It was running Ok before I took it apart and it worked perfectly on the tester I have so I put a different condensor on it and it fired up right away.
It was hitting a bit before that and trying to start but there was no way it would work. I'd also look at the balast resistor. Use a test light to make sure you have 12 volts coming to the coil. I think these cars have a relay and separate wire that will bypass the resistor while starting so you get full battery voltage while starting. No current means no spark. The light will be much dimmer with the resistor in place but you can hook the wire directly on to the coil for testing to see if that's the problem.
If you remove the cap and open the points with a screw driver you should see a spark there if you have power going in.

NOTE:  I always pull number 4 fuse going to the fuel pump while doing things like setting valves , compression testing and testing for spark. You will be dumping a lot of unburned fuel into the engine otherwise.

Dan c

Daniel G Caron

[n/a]

I am experiencing the same "no spark" problem with my 71 280 SL. I have measured voltage at the distributor. It looks normal with the points closed but shows a small voltage (between 1 and 2) with the points open. Same result with I isolated the condenser from the circuit. Manual indicates that voltage should be zero with the points open.
Does the non-zero voltage suggest a problem with the transistorized unit?

[ja17]

Hello SDK and Frank,

Frank, on the non transistorized ignition cars, make sure the small forked wire end  of the points does not rotate and touch the breaker plate in the distributor or the ignition will be shorted out. Next remove the wire from the coil at the 7mm nuted lug on the distributor. If you have voltage at this disconnected wire  with the ignition on, you probably have bad or incorrectly installed points. If the poins are ok the condensor, rotor or cap may be faulty.

SDK, on factory transistorized ignition cars, the points can oxidize or tarnish while in storage preventing spark. The points will look good but will not spark! Remove them and clean or replace. Points are fairly  inexpensive and a good place to start! Be sure to check the ballast resistor as Dan has mentioned.

SDK on the factory transistorized ignitions, a voltage test can be performed to test these units. The ignition points must be OPEN to conduct this test! First switch on the ignition. hook one lead of a voltmeter to ground. Next test both leads of the 0.4 ohm resistor. In both cases reading should be battery voltage. If there is a reading at one side and zero at the other,  then the 0.4 ohm resistor is defective. If there is a difference of about 3 volts between these readings, switching unit (Transistor Box) is defective. Next connect the red wire of the voltmeter to the 0.6 ohm resistor wire which leads to terminal #16 of the switching unit (Transistor Box). The reading should be zero volts. If there is any reading, the switching unit is defective. Remember that the points must be open for the above test*. (*Mercedes Factory Service Bulletin Aug. 1971)

An additional check on the switching unit (transistor box) can be run with the points CLOSED. connect the voltmeter to ground and the red wire to terminal #15 of the ignition coil. Switch on the ingintion and read the voltage on the meter. The reading should be 2.6 to 3.5 volts. Open the breaker points and the voltage must return to Zero*. (*Mercedes Technical Training literature Feb. 67).

Joe Alexander
Blacklick, Ohio

[n/a]

quote:Originally posted by ja17

Hello SDK and Frank,

Frank, on the non transistorized ignition cars, make sure the small forked wire end  of the points does not rotate and touch the breaker plate in the distributor or the ignition will be shorted out. Next remove the wire from the coil at the 7mm nuted lug on the distributor. If you have voltage at this disconnected wire  with the ignition on, you probably have bad or incorrectly installed points. If the poins are ok the condensor, rotor or cap may be faulty.

SDK, on factory transistorized ignition cars, the points can oxidize or tarnish while in storage preventing spark. The points will look good but will not spark! Remove them and clean or replace. Points are fairly  inexpensive and a good place to start! Be sure to check the ballast resistor as Dan has mentioned.

SDK on the factory transistorized ignitions, a voltage test can be performed to test these units. The ignition points must be OPEN to conduct this test! First switch on the ignition. hook one lead of a voltmeter to ground. Next test both leads of the 0.4 ohm resistor. In both cases reading should be battery voltage. If there is a reading at one side and zero at the other,  then the 0.4 ohm resistor is defective. If there is a difference of about 3 volts between these readings, switching unit (Transistor Box) is defective. Next connect the red wire of the voltmeter to the 0.6 ohm resistor wire which leads to terminal #16 of the switching unit (Transistor Box). The reading should be zero volts. If there is any reading, the switching unit is defective. Remember that the points must be open for the above test*. (*Mercedes Factory Service Bulletin Aug. 1971)

An additional check on the switching unit (transistor box) can be run with the points CLOSED. connect the voltmeter to ground and the red wire to terminal #15 of the ignition coil. Switch on the ingintion and read the voltage on the meter. The reading should be 2.6 to 3.5 volts. Open the breaker points and the voltage must return to Zero*. (*Mercedes Technical Training literature Feb. 67).

Joe Alexander
Blacklick, Ohio

[n/a]

JA17,

Thanks for your reply to my "no Spark" question. You have provided the answer that my manual did not address - - the significance of a non-zero voltage when the points are open in a transistorized ignition.