https://images.search.yahoo.com/yhs/search?p=ignition+system+450sl&type=cpds&hspart=att&hsimp=yhs-att_001#id=45&iurl=http%3A%2F%2Fwww.benzworld.org%2Fforums%2Fattachments%2Fw123-e-ce-d-cd-td%2F594697d1381176466-ignition-gurus-pull-m110-ignition.jpg&action=click

https://images.search.yahoo.com/yhs/search?p=ignition+system+450sl&type=cpds&hspart=att&hsimp=yhs-att_001#id=33&iurl=https%3A%2F%2Fwww.sl113.org%2Fwiki%2Fuploads%2FElectrical%2FJHCrane5.png&action=click

https://images.search.yahoo.com/yhs/search;_ylt=AwrVrFdACYBdkCsAqw4PxQt.;_ylu=X3oDMTB0NjZjZzZhBGNvbG8DZ3ExBHBvcwMxBHZ0aWQDBHNlYwNwaXZz?p =ignition+system+450sl&type=cpds_8304_CHW_US&hspart=iba&hsimp=yhs-1&param1=362560936074645023157&param2=eyJ1YSI6Ik1vemlsbGFcLzUuMCAoV2luZG93cyBOVCAxMC4wOyBXaW42NDsgeDY0KSBBcHBsZVdlYktpdFwvNTM3LjM2I ChLSFRNTCwgbGlrZSBHZWNrbykgQ2hyb21lXC83Ni4wLjM4MDkuMTMyIFNhZmFyaVwvNTM3LjM2IiwiaXAiOiIyNjAwOjE3MDA6N DJjMDozNzEwOjRkMmM6ODRiMDozOGYzOjg0YjUiLCJnZW8iOiJ1cyJ9&param3=eyJ2ZXJ0aWNhbCI6InBkZiIsInlpZCI6ImNwZHMiLCJjdGFnIjoiODMwNF9scDM0X3dpdDE1NjQ5MTExMjkiLCJkb21ha W4iOiJ3d3cubXlzYWZlLXJlc3VsdC5jb20iLCJxdWVyeSI6Imlnbml0aW9uIHN5c3RlbSA0NTBzbCIsImdjbGlkIjoiRUFJYUlRb 2JDaE1JOWJhUG52VG80d0lWQ1E3bkNoMkhvQV9fRUFFWUFTQUFFZ0p0bF9EX0J3RSJ9&param4=eyJjIjo4MCwicSI6dHJ1ZX0%3D&ei=UTF-8&fr=yhs-iba-1#id=34&iurl=http%3A%2F%2Fwww.peachparts.com%2Fshopforum%2Fattachments%2Fvintage-mercedes%2F20488d1093147563-transistorized-wiring-diagram-transistorized-wire-diagram.png&action=click

I'd be looking at the green , green / yellow wire running into the distributor. I " think " this system uses am old style contact point arrangement to trigger the ignition module.

Make sure the brown wire at the module is grounded.

There is a thread in the veteran's section about replacing the transistor in the ignition module. It's pretty straight forward with a soldering iron and the part is a few bucks, plus shipping.

The quick test of it is the little green wire at the top of the diagram, hook up a dwell meter to that. Zero dwell while cranking means you have short or a dead box.

BTW, that box must be grounded well; usually the three bolts to the firewall provide that ground. If you snag a replacement box, make sure to actually mount it correctly before firing it up.

-CTH

__________________
- cth350@gmail.com
http://www.111lakeside.com/

Is there a resistance check that can be done on the distributor itself? I have a 78 450sl with a no spark condition aswell! I've done quite a bit of reading and thru some tests I feel I've determined the distributor has failed. But I want to confirm it, just cant find a "test" for it. (I dont have a way to monitor dwell). I have battery voltage to ignition coil with key on, 9v while cranking (which means the ignition switch, ballast resistors and everything up to the ignition coil is good) resistance checks on the coil itself check out (.4 ohm and 10.5 kohm, within spec on both), green wire to dist. is brand new, aswell as cap/rotor/plugs/wires, tested terminals 4 and 5 for voltage at diag port (0v like there should be, meaning switchgear/ignition box is good). Which leaves the distributor..... thoughts?

I can provide more detail on what tests were run to determine all of my findings, but its everything that can be found thru google/prodemand(mitchell)

Any and all help is much appreciated!!

Pull the green wire plug from the ignition box, check for resistance between center pin and the shield. 600+/-100 ohms.
Under what conditions was the green wire renewed? What was the cause? By whom performed?

I am still unable to start the engine after all the above diagnostic procedures. Anyone able to offer any insight please?

9V while cranking is too low. Hav you tried with jumper cables form a running car?

__________________
Prost!