1974 450SEL D-JET - Failed Pertronix attempted, restored points, now no start

[chinny4290]

Hi All!

I summon the wonderful and resourceful minds of you all to help me with my 1974 450SEL.

I attempted to fit the Pertronix II Ignitor while retaining the stock switch gear (Ignition Control Unit) as POINTS REPLACEMENT. I have not by-passed ICU with Flamethrower COIL.

Prior to the attempt, the car ran pretty decently with stock points. It was typically missing below 2K which meant to me that the points needed replacing. I said screw it and went with the Pertronix.

This is what I did.

ATTEMPT ONE: Installed Pertronix into Distributor. Followed instructions that came with the box, connected both PERTRONIX leads to a brand new OEM Bosch Ignition Coil.

Result: CAR RAN AMAZING. It literally felt like it was the best thing I did.
Problem 1: Tachometer stopped working.

I also realized I forgot to add a DISTRIBUTOR GROUND WIRE from the distributor to the NEGATIVE BATTERY LEAD.

So I parked the car and removed the Battery over night to tackle the project the next day (it got dark out).

(Car drove fine for 25 minutes around town).

In Between Attempts:
I went and spent a good two hours searching and reading for Pertronix install information here and other Merc forums.

Found these to fix my Tach:

(LINK 1) - http://www.peachparts.com/shopforum/vintage-mercedes/232580-pertronix-install-early-107s-working-tach.html

(LINK 2) - Pertronix install - 1975 450SL - Mercedes-Benz Forum

(LINK 3) - Pertronix Install with and without Switchgear - Mercedes-Benz Forum

ATTEMPT TWO:

I followed LINK 3 to the T and this is what I did:


And THIS IS WHAT HAPPENED (RESULT in VIDEO) -

https://youtu.be/_7QgUdmIUnA



FALLBACK ATTEMPT: To see if the car still ran I replaced the points and the Green Point wire from ICU and now the car won't start PERIOD.


QUESTIONS:

Question 1 - Did I Fry the Pertronix unit by accident?
Question 2 - Did I try the ICU unit by accident?
Question 3 - Did I fry both by accident?
Question 4 - Is there a chance I flooded the engine from the failed Ignition?

Other - Fuel system is fine. Fuel pump runs when you turn the key and try to start.


PLease help guys! I was just so happy when the car ran beautifully. Now I'm really bummed the car isn't running at all!

[tyl604]

Sounds like it is flooded.

[chinny4290]

That's what I figured.

Removing the spark plugs and letting it sit over night should suffice??

Also, any idea in why the Second attempt for the Pertronix didn't work for me?

[Graham]

That green wire in second pic. Is that the wire from the distributor points? If so, it goes direct to the switchgear. On the diagrams you used, the green wire went to terminal where you attached the black wire and that was correct for car wired that way. So we need to look at wiring diagrams with later switchgear and determine where the black wire can be easily connected so it goes to same place as the points green wire. OK, according to attached diagram below, the black wire from Pertronix should go to center pin of terminal 7 of the switchgear on your W116.

The Pertronix II info says it must not be used with the original copper cored plug wires. Link III says to use model 1885, the original Pertronix Ignitor that does work with copper cored wires. It can be burned out if the key is left on with distributor in just the wrong position (does not happen in normal iuse). Pert II apparently protects itself against this. But just how, I don't know. No experience with it. Maybe you could swap Ignitor II for an Ignitor I?

First step is to get car running again with points. Make sure points are set properly - A gap of 0.014" is a good start (should be checked with dwell meter)

[chinny4290]

Hi Graham! Thank you for replying ( I was hoping you would, seeing as you seem like the resident Pertronix expert )

So it ended up being a flooded engine (sorry for the dramatic post, I was freaking out wondering if I did some serious electrical damage to the car, thankfully I did not).

I removed the plugs and cranked the motor with the starter to clear the cylinders, and I got the car working with points again (like ****, but thats because I probably messed up the dwell angle).

Originally Posted by Graham

That green wire in second pic. Is that the wire from the distributor points? If so, it goes direct to the switchgear. On the diagrams you used, the green wire went to terminal where you attached the black wire and that was correct for car wired that way. So we need to look at wiring diagrams with later switchgear and determine where the black wire can be easily connected so it goes to same place as the points green wire. OK, according to attached diagram below, the black wire from Pertronix should go to center pin of terminal 7 of the switchgear on your W116.

Regards Pertronix II - I bought the II unit because knowing me, I would leave the ignition on for too long, frying the I unit (just looking after my own self).

In regards to GREEN WIRE - In STATIC Pic one with the captions of where I placed, that's AFTER I replaced the points and reconnected the wire from Ignition Control Unit. It's just an illustrative picture to show how I wired the Pertronix II and it did not work.

In the No Start YouTube Video Clip - that's with the Pertronix II installed, Green Point/ICU wire disconnected, and Pertronix II wired as per the diagrams in the linked threads from other owner attempts.

Originally Posted by Graham

The Pertronix II info says it must not be used with the original copper cored plug wires. Link III says to use model 1885, the original Pertronix Ignitor that does work with copper cored wires. It can be burned out if the key is left on with distributor in just the wrong position (does not happen in normal iuse). Pert II apparently protects itself against this. But just how, I don't know. No experience with it. Maybe you could swap Ignitor II for an Ignitor I?

First step is to get car running again with points. Make sure points are set properly - A gap of 0.014" is a good start (should be checked with dwell meter)

Thank you for verifying the type of original Spark Plug wires. The Spark Plug wires appear to be BOSCH original ( but still in good condition, insulation and connector wise). I could not determine whether the BOSCH High Temp Silicone (as it's labeled) were solid copper core or not.

I have an extra new pair of Karyn/Bremi/STI wires. Should those work with the Pertronix II?

I want to reattempt the PErtronix II. If I rewire again to the diagram using the KARYN wires, it should work?

If I read your reply correctly, I should leave that ICU Green Points Wire and attach that to the Black Pertronix II? I have loop connectors and can easily connect those with a nut/bolt and a lead cover. Or do they have to meet at the Ballast Resistor to make the Tach work?

Thanks again Graham

[meltedpanda]

if you left the key in the on position for any length of time you could have fired it. that aside . Graham is the expert on this forum , I learned from him, not many of us Djet guys left

[chinny4290]

Originally Posted by meltedpanda

if you left the key in the on position for any length of time you could have fired it. that aside . Graham is the expert on this forum , I learned from him, not many of us Djet guys left

I thought the Pertronix II prevented that?

The longest the ignition was on was only for long cranks when the car did not run.

[Graham]

Red should go where you connected it.
Black should go where the green wire now connects. (you can splice black to green if that makes it easier or buy a connector so black wire will plug into the switchgear. The green wire likely has shielding that is grounded at the switchgear, so just keep the black wire from contacting that.

All wire sets designed for these cars have copper core and very low resistance. Pertronix says they should not be used with Pertronix II.

You cannot use solid core (typically copper) spark plug wires with this product. Solid core wires do not suppress electro magnetic interference (EMI) which will interfere with electronics in this product. A suppression style or spiral wound spark plug wires must be used.

To use the Pertronix II, you would need to source a set of non-copper wires. If they have high resistance, then you may also be faced with changing to the higher voltage Flamethrower coil and likely bypassing the switchgear. There are also other issues that would need to be addressed. Some owners have used the Pert II, but I just don't know the details of what they did and how well it worked.

For simple points replacement that you were aiming at, the Pert I works fine with existing plug wires, coil and switchgear. It may best to try and do an exchange , or just stay with points!

[chinny4290]

OK So the car ran for a hot minute when I tried to start it today and then PLOP. dead.....

No spark....I didn't touch anything . Fuel system still goes. Is it possible my ICU just went or would poorly placed Point/Condenser cause a no-start?

I apologize in advance (err....no pun intended LOL) that I'm a complete noob to handling Points and Condenser.

I never touched mine on my 280S because it ran so well after just redoing wires, cap, rotor, coil, and plugs.

Trying to learn as I go!!

Also, I'll most likely just get the Ignitor I