Diagram: Thermo Time Switch, 4 Pole Relay, Cold Start Valve, Ignition

[rbouch8828]

Oh, by the way, I replaced the CSV solenoid with a new one from Authentic Classics, when the original failed. Perhaps the shine of that part is what you were referring to.

[rbouch8828]

What I need are the gauges and colors of the connecting wires on this diagram:

[lpeterssen]

Another possible culprit are the relay itself.  If you want and have the patience, open them removing the external shell and polish internal contacts at the coil switch

[rbouch8828]

Do you mean at the 4 pole switch, or at the Cold Start Solenoid? I replaced both of those in the past month or so as part of my effort to get to the bottom of my starting issues.

The first problem was a year ago as I was starting out on my way to a car show in New York. Just as I drove onto the Massachusetts Turnpike, the engine quit and refused to restart. I had been planning to take the car up to Gernold Nisius’s place to have him try to find the source of an oil leak, so I had AAA take the car to him to see what the problem was.

He deduced that my Fuel Injection Pump had failed. I had had the pump “rebuilt” by H & R Fuel injection when I had pulled the engine out, so I was surprised that it was the pump, but Gernold told me that Henri had died not long after they had done my pump and that their work had gone downhill. He also told me that after they did my pump their shop burned to the ground with many pumps in it and with some Porches too. He said they had no insurance!

He had a pump he had taken from a car that he said was working so he swapped out my pump for that one and sent mine out to Pacific for a rebuild. I am still waiting to get it back.

Gernold was able to get the car running, but he had a lot of trouble with it. It was very finicky. It would stall, and quit and then it wouldn’t restart.

Eventually, he felt he had it running well and I picked it up just at the end of the summer. I had a little time to drive it and it seemed OK.

Then this spring, I took it out to go for a drive with the Mercedes club and I drove several miles to meet them in Boylston MA. We spent about 45 min. chatting and then we’re ready to leave for our group drive and when I went to start the car, it would not start. Several of the club members were gathered around my open engine bay and the ones standing next to the CSV said they smelled fuel.

I had AAA tow me home and I tried starting again and I could see fuel leaking around the CSV. So I ordered a replacement. I also determined that the Thermo Time Switch was not working. I tried to find an exact replacement but have been unable to. Instead, I have used the one designed for the Porsche as the numbers are not that far off and I understand people have had success making that substitution.

I also determined that the relay in the 4 Pole Relay had failed, so I purchased a new one from Authentic Classics and replaced the old one with that new one a tested it.

Now everything runs, except I get 5 volts at the CSV instead of 12 and based on the schematic so I thought that the best solution would be to replace the old wiring since that is the only part that hasn’t been replaced. This is causing long starts at times.

Do you think that the new relay could have bad contacts already? What do you think about my idea of rewiring the circuit?

Best,
Roland

[lpeterssen]

Dear Roland

I wrote you a long explanation and while consulting some diagrams to be more precise everything wiped away.  So this time I will cut some details.

1. A car restoration is not complete until the full wiring harness and it’s derivated accesories have been serviced and tested.  That means fuse box, relays, switches etc. That is a huge work that I normally perform for all my own cars and for friends.  For pagodas there is also the option to buy new wiring harness which saves you some time, but…… you always have to check the proper working of the peripherals.

2. In all the wiring harnesses I have serviced so far, which are many, the cold start harness portion is always damaged ONLY at the Thermo Time Switch because the heat at which  cables are exposed.

3. The Thermo Time switch is a frequent culprit, and in my cars I replace it for modern style electronic TTS used on W116/126 making the necessary mods in the harness terminals.  I am not a purist fanatic.  I am an engineer and believe in technology and reliability, therefore I use the components which are more reliable.

4. All Bakelite connectors on the engine bay get dirty with the age or it’s terminals get corroded.  Therefore if you are not having 12V at the CSV, I will suggest to start by cleaning and polishing all the bakelite internal terminals which are involved in its correct working.

5. relays can fail, but you could be able to test them outside the vehicle by applying 12V on its terminals 85(-) and 86(+) and see if contact 30 and 87 which is the switched circuit CLOSES. It should have a perfect continuity among these terminals 30/87 when power it’s applied to the coil terminals 85/86.

6. It’s rare to have a big cable that operates intermittent like the ones that feed CSV (+) and FIP ENRICHMENT SELENOID (+) With continuity problems.  This cables have a large gauge, much more than what is really needed. Cross section 2.5mm equal to AWG14.  Nevertheless it’s easy to check if they are damaged by taking a resistance measure between exit terminal 87 of each of the relays already mentioned and the accessory (+) terminal.

7. DEFECTIVE GROUNDS are always a source of problems.have that always in mind.  To have ground post in excess has never killed anybody.  So if you doubt on ground quality, ground directly the accessory that is failing.

Send me a PM IF YOU NEED MORE GUIDANCE.

Best regards
L.peterssen

[rbouch8828]

Thank you very much.

When I did the engine bay I should have replaced the harness. Rhode Island Wiring had them available, but when I looked at mine, it looked ok, so I didn’t bother. Big mistake!