SU carb improvement - Mercedes-Benz Forum

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post #1 of 1 (permalink) Old 10-17-2008, 09:18 AM Thread Starter
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Date registered: Jul 2008
Vehicle: 1971 Mercedes 280sel (w108)
Location: Nixa Missouri USA
Posts: 86
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SU carb improvement

I've talked of the carb setup I have, but I just made some improvements that really are coming in handy in this cooler weather. I have a 1971 280sel, with a m130 long six. It originally had mechanical fuel injection. That was replaced with a SU side-draft carburettor in place of the throttle body on the fuel injection intake manifold.
Problem was that once the weather started getting colder, it was really getting almost impossible to start. This is a variable choke carb, but I had no way of fuel enrichment or fast idle for cold starts.
First was the fast idle. I used the throttle level solenoid that engages to compensate for the A/C. Now with a flick of the switch, I have fast idle.
Of course this didn't help the car start. I needed fuel enrichment for the initial cold start. The carb had nothing I could use to increase fuel supply. Then I got to looking at the funny round disk on the side of the intake manifold. I'm sure most of you know what this is, but I didn't. Then I found it in my Haynes repair guide. Sure enough, "cold start solenoid". I removed this from the intake, hooked my fuel line to it, ran a temporary hot line to the top of the solenoid, and there ya go a nice fine fuel spray. So I spliced my fuel line inserted a "T" and ran a line.
This morning was 36 degrees F. The car started right up first try. That sure beat the hell out of the 5 minutes of cranking and pumping that I had to do on this car just 2 days ago. I did think I was going to try to put the fuel system back to original, but ginen the cost involved and the fact that I am really enjoying this strange and unique setup, I think I'll just keep what I got.
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