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1975 280SLC
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45 Posts
Discussion Starter #1
Replacing injection with carbs.
All the high pressure system removed. Low pressure pump fitted ( 8 to 10 psi ) pressure regulator to get required 2psi at carbs fitted.
Question.( s )
Fuel return line block it or fit a connection to the system so it's still in use and where?
Between pump and regulator or between regulator and carbs with a plug that has a 1 or 2mm hole through it to act as a flow restrictor???????
 

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1975 280SLC
Joined
45 Posts
Discussion Starter #2
Surprised no-one has come back to me.
Maybe the weekend warriors will will help.
馃槅
 

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1974 450 SLC
Joined
12 Posts
Not much of a weekend warrior, but I'm curious about your SLC. I have a '74 myself and I find the D-Jet fuel injection system to be a bit sluggish. It works, but I wouldn't say it works well. I might get 12-14 mpg highway on a good day. Did you ever consider running the MegaSquirt II EFI system? I've been tempted by it, but it seems like an intimidating project especially since the car is running adequately. What sort of carbs are you using?
 

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1975 280SLC
Joined
45 Posts
Discussion Starter #4
It's a long story. Started with a hole in the passenger firewall.
I've had the beast for about 20 years and it became an addiction on the lines of 'you won't beat me' 馃槰.
The model I have was born in 75 and to cut a long story short just became a bad habit.
Back to bare shell blasted reprimed lots of panels replaced blah blah blah.
The K-jetronic just started dumping all the fuel in the tank everywhere so I decided to just go all the way and scrap it and replace with 3 weber 38DCOES.
I live in Thailand and getting merc parts for anything older than 5 years is impossible. Import tax can be 100 to 300% so you can work out cost, shipping plus tax.
Got the new webers from UK through friends ( they're not chines copies ) and the whole thing is just a project for retirement.
I'll post photos later on.
Tbanks for answering. 馃槅
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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Replacing injection with carbs.
All the high pressure system removed. Low pressure pump fitted ( 8 to 10 psi ) pressure regulator to get required 2psi at carbs fitted.
Question.( s )
Fuel return line block it or fit a connection to the system so it's still in use and where?
Between pump and regulator or between regulator and carbs with a plug that has a 1 or 2mm hole through it to act as a flow restrictor???????
It may depend on the pump, but I would have thought that you would go from pump to a bypass pressure regulator that has outlet to carbs plus a return line to tank. The pump likely has more capacity than you need. Found this diagram for such a system (it shows internal tank pump, but should be same for external pump.


Regarding lack of response - I don't think many here have gone to carbs! I do seem to recall someone going to TBI. But you already have carbs, so you may be on your own ;)
PS: Not on a 107, but here is a guy going from carbs to TBI: http://www.peachparts.com/shopforum/vintage-mercedes-forum/238292-m115-t-b-i-conversion.html
 

Registered
1975 280SLC
Joined
45 Posts
Discussion Starter #7
It may depend on the pump, but I would have thought that you would go from pump to a bypass pressure regulator that has outlet to carbs plus a return line to tank. The pump likely has more capacity than you need. Found this diagram for such a system (it shows internal tank pump, but should be same for external pump.


Regarding lack of response - I don't think many here have gone to carbs! I do seem to recall someone going to TBI. But you already have carbs, so you may be on your own ;)
PS: Not on a 107, but here is a guy going from carbs to TBI: http://www.peachparts.com/shopforum/vintage-mercedes-forum/238292-m115-t-b-i-conversion.html

I'm thinking on the lines of a restricted flow line now between the carbs and the return line. Might be a trial and error exercise with 1mm 1.5mm holes in an inline plug to maintain the 2psi at the carbs.
Or similar between the pump and regulator using a T as the regulator doesn't have a dedicated return outlet.
Trying to 'picture' the flows in my head to work out the best idea.
 
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