Could you guys give me some advice?I have a 1978 450 SL.About two years ago I picked up a fuel distributor from a 1980's (I think it may have been about a 1985) mercedes.I would like to install it in my '78.It looks the same as my old distributor except it has one extra line on the '80's model.Could I block this one line and install it on my 1978??I'm having problems with rough idle and milage and would like to test with this newer fuel distributor and also this newer distributor is made from aluminum instead of cast.

Where is the extra line? If your '78 lacks closed-loop lambda feedback and the '85 has it, this is probably the difference. The lambda solenoid goes between the control line (center top) and the return line (one of those on the side) but I don't have any idea how it is plumbed into the car on a Benz.

Thanks Matt for your reply....I will take a picture this evening...The way you discribed it that must be the lamba line....I will post a pick Wed morning.

Picture is a thousand words...

I have posted two pictures...The one on the left is the new distributor(I circled the extra outlet it has).The pic on the right is whats on my '78 now.Could I block off the extra port thats in left picture?If needed the part number of the new distributor is 0 438 100 088 with a extra number of 060 and 444.Hope I could use this new distributor to replace my cast iron one...

Attached Thumbnails

   

Well I did the same thing. Got a fd for a 1980 had lambda line to put on my 78 with no lamba line. I like to say it worked but the top fuel line connections were wrong (have you checked yours) not to mention how to plumb it. I suggest you do what I did. Sell the Lamba FD on Ebay (think I made $50 profit) and get the FD with correct number for your car.

Thanks...for you input....I will check the lines..If its a problem I will get rid of the newer FD...

Your symptoms sound just like the ones my '79 450SL was exhibiting, and it wasn't the fuel distributor. It was the Warm up Regulator, or WUR as some call it. It controls the pressure to the fuel distributor, and it was making a very rich idle and had poor mileage due to also running too rich at speed. I took my WUR apart and decided the spring inside had gotten weak, so gave the adjusting screw on it a turn or two, and all the problems disappeared. I notice that Unwired Tools, or whatever their name is sells an adjustable WUR that sounds like the best fix for the problem. I think you should check the pressure on the line between the WUR and the fuel distributor - it will tell you whether to suspect the WUR or the distributor.

__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C

Thanks Richard.....It been a good 4 years since I worked on my Merc.Knew the car inside out then got into performance tuning of a Cummins diesel.Now I forgot a whole bunch.I know that I did replace the Warm up Regulator and I can't remember the pressure.I will have to start again from the beginning.I know that when I picked the car up in 1996,it was not driven for 4 years.I guess these cast iron FD tend to rust inside when not driven.I still get a slight miss when idling and have adjusted the fuel screw several times.Going to pull the CIS pressure gauge and start testing again.