Injection to carbs - PeachParts Mercedes-Benz Forum

andyslc · #1 02-09-2017, 12:22 PM

I will be changing to weber side draughts and getting rid of the D jet system.
I am not concerned about mileage or performance etc.

Do I need to worry about the fuel return line, I don't think I do but would like confirmation.

Once I remove the HP pump filter unit etc from the car what would be the best pump to fit for 3 x 40 DCOE's ? Been told 6 psi.

Thanks in advance

Mike D · #2 02-09-2017, 12:44 PM

I'd use the return line in the system if at all possible. The small lines used in the tank venting system are barely adequate as it is. Without the return line circulating and cooling the fuel you will probably have cabin fume issues.

Frank Reiner · #3 02-09-2017, 03:33 PM

a:

The Webers will require a fuel supply regulated to ~3-5psi. Just upstream (pump side) of the pressure regulator a tee can be installed in the feed line from the pump with a return orifice of 1.2-1.5mm, and then be connected to the existing return line to the tank. This configuration replicates the single package regulator/return connection that was used with some carbureted M110s from 1976 onward, most notably in Sweden.

andyslc · #4 02-09-2017, 07:09 PM

Many thanks.

andyslc · #5 02-17-2017, 12:50 AM

Can anyone give me pen portrait/hand written description, of how the injectors and the top unit with the six connecting tubes to the injectors work.
The injectors have no electrical connection joints so I really have no idea how they work.
I have a photo I will post in a minute or two.
I will allocate two more weeks to the injection then if no go will go for carbs.
😨

andyslc · #6 02-17-2017, 04:25 AM

Embarrassed, embarrassed.
Just found out today that I have a K jetronic system not D-jet.
Spent a couple of hours with Naporn, he's the guy who fitted the engine a couple of years ago before the brown metal termites surfaced and started the whole rebuild. He was good enough to spend time showing me how to get things cleaned after a one year lay up. After a few minutes he said 'why are you calling it d jet when it's k jet.
Red face.
Anyway I'm hoping to post in a couple of days that she's running again

Idle · #7 02-18-2017, 10:27 PM

Fuel line pressure regulators are a thing you can buy. They come in different pressure ranges but most are adjustable within a set range, say, 4 to 9 psi, or maybe 1.5 to 5.5 psi.

Of course you would need a gauge on the discharge side of the regulator in order to set it correctly, but once set you could remove the gauge and install a plug in the gauge port.

These were all the rage during the late 70's when it was thought they would deliver better mpg. They didn't, but they did allow hot rodders to add a finer tune to their fuel delivery system.

I used one of these in the mid 70's on a large GM car from the late 60's and set it at 7 psi. The only improvement in mpg came from it acting like a fuel cut off when I stepped on the gas.

andyslc · #8 02-20-2017, 03:41 AM

Think now the intake plate and top unit where the six lines come out to go to the injectors have some internal problems so removing the unit and will get Naporn to strip and service the complete unit and then I'll refit it. The air plate only drops about a quarter inch then goes solid and that doesn't seem right.
Will update when it's off and I get a look inside.

andyslc · #9 02-21-2017, 04:22 AM

Don't understand why my air sensor plate is inside when the diagram shows it to be on the outside.
Can anyone tell which one is wrong, mine or the diagram.

andyslc · #10 02-21-2017, 04:31 AM

Downloaded diagram

Diseasel300 · #11 02-21-2017, 10:07 AM

The sensor plate is inside the main intake horn below the air cleaner. The diagram clearly shows that. For a better picture, see this one:

Frank Reiner · #12 02-21-2017, 10:39 AM

Quote:

Originally Posted by andyslc

Don't understand why my air sensor plate is inside when the diagram shows it to be on the outside.
Can anyone tell which one is wrong, mine or the diagram.

Neither one is wrong; they are two different types.

Quote:

Originally Posted by andyslc

Downloaded diagram

Quote:

Originally Posted by Diseasel300

The sensor plate is inside the main intake horn below the air cleaner. The diagram clearly shows that.

Actually the diagram posted by andy is for an up-flow type air meter (VW, Audi, Porsche, etc.), in which the sensor plate swings upward. MB uses a down-flow air meter, in which the sensor plate swings downward, as shown in the picture, not the diagram.

andyslc · #13 02-21-2017, 10:58 AM

Many thanks for the answers, it's one more thing of my mind.
Sometimes google might not be your friend.
Really am thankful for the help as here in Thailand it's sometimes difficult because of language problems and the vintage car scene is not a big thing. Most people here don't want anything other than a new car. You see many good old cars but the engines have been dumped and a Toyota lump stuck in. Just the other day I was looking at a lovely Jaguar 70's 4.2 saloon everything in lovely condtion but fitted with a Toyota lump, asking price 12,000 dollars.

andyslc · #14 02-21-2017, 11:22 AM

quick question.
How far should the air sensor plate go down?
On mine it can be gently pushed down about a quarter of an inch then it's a solid stop.

Frank Reiner · #15 02-21-2017, 01:54 PM

Quote:

Originally Posted by andyslc

quick question.
How far should the air sensor plate go down?
On mine it can be gently pushed down about a quarter of an inch then it's a solid stop.

andy,
If you remove the fuel distributor from the air-flow meter, you will then be able to swing the sensor plate thru its range (and a bit more).
Approx. 1.5 inches.