2800cs zenith wiring

[Baikal Bimmer]

Hi everyone,
as many of you know, I have recently purchased a second e9 (1972 2800cs).
The car idles at 2100 rpm, and after reading through many older threads and posts here on the forum I have come to the conclusion that the chokes on the carburetors are not receiving power.
The carbs each have their own tiny wiring harness but no wiring that connects them or provides either the front or rear carb with power.
In the pictures I have attached, you can see a green wire with a white stripe that has been cut, and a black and red wire with spade connector. Are these wires involved with the carburetors? Do the cut green wires need to be reconnected?
Any advice is appreciated

 

[eriknetherlands]

I think so, these green white connectors connect to the carbs, at least they did on mine carbed 3.0 cs.
I'll add some pics tomorrow.

The alu cans on the firewall side should get power in some way.

Also the rectangular blocks, on the left side (looking from the driver) need to get power in some way.

In my car, the carb harness was one unit, connecting ( from memory) at least both carbs, a sensor at the front of the engine, and a relay on top of the brake booster.

Edit- also the shut off valves at the bottom of the carbs need to get power in some way

 

[stphers]

This is where you need to have a look at a wiring diagram to see where all the connections are.

Thanks, Rick

 

[HB Chris]

Well for starters, your chokes aren’t synchronized, one is open and one is closed. You need to loosen the three screws holding the front water choke, loosen the 13mm bolt in the center but don’t remove, and then rotate the cylinder housing so the spades are on the top, yours are facing the fender on the front carb. This is how you adjust the opening of the chokes which must be slightly cracked open when cold. You might need to shoot penetrant on the tiny vertical rod/plunger and the butterfly pivots, they need to move freely. I have the wiring for these and it is indeed one harness, I will post later my drawing with wire colors. They connect to the relay mounted to the booster.

 

[eriknetherlands]

Some pictures for my carb harness, while removing it from the car:

the harness connects to the relay on top of the brake booster; it's this one marked "B" in my pictures:

it has the connectors attached from the carb harness:

The carb harness uses some special connectors that are nowhere else used on the car (on my car that is, which looked to be quite original). Note the shape of the connector with the '6' and '7' and "HSU" in the diamond on the connectors? These ones are specific to the carb harness.

 

[eriknetherlands]

Some other talk on carb harness here:

https://e9coupe.com/forum/threads/zenith-carb-connections.19176/

 

[eriknetherlands]

Let me know if this is enough, i can also run in the garage, and pull out the carb harness from a storage box , lay it flat, and send you a picture.

 

[deQuincey]

Hi everyone,
as many of you know, I have recently purchased a second e9 (1972 2800cs).
The car idles at 2100 rpm, and after reading through many older threads and posts here on the forum I have come to the conclusion that the chokes on the carburetors are not receiving power.
The carbs each have their own tiny wiring harness but no wiring that connects them or provides either the front or rear carb with power.
In the pictures I have attached, you can see a green wire with a white stripe that has been cut, and a black and red wire with spade connector. Are these wires involved with the carburetors? Do the cut green wires need to be reconnected?
Any advice is appreciated

so the car iddles at 2100rpms, but when ? when it is cold, or when it is warm ? to me this is the starting question

you have the chokes and the air valves and the coolant passing effect, too many things and too messy looking carbs

many things may happen there, not only the chokes, how is the triangular membrane screw stop set ? is the 2,8mm gap for the primary butterfly correctly set ?

again, IMHO those electric connections are not so relevant, you might have to look deeper, maybe clean and rebuild them to know the floor in which you are standing.

 

[Baikal Bimmer]

Some pictures for my carb harness, while removing it from the car:

View attachment 141652

View attachment 141651
View attachment 141650
View attachment 141649
View attachment 141648

the harness connects to the relay on top of the brake booster; it's this one marked "B" in my pictures:

View attachment 141653
it has the connectors attached from the carb harness:

The carb harness uses some special connectors that are nowhere else used on the car (on my car that is, which looked to be quite original). Note the shape of the connector with the '6' and '7' and "HSU" in the diamond on the connectors? These ones are specific to the carb harness.


View attachment 141654

My car doesn’t have that relay on the brake booster, maybe a difference between 3.0 and 2.8 cars?

 

[Baikal Bimmer]

so the car iddles at 2100rpms, but when ? when it is cold, or when it is warm ? to me this is the starting question

you have the chokes and the air valves and the coolant passing effect, too many things and too messy looking carbs

many things may happen there, not only the chokes, how is the triangular membrane screw stop set ? is the 2,8mm gap for the primary butterfly correctly set ?

again, IMHO those electric connections are not so relevant, you might have to look deeper, maybe clean and rebuild them to know the floor in which you are standing.

The car idles idles at 24-2500 when cold and 2100 when warm.

 

[HB Chris]

Wiring diagram attached. As the wires share a black plastic sheath it is hard to tell where a couple go near the relay. The green/white wires go to the idle solenoids and are always powered or your car won’t run. Unfortunately the factory wiring diagram doesn’t show the wires for the idle solenoid and aux device. Green power comes from fuse #7. The temp sensor cuts off ground I believe for the chokes themselves.

 

[Baikal Bimmer]

Alright, I have adjusted the water chokes and connected my carb harness to the carbs. On both the front and rear carbs the second spade is not connected to anything, based on the above diagram this is where the two carbs join together.
I don’t seem to have the choke relay??

what happens with these cut wires?

 

[deQuincey]

The car idles idles at 24-2500 when cold and 2100 when warm.

so you might need a full revision

it should be 1400 cold and 950 warm

your chokes are doing very little, but they are doing so me thing

andthere must be some current in the iddle solenoids as the engine runs

 

[Baikal Bimmer]

so you might need a full revision

it should be 1400 cold and 950 warm

your chokes are doing very little, but they are doing so me thing

andthere must be some current in the iddle solenoids as the engine runs

There is definitely no current, I checked with my electrical tester. I can also see that wires are missing/cut.
Maybe my water chokes are working but not the electric

 

[deQuincey]

There is definitely no current, I checked with my electrical tester. I can also see that wires are missing/cut.
Maybe my water chokes are working but not the electric

read carefully, there must be current in the iddle solenoids

and yes the chokes work on electric and on water

 

[Baikal Bimmer]

read carefully, there must be current in the iddle solenoids

and yes the chokes work on electric and on water

Sorry, I understand what you meant,
That I need to have current to the solenoid

 

[HB Chris]

Alright, I have adjusted the water chokes and connected my carb harness to the carbs. On both the front and rear carbs the second spade is not connected to anything, based on the above diagram this is where the two carbs join together.
I don’t seem to have the choke relay??

what happens with these cut wires?

You need the missing relay

 

[HB Chris]

Alright, I have adjusted the water chokes and connected my carb harness to the carbs. On both the front and rear carbs the second spade is not connected to anything, based on the above diagram this is where the two carbs join together.
I don’t seem to have the choke relay??

what happens with these cut wires?

Second spade is not used, if wires to the chokes are not hooked up it will still run fine just harder starting when cold.

 

[Baikal Bimmer]

S

Second spade is not used, if wires to the chokes are not hooked up it will still run fine just harder starting when cold.

interesting, I didn’t know that. What about the two cut green and white wires in one of my previous pictures, reconnect??

 

[deQuincey]

Sorry, I understand what you meant,
That I need to have current to the solenoid

please try to differentiate, the iddle solenoid is key for running engine, if it has no power the iddle solenoid blocks the iddle circuit and engine does not run


the choke resistance (yes the spades feed 12v on an internal resistance) collaborates with the coolant heat, if this resistance is not electrically fed, simply the automatic choke will take more time, engine will not run harder, it will take more time for the primary butterfly to open fully and to reduce rpms to warm iddle