TheSamba.com :: View topic - Fuel cut-off wiring for dual carbs?

Wed Mar 12, 2008 10:57 am

I may be retarded but I did not see details on this in the FAQ. Is there anything that shows how the fuel cut-off deals (or whatever they are called) should be wired?

I know... BENTLEY!! I cannot find one. None on ebay, none on Amazon. They have them for other years, just none for 67.

Wed Mar 12, 2008 12:11 pm

I bought a Volkswagen 1600 Fastback 1965-70 Autobook Manual by Kenneth Ball at books4cars.com.

Wed Mar 12, 2008 12:25 pm

http://www.thesamba.com/vw/archives/info/wiring/type3_1600_67.jpg

Wed Mar 12, 2008 2:02 pm

Or do you mean an "impact switch" to kill the electric fuel pump in an accicent?
Do a search on "impact switch".

Wed Mar 12, 2008 4:54 pm

Air-Cooled Head wrote: Or do you mean an "impact switch" to kill the electric fuel pump in an accicent?
Do a search on "impact switch".

I am going to go ahead and sound like an ass here so we can get to the point… To be honest with you I do not know. I haven’t had a T3 in over 10 years. I bought one last week and while awaiting delivery I have been reading the board daily. I was reading on another thread where a guy couldn't keep an idle on a dual carbed motor. Car ran fine except for that. He mentioned something wasn't hooked up and I saw something about a cut off switch. I think it was supposed to be hooked up to the coil.

I received my car late last night. What looks like the choke is not hooked up. I didn't look to see if there was a cut off switch on the carb... I wasn't even aware there was such a thing. I didn’t know that 67’s had impact switches or anything like that. So, I guess I should begin at the beginning – do 67’s have some sort of cut-off switch on the carb? Is this synonymous with the impact switch?

Wed Mar 12, 2008 5:02 pm

Choke. Hook to ignition side of the coil.

Wed Mar 12, 2008 5:11 pm

I think he means the idle cut off valve on the side of the car that wires through the choke. I think it was in abgwins thread.

Wed Mar 12, 2008 5:40 pm

austin_v694@yahoo.com wrote: I think he means the idle cut off valve on the side of the car that wires through the choke. I think it was in abgwins thread.

That sounds familiar.

Wed Mar 12, 2008 5:50 pm

Sticks out the side of the carb outboard. Few inches long, maybe an inch diameter. You can wire that to the ignition side of the coil to or to the choke if it is hooked up to electric. It is not an impact cut-off switch. It is an ignition cut-off switch.

http://www.thesamba.com/vw/classifieds/detail.php?id=517406

Wed Mar 12, 2008 6:04 pm

What is the idea behind them - what were the engineers trying to accomplish?

Wed Mar 12, 2008 6:07 pm

2dollah wrote: What is the idea behind them - what were the engineers trying to accomplish?
Eliminating run on. Works very well.

Thu Mar 13, 2008 7:16 am

yep, I had posted quite a bit about getting mine right. I used the wiring diagram here on the samba (look under technical) for a 67 since it's 12v and still had dual carbs.

I think what's correct is for the wires from the cutoff to connect to the choke and then to the coil.

Fri Mar 14, 2008 10:15 am

If worried about fuel system during accident or with just the key in the ingnition, I would suggest a oil pressure cut off switch. I purchase them from Summit racing. They will cut off power to fuel pump if oil pressure falls below pre-set limit. Wiring is easy and wont drain battery if you just want to listen to tunes without engine running,

Fri Mar 14, 2008 12:58 pm

My fuel pump is mechanical so that's why I don't understand the purpose of these things. Why the hell are they there? What was VW trying to accomplish with them? Can I just plug the hole with a bolt and it will run OK.

Fri Mar 14, 2008 1:02 pm

Early Rabbit FI relay. It has an additional terminal that connects to the negative side of the coil. When the engine cranks or is runig, it powers the electric pump. If the engine stalls, it turns the pump off.

Fri Mar 14, 2008 1:05 pm

To cut off fuel supply AT THE CARB when you turn the key off.

Fri Mar 14, 2008 1:39 pm

Air-Cooled Head wrote: To cut off fuel supply AT THE CARB when you turn the key off.

Thank you.

Fri Mar 14, 2008 2:31 pm

Does the relay above allow the pump to continue running in the ignition position, so in an accident, the engine could stall but the pump would continue to run until the key is turned off?

The only set up I have seen that kills the pump is a double relay, one for start then one for run, auto switching and the oil pressure cut-off.

Fri Mar 14, 2008 5:26 pm

Air-Cooled Head wrote: To cut off fuel supply AT THE CARB when you turn the key off.

2dollah wrote: Thank you.
It cuts off the fuel at the pilot jet. It does not cut-off fuel supply to the carb. The pilot jet works with the air correction jet and supplies fuel thru drillings to the volume control screw for idling. The electric cut-off shuts the pilot jet. This is an idle circuit. It doesn't shut off fuel to the running circuit.
2dollah wrote: My fuel pump is mechanical so that's why I don't understand the purpose of these things. Why the hell are they there? What was VW trying to accomplish with them? Can I just plug the hole with a bolt and it will run OK.
No. You do not need an electric pilot jet but you do need a pilot jet.
The pilot jet sans electric cut-off is near the center of this carb shot. It is right above the accel pump in line with the volume control screw.
Right side carb.

Fri Mar 14, 2008 6:03 pm

busman78 wrote: Does the relay above allow the pump to continue running in the ignition position, so in an accident, the engine could stall but the pump would continue to run until the key is turned off?

The only set up I have seen that kills the pump is a double relay, one for start then one for run, auto switching and the oil pressure cut-off.

No, the FI control unit suts off the pump, if the engine stops running. This is what is going on when you hear the 2 relay clicks when you turn the key on.
The ECU powers up, and turns on the pump, but then 1-2 seconds later if the engine isn't cranking with the starter, or the engine isn't running, it shuts the pump back off.

The double relay is for a AFC FI only. Like would be in a Type 2.