Mystery Part on manifold between the carbs

[kt]

69 1600

What is this line that runs into the center of the manifold coming
from both carbs? What does it serve?

There is also a cylinder type thingy attached to this center
area of the manifold, what is that??

I don't remember reading that in the copy of the service
manual that I have.

My roadster smells of fuel, and I am trying to track down
the location.

Thanks,

[DatsunBucky]

I checked my manual for a 67 1600, and I didn't see anything that fits that description. Is there an overflow on the carb bowl? The earlier models just dumped that out to the ground, but I don't know what the smog models do with overflow.

If the lines come from the smaller can on the carb, it could be the fuel bowl overflow is dumped into the intake manifold to be burned. If that's the case, I would suspect a stuck needle, or a needle that isn't shutting off the flow of fuel from the pump.

Kinda hard to tell without seeing it and doing some investigating, but if it is overflow, you should be able to see pretty easily by removing the top of the fuel bowl and seeing if the gas is way up, instead of in the middle somewhere.

Hope this helps.

Bucky

[S Allen]

Kt,

They are all part of the exhaust emissions control system on your car. The black thing mounted on the intake is a solenoid which is connected eletrically to several switches and through hose to each carb. It has something to do with vacum and burning cleaner. I am not sure of its exact operation but that is what it is.

Steve

[kt]

So, I spent today taking this thing apart to investigate.
The wires you talked about wasn't even hooked up! Which
means the intent of this part wasn't being performed!

Now, I have to track down where the 2 wires hook up to.
Looking at the wire diagram, looks like the part in question
is a By-Pass Valve.
It is hooked up in turn to a Clutch Switch, and a Transmission
Switch. Both of which I don't know where its located.
(Where are they located???)

Taking this part apart, I found that the black cylinder actually
controls a large(relatively) needle that pulls open and close
a valve to let additional fuel come into the manifold from the carbs.
The hoses that connect to the carbs, actually connects to a location
BEFORE the throttle butterfly, which means it controls the fuel
intake regardless of throttle. (Interesting, eh?)

Seeing as how my unit is not hooked up, and that the NORMAL position
of the valve is closed, Could this be the reason why I need 5 min warmup
periods?
I'm assuming the valve should be open on start, and after the engine
is warmed up, the valve closes.

I will attempt to hook up the wiring next weekend.
Any advice is much appreciated!

Thanks!,


(since this unit has not been functioning for so long,
the remaining fuel in the unit had turned yellow! )

[S Allen]

Nice investigative work. I would say the clutch switch may be located some where similiar to the brake light switch. On or near the pivot point of the clutch pedal arm. Look up under the dash near the clutch pedal. The tranny switch will possibly be on the same side as the reverse light switch on the passenger side of the tranny. And yes, this quite possibly is part of your warm up problems.

Steve

[kt]

Visual on Part in Question

[S Allen]

KT,

Straight from the manual "The later R engine has a solenoid valve which bypasses a "lean" fuel air mixture into the intake manifold for improved combustion. The solenoid valve is overridden if the clutch is not depressed or the transmission is not in third or fourth gear. This arrangement is operational primarily during deceleration, when high intake manifold vacum is present."

The clutch and transmission switches are located where I said they would be. It seems like this would cause problems more at higher speeds than at idle warming up. I no longer think this is related to your 5 minute warm-up problem. Sorry.

Steve

[TR]

Steve, you are dead on with the solenoid info. You can plug the lines and hole and remove it without any change in performance. If there is a change in performance it was faulty anyways.

Slow warm up is almost always due to the thermastat not functioning or being removed. If the car warms up but continues to run poorly, there is typically a mixture problem...

If you smell fuel, you should be able to find it. Check the hoses to the jets and the fit of the needle bodies. These sometimes leak when the choke is pulled (due to wear) and stop when the choke is closed but leave fuel everywhere. The other spot is the previously mentioned float needles. Also the overflow lines sometimes pull fuel if the vacuum is high in the air filter box due to a clogged or dirty filter. I highly recommend the ztherapy SU video to people new to the carbs and the experienced. I learned a lot from the video and I have had a few years experience with SU's...

Hope this helps! TR