Help with hooking up lines on 1977 Datsun 710 (California spec L20B I think)

[dcoolmech]

This is my first datsun ever, and my first carbureted car ever. I have finally finished rebuilding the DCH 340 Carb on the car just in the hopes of being able to pootle around in it... The long term goal is to do a complete drivetrain swap, the car in question is a California spec 3-speed auto, L20B 710 wagon.

 

I have no idea how to hook up lines on the carburetor. I have attached a couple based on best guesses, but I am not so sure about the rest. The reason for posting this is my fuel rail, engine bay and carb look slightly different than anyone else's I could find on the forum.

 

Pics to follow... I am open to any and all suggestions....

 

I am waiting on a replacement fuel nipple (thats why the exposed fuel inlet filter) to arrive in a couple of days. I assume that goes to the large hard line on the engine (fuel supply, assuming the device that traces back to on the other side of the engine is the fuel pump?)

 

There is a distributor line that I suppose is for advance. Which barb does that hook up to?

 

There is a line coming from a blue cylinder in the drivers side front corner with Japanese characters on it. I have no idea where that goes.

 

There are two additional lines parralel to the fuel rail - I think one of them comes from the thermostat housing - also no idea where that goes?

 

I am totally confused about the two barbs facing the drivers side above the float gallery.....

 

Please help... Pics to follow as soon as I can figure out how to upload them.

 

Thanks

 

Sanket

 

 

[]2eDeYe]

Welcome. :)

Pictures help ;)

 

http://community.ratsun.net/topic/691-how-to-post-pictures-and-keep-online-photo-albums/

[dcoolmech]

Welcome. :)

 

Pictures help ;)

 

http://community.ratsun.net/topic/691-how-to-post-pictures-and-keep-online-photo-albums/

Here we go...

 

 

 

 

 

That long rubbber line going to the front most barb on the left (engine side) comes from the distributor. This I did based on looking at someone else's pics from a different car.

 

HELP?!

[dcoolmech]

So I went ahead and hooked up some lines since I did not get a reply.

 

 

It seems the float chamber is nearly full with fuel, yet the engine does not seem to be getting any. The carb is completely dry...

 

Could someone advise?

[620Turbo4X4]

First thing I see is your choke butterfly is not closed in all of the photos. With a cold engine it should snap to within 1/4" of nearly shut when throttle is opened. Need to loosen the 3 screws on the black plastic housing and rotate it so butterfly nearly closes, and or, check for binding in the linkage.

 

Check that your accelerator pump is working? You should see a stream of fuel while looking down the primary venturi (closest to engine) while opening throttle.

 

Check to be sure that there is 12 volts going to both wires on carb. with key in ON position. One goes to choke, other to a idle fuel shutoff solenoid.

 

Can't really help with all the lines, but the two ports on the engine side of carb go to the metal line / fuel rail. Front port to top line that (T's) at the distributer, going to purge canister (the blue cylinder) and vacuum advance on the dist. Rear port is for the EGR and plugs into the lower metal line, then to thermostat, and EGR valve. Wouldn't really worry about that atm unless you need it to pass emissions.

 

For the ports on the driver side, it looks like the two lines running adjacent to the one that is hooked up go to carb. Can't tell from photo where they are going now..

 

As long as there are no vacuum leaks it should run after all the above is checked and functional...

[dcoolmech]

First thing I see is your choke butterfly is not closed in all of the photos. With a cold engine it should snap to within 1/4" of nearly shut when throttle is opened. Need to loosen the 3 screws on the black plastic housing and rotate it so butterfly nearly closes, and or, check for binding in the linkage.

 

This is easy... I will fix this first. I am sure there is no binding, just a question of rotating the housing like you said.

 

Check that your accelerator pump is working? You should see a stream of fuel while looking down the primary venturi (closest to engine) while opening throttle.

 

I will probably need a second set of eyes when I do this.. I will check.

 

Check to be sure that there is 12 volts going to both wires on carb. with key in ON position. One goes to choke, other to a idle fuel shutoff solenoid.

 

Check - they are good.

 

Can't really help with all the lines, but the two ports on the engine side of carb go to the metal line / fuel rail. Front port to top line that (T's) at the distributer, going to purge canister (the blue cylinder) and vacuum advance on the dist. Rear port is for the EGR and plugs into the lower metal line, then to thermostat, and EGR valve. Wouldn't really worry about that atm unless you need it to pass emissions.

 

For the ports on the driver side, it looks like the two lines running adjacent to the one that is hooked up go to carb. Can't tell from photo where they are going now..

 

I'll upload a pic or two if I still have trouble.

 

As long as there are no vacuum leaks it should run after all the above is checked and functional...

 

Thank You.  I will report back on how it goes...

[dcoolmech]

Great News!!! It started..... Many times... :thumbup: :thumbup: :thumbup: I was able to get it warmed up even.... However it still won't idle without my foot lightly on the throttle. Seems to be getting too much air/ Leak?

 

 

I've marked up the connections I have made, and am in doubt about the two barbs on the driver side that I have circled. Is it safe to just cap these off with vacuum caps?

 

Throttle response in Neutral seems to be great... I just need to be able to get it to idle properly so I can DARE put it in Drive.

 

I tried turning the idle adjustment screw both ways (1.5 turns at a time), but that did not seem to make any significant difference. What does this screw adjust, bypass air or fuel?

 

I'm so excited that I am very close to driving this thing after having it sit for nearly 1.5 years.... :w00t:

[datsun 160J SSS]

don't do engine mods if you have to do CA star smog check it's a big pain in the ass .or find a early year model and swap the vin... just my 2 cents

[dcoolmech]

I feel sorry for California people. I am in Michigan... No smog checks.. :D

 

 

don't do engine mods if you have to do CA star smog check it's a big pain in the ass .or find a early year model and swap the vin... just my 2 cents

[]2eDeYe]

You should be able to cap those. Likely they are creating a vacuum leak causing the lack of idle. With it running you can check for leaks by choking the carb down with your palm over the throat (replicating that 1/4" gap mentioned earlier) if it idles up you have leaks. You can spray carb clean around the base of the carb and where the intake meets the head, also with it running, to pinpoint the leaks. It's likely plugging those lines would do it, not sure where they really go as I haven't played with a hitachi in a long time.

[dcoolmech]

So I plugged every unused line I could find... No difference...

 

I played with the idle adjust screw - but it clearly does not have enough authority to tackle whatever the issue is.

 

I did the hand over the carb test - the engine clearly revved up some...

 

I sprayed carb cleaner at the base (where the carb meets the intake) and I thought there was perhaps a slight increase in RPM. The question I now have is: how do I tighten the front most nut on the engine side with all those hard lines in the way? I cannot seem to get a good grip on it from any angle. I further tightened the remaining 3.

 

Is there some trick I am missing?

[datzenmike]

 

 

No need to capitalize, my ears hurt.
 

The idle mixture screw is the one on the base of the carb with the spring on it. Turning out increases the fuel mixture. The idle speed screw, also with a spring, is over to the left and partly hidden by a vertical linkage. Turning out reduces the idle speed .
 
The hex shaped unit with the red wire is the idle cut solenoid. With the ignition on you should hear a click sound if it is working. When on, the idle cut solenoid allows fuel down to the idle mixture mixture screw. If there is no power to the idle cut solenoid there can be no fuel for idling and it won't run.
 
With the motor warmed up and running and idle turned as low as you can, turn the idle mixture screw in until the idle quality drops. It may already be bad and if so turn out. Find a place where the idle increases and improves. Keep turning out until the idle quality drops. Back up to find a place about half way between. Usual;ly there is about a turn and a half where it runs well just pick a position in the middle. Likely the idle speed has picked up, so reduce the  RPMs by turning the idle speed screw out. Go back to the idle mixture screw and turn in till it stumbles, then out till it stumbles and set about half way between where it idles the smoothest and reduce the idle with the idle speed screw. Continue adjusting as many times as needed until you cannot improve the idle quality and idling smoothly around 750-850. This adjustment only affects idle and has NO effect on anything above that.
 
 
 
 

 
The large round black object is the electric choke heater. When cold the coiled spring inside holds the choke plate closed to provide a rich mixture to aid in starting. The electric heater warms the choke spring and it expands and uncoils slowly, opening the choke plate as the motor warms up. If you look carefully the choke heater wire is usually blue. Power is only on when the motor is running and not to be confused with the idle cut which is on when the key is on.
 
 

 
With the motor cold, depress the gas peddle once. The choke plate should snap closed over the primary barrel as in the picture above. When the motor is started the choke linkage also engages a fast idle cam to rev the motor to speed the warm up. As the motor warms up (about 8 minutes)  the choke plate will rotate open fully. If only part open check for power on the blue wire to the choke heater. Depressing the gas will disengage the fast idle.

[dcoolmech]

My idle speed screw is missing. Likely this is the culprit. I have another carb I was using for parts that I will take one from, and report back on how it goes. Wish me luck everyone, I have to itching to drive this thing for almost 2 years.

 

 

 

No need to capitalize, my ears hurt.
 

The idle mixture screw is the one on the base of the carb with the spring on it. Turning out increases the fuel mixture. The idle speed screw, also with a spring, is over to the left and partly hidden by a vertical linkage. Turning out reduces the idle speed .
 
The hex shaped unit with the red wire is the idle cut solenoid. With the ignition on you should hear a click sound if it is working. When on, the idle cut solenoid allows fuel down to the idle mixture mixture screw. If there is no power to the idle cut solenoid there can be no fuel for idling and it won't run.
 
With the motor warmed up and running and idle turned as low as you can, turn the idle mixture screw in until the idle quality drops. It may already be bad and if so turn out. Find a place where the idle increases and improves. Keep turning out until the idle quality drops. Back up to find a place about half way between. Usual;ly there is about a turn and a half where it runs well just pick a position in the middle. Likely the idle speed has picked up, so reduce the  RPMs by turning the idle speed screw out. Go back to the idle mixture screw and turn in till it stumbles, then out till it stumbles and set about half way between where it idles the smoothest and reduce the idle with the idle speed screw. Continue adjusting as many times as needed until you cannot improve the idle quality and idling smoothly around 750-850. This adjustment only affects idle and has NO effect on anything above that.
 
 
 
 

 
The large round black object is the electric choke heater. When cold the coiled spring inside holds the choke plate closed to provide a rich mixture to aid in starting. The electric heater warms the choke spring and it expands and uncoils slowly, opening the choke plate as the motor warms up. If you look carefully the choke heater wire is usually blue. Power is only on when the motor is running and not to be confused with the idle cut which is on when the key is on.
 
 

 
With the motor cold, depress the gas peddle once. The choke plate should snap closed over the primary barrel as in the picture above. When the motor is started the choke linkage also engages a fast idle cam to rev the motor to speed the warm up. As the motor warms up (about 8 minutes)  the choke plate will rotate open fully. If only part open check for power on the blue wire to the choke heater. Depressing the gas will disengage the fast idle.

[dcoolmech]

It runs... I was missing the idle speed adjust screw.... Everything runs great.. .I even drove it around my neighbourhood.... I am super stoked.

 

Thank you for the help. :thumbup:

 

Sanket