only running on one carb HELP PLEASE

[JeffMopar]

Hello,

Finally got some time to try to get the Z running. I have the original 3 screws that came on it rebuilt with Ztherepy kits. Got It to start fine and run without the choke after a little warming up. Idles at about 750 to 800. Started to adjust and balance the carbs and realized the rear carb isn't working. I can screw the mixture dial all the way out or in tight and there is no change at all. If I cover the carb with my hand or lift the piston nothing changes. The front carb adjustment works the way it should. I have set the float with the 10 turns down method and verified that the fuel is flowing to that level and stopping at the right height. But cant figure out what could be keeping the fuel from getting into the carb body the way it should!! Any help is appreciated.

Thank You, Jeff

[Patcon]

There is fuel in the rear float bowl? Verify visually. If there is fuel in the float bowl then there is a blockage somewhere. Bowl outlet, connector hose or the base of the jet tube...

[JeffMopar]

Yes there if fuel in the float bowl. I drained it and did a verification on the fuel height again to make sure it was correct. I am probably going to have to break down and take the carb off and disassemble it again to make sure everything is correct and clean. The car hasn't run since 1990 and I did a complete restoration. This is just working out the little bugs as you go and it gets aggravating. Thanks

[siteunseen]

You could stick the little red straw off a WD-40 can down the overflow bung and see if you can slightly push down on the float.  The float could be stuck?

The barrel screen on the banjo bolt, where the fuel line is connected on top, could be clogged too.

Here's a pretty good read talking about cars sitting for awhile.

 

[JeffMopar]

I didn't think of the red straw idea. I will try that to see if the float is up. I completely rebuilt the carbs and removed the screens from the banjo bolt when disassembled. The only thing I can think of is that the float is sticking randomly, not all the time.

[Patcon]

Did you replace the screens in the banjo bolts after rebuilding? They are important...

[siteunseen]

21 minutes ago, Patcon said:

Did you replace the screens in the banjo bolts after rebuilding? They are important...

The ZTherapy DVD says pull them off, potential restriction.

I have one of these before the fuel rail. 

 

[JeffMopar]

They are not needed if you have a good filter. The fuel in the bowls is totally clean. I installed a filter below the floor pans out of the way and still use the original style so it looks stock. I am going to remove the vent bung tomorrow and check if there is enough room to see inside to verify fuel is entering to keep the bowl full after starting. It fires up very fast with the choke on so I am thinking maybe it is sucking fuel below the level it needs to maintain but the needle is sticking partly and not refilling fast enough.

[madkaw]

Cliff,
Your not really running that filter are you?


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[Mark Maras]

  I'm assuming that when you block the carb with your hand, you're feeling a lot of suction. Fuel level appears to be normal in the bowl. Is it possible that the nozzle is staying down in the full choke position even though the choke knob is pushed into the off position? Occasionally, the flat linkage piece that connects the cable to the nozzle needs a bit of a twist to function properly. Try pushing the nozzles up from the bottom with the choke knob off and see if either one will "click" into place. A bit of lithium grease on the sides of the nozzles is a good idea too. Kinda grasping at straws but I've not experienced a carb that does nothing when the piston is lifted.

[Captain Obvious]

Well I'll be the dissenting voice and offer a completely different theory. I propose that you may be running on one carb only because the butterfly for the other carb is closed. In other words... It's getting fuel to the bowl, but the butterfly is slammed completely shut.

If that's the case, you can lift the piston and nothing will happen. You could also adjust the nozzle mixtures and nothing will happen. You could hold your hand across the carb face and nothing would happen. A full bowl, and none of it will ever leave the bowl because there's no airflow to pull it out of the nozzle.

Pulling the choke lever also opens the throttle plate a little and that would explain why yanking the choke makes it run OK while the choke is pulled.

Did you do any rough sync of the carbs after you installed the carbs and linkage? What happens if you manually push the linkage for the rear carb open a little with your hand?

[Chickenman]

Edit: Dang Capitano Obvious beat me to it while I was downloading fancy pictures. I concur with CO.

What happens when you Rev the engine rapidly? Does the rear piston lift and the engine respond halfway decent? You may just have the front and rear carbs really out of balance. Throttle blade wise.  Rear throttle blade closed at idle...= no airflow = no fuel draw = no idle difference when piston lifted manually. 

happens all the time on Triples and happens on SU's as well. Do you have a Carb balancing tool?

 

 

 

 

Edited March 31, 2017 by Chickenman