How to tune carbs JUST to get the car running?

[kayinsunz]

New to the forum and already feel welcome, thank you for that.

Anyways, thanks to a suggestion Zed Head, I was able to hear my 240z sputter up for time last night. Unfortunatly, it won't stay running for more than 30 seconds. The guy I bought it from said it was running good when he parked it, but then he tried to adjust the carbs and screwed them up. It sputters up after cranking for 10 seconds, and within 15 seconds fuel is pissing from the float intake hose, and soon after starts pissing out of the carburator air horn as the engine misses, backfires, and dies.

What am I missing?

I can already tell this forum is a plethora of information so if there is a similar thread I miss feel free to send me that way. Thank you for any suggestions.

-KS

[240260280]

Sounds like the fuel pump pressure is too high or the needle valves in the fuel bowls are no closing.  Check to see what kind of pump is installed on the car.

 

Carbs only need 3  to 4 psi.

 

If you have just the stock pump then take the fuel bowls apart and get the needle valves to work.

 

 

 

Edited June 13, 2017 by 240260280

[240260280]

 

[kayinsunz]

It's an electrical pump rated 5.5psi to 9psi. Could this explain why it hardly runs? Is it flooding?

[Patcon]

That's too much pressure...

[kayinsunz]

Ok cool so I will need to buy a pump with a lower PSI rating. Would that explain why is pissing fuel and sputtering like so?

[heyitsrama]

My Z had this issue, what I did was open the float bowl, remove the needle, take it apart and clean, and put back together.

You might need a gasket if the old one is old. Try blowing air through the gas inlet, while lifting the float up to see if it's able to seal correctly.

After you have this all done, turn the page to the service manual and get a base tune.

Might be worthwhile to grab a carb tune. I thought mine was good, but my front was around 13 mmHg while the rear was probably around 7, I had the impression it was running good until I got my hands on the tool, and got them both on an idle around 12, now it's running like butter.

Good luck, ask good questions, read and reread.

[240260280]

You can put a fuel regulator down stream to get you out of the water but if it ever fails you could have fire risk.

[kayinsunz]

Ok so first, I will try to open up the float bowls, check the float bowls, and clean up the needle valve with carb cleaner. Gonna grab my fuel pressure guage from work and test the fuel PSI after the regulator. 

Edited June 13, 2017 by kayinsunz
off topic

[kayinsunz]

So I tied off the hose I have in an attempt to reduce pressure and it purred like a kitten for about 2 mins untill it flooded the float bowls again. Going to replace the pump with a lower pressure pump, and will post the results. Thank you gentlemen.

Edited June 13, 2017 by kayinsunz

[240260280]

We got your back on this forum.  Come back anytime you have a question.

[heyitsrama]

When you replaced the pump was it with a high pressure unit? Or an OEM equivalent? How did you clean the floats? I had to actually disassemble the valve inside the float and clean the seat.