TheSamba.com :: View topic - 34PICT-3 Carb Won't Idle

Mon Nov 03, 2025 6:55 pm

I've tried searching but there are so many with issues similar to mine, but not quite. I just can't decipher what I need to do next to troubleshoot.

I installed a new 34PICT-3 carb from JBUGS, P/N 113129031KJB. Installed last Nov. Got it running and idling pretty well, just had an icing problem. I decided to leave it as is and come back to that when I got all the body work and painting done and was ready to start driving it. That time has come, and now the car will not idle.

The only thing I've touched on the carb since last year is installing a new accelerator cable. There was about 2 gallons of gas that sat in the tank since last year. I cleaned out all the old gas and add fresh and made sure it was pumping clear through the fuel pump.

Troubleshooting so far:

I changed out the fuel filter. Checked to make sure fuel is flowing to the carb. The cut-off solenoid is good. I removed the top of the carb and checked that the bowl was full of fuel and the float is not sticking. I removed the cut-off solenoid and sprayed carb cleaner in the hole, re-installed the solenoid.

The car will start and I can keep it running if I give it gas. As soon as I let it idle I get about 10 seconds and it will die. I've tried adjusting the screws on the side but I can't get it to idle.

Any help will be appreciated.

Mon Nov 03, 2025 9:04 pm

Idle jet is probably clogged up because the gas sat for so long. The ethanol gels.

Time for a carb clean.

Mon Nov 03, 2025 10:35 pm

talljordan wrote: Idle jet is probably clogged up because the gas sat for so long. The ethanol gels.

Time for a carb clean.

Remove idle jet and spray cleaner in the passage.

Try unscrewing the idle jet a little (up to 1/4 turn or so) while revving, can help clear the passage of blockage that the jet size will not.

Tue Nov 04, 2025 4:34 am

Before taking it apart, I would spray carb cleaner into the idle jet circuit as stated before in this thread, but leave it for an hour or 2, and then blow out the circuit with compressed air to try and dislodge any possible blockage. If that does not work a carb disassembly is in your future.

Tue Nov 04, 2025 7:50 am

Thanks for the replies. I'll work on spraying out the idle jet today and see what happens. I didn't want to tear down the carb if at all possible. I actually had to buy this one because I attempted to clean the old one and lost a tiny ball bearing.

I'll post tonight with the results.

Tue Nov 04, 2025 1:14 pm

Ok, so I took out the idle jet screw and sprayed carb cleaner in the hole. I also used a small needle and cleaned out the holes on the jet and sprayed it with carb cleaner as well. I let it sit for a couple hours and then started it.

It fired up and now idles...thank you!

It sounded like it's idling a little high so I tried to make some adjustments but running into another problem. I'll explain what I did and see if anyone can help further.

After warming the engine up I adjusted the fast idle screw in all the way until it touched the bottom of the step cam, and then turned in another 1/4 of a turn.

I turned both the large screw and smaller screw beneath in all the way and then out 2.5 turns. I think these are idle control (large) and air mixture (small)?

Started the car up and turned the idle screw out until I had the highest RPM which was about 1750. I then turned the small (air) screw in until the RPMs dropped about 50-100 RPMs. I then tried to adjust the idle screw in again to get 900RPM. This is where the trouble started. I can't get it to stay at 900. I can get to about 1200 and it will be "somewhat" steady. Once I get much below that it will jump from about 1150 down to 750 area and eventually die.

I read that it could be an air leak. To check I sprayed carb cleaner all around the manifold, all the adjustment screws and idle jet, and the seam where the carb connects to the manifold. The only increase in RPM was around the idle jet screw and where the carb connects to the manifold, but it was very little...less than 30RPM change.

What am I doing wrong here?

Tue Nov 04, 2025 1:24 pm

I think you did this backwards after the starting point of 2.5 turns out. Turn the LARGE idle screw in to get to say 900 RPM at idle. Then turn the SMALL volume screw out to get to the highest idle w/no stumble, then in until it just drops. Then back out 1/8-1/4 turn. Then use the LARGE idle screw to get the idle back to 900. That's how I start.

Then I take the car on a good drive to get the engine up to completely normal operating temps, since idling in the driveway doesn't really do that. Once at full operating temps, then I pull over and readjust the idle, figuring it will be best w/the engine at these temps.

That's my 2 cents.

Tue Nov 04, 2025 3:03 pm

I was starting to redo the adjustments the way vamram explained and I decided to spray some carb cleaner one more time just to be sure there were no air leaks. It did increase RPM slightly when I sprayed on the idle jet, and I removed that to clean it out so I tightened it a little more. I then tightened the 5 screws on the top of the carb just a little bit because I did have that off the other day when checking the float.

As I was spraying the carb cleaner one more time to verify it fixed the slight RPM increase, a nasty noise instantly started. It sounded to me like the belt pulley rubbing so I stopped the engine and turned it manually and it's not touching anywhere.

I took a video and uploaded it to YouTube if anyone would mind taking a listen and see if maybe they notice something.

https://youtube.com/shorts/JfXz--VZBZ4?feature=share

Since this post started as a carb issue I'll go ahead and start another post for the engine noise too.

Thank you.

Tue Nov 04, 2025 4:00 pm

Sounds like the degree pulley is hitting the pulley tin IN FRONT of it - between the pulley and the engine block/oil pump. You'll see some silver dust around there if that's the case.

Tue Nov 04, 2025 4:16 pm

vamram wrote: Sounds like the degree pulley is hitting the pulley tin IN FRONT of it - between the pulley and the engine block/oil pump. You'll see some silver dust around there if that's the case.

I didn't think that was the case because I rotated it manually and didn't hear anything, but I pushed down on the tin there and it stopped. When I let off it starts again, so you are right. I need to make some tin adjustments.

Still can't get it to idle at 900RPM though. Is that strictly a carb issue or could something else engine wise cause that?

Tue Nov 04, 2025 4:19 pm

Make sure everything is tightened down w/out stripping anything - carb top, base at the manifold, etc. Set the carb to the base 2.5 open for the volume and idle screws, let it warm up, time it once you've got the idle to 850-900, then check the timing again, drive it to get it hot, reset the carb.