SU's got me stumped

[cozye]

Steve,

Take the hood off and have someone else drive the car while you ride on the fender hunkered over the motor. I'm sure it wont help solve the issue, I'm just curious what the ticket will read like..... "Well, your honor, this dimwit out in Oregon said that if I were to ......... " :stupid:

maybe like this

http://www.youtube.com/watch?v=OIjvqx7sxb0

[Bruce Palmer]

And the wind across her belly button whistles a perfect middle C. That's pretty funny stuff. Stupid but funny.

[steve91tt]

Just a quick update...

The front carb is still giving me grief but the good news is that I have figured out how to reproduce the problem.

I had been babying the motor as I was still breaking it in. But now that it has +1000 miles on it I am leaning on the gas peddle a little more now. As it turns out the front slide sticks 25% of the time when I do a 2nd gear red line run. I am able to confirm that it sticks because I now have the idle set high enough (1100 RPM) that when the front slide sticks the car keeps running (500 RPM, but very rough).

When it sticks I can remove the air cleaner and physically feel that the slide on the front carb is much higher than the rear. If I shut the car off, remove the damper plunger and actuate the slide up and down a couple of times all is well again until my next full throttle run.

I have done this 4 times today with dome adjustments and cleaning in between. The front slide is definitely sticking.

I'm working with the good folks at ZTherapy right now. I'm sure we will get is solved soon. I'll keep this thread updated.

[Gary in NJ]

OK, so now you know you have;

- a dirty (soot) suction piston

- a flaccid spring

- a misaligned needle, or

- a clogged nozzle, or

- a jet with a burr, or

- a combination thereof.

[steve91tt]

- a dirty (soot) suction piston

I'm on my second piston dome set and both sets were carefully cleaned and deburred.

- a flaccid spring

Never thought of that but the front and rear carb both decend at the same rate both with and without the damper valve installed. I'll try swapping springs tonight.

- a misaligned needle

I have aligned it many times trying to get the issue to go away. The piston moves up and down with no resistance when the engine is turned off.

- a clogged nozzle

potentially so. I have not checked.

- a jet with a burr

The needle is smooth to my fingers and is straight as far as I can tell.

- a combination thereof.

[patjamejam]

I SOO Feel your pain. Gotta feeling it isn't solely carb related . I would now look at a short in the dist ....frayed wire / Bad connection...or from coil to dist.

Recently I had the same problem....went on for months....in summer was convinced it was vapor look.....if i waited a while she'd start right up..... sometimes could keep it running w/choke but ruff. Then one day she was running great then...smelled gas in the cabin...then died. Had Canned Air (dust off) in car so figured i'd blow off the dist and coil....besides dust it blew a wire from its connector at coil. After examing the end of the wire it had some fraying ....cut it re connected and my Z doesn't let me down any more... I'm all stock ....points and all....

[cozye]

I SOO Feel your pain. Gotta feeling it isn't solely carb related . I would now look at a short in the dist ....frayed wire / Bad connection...or from coil to dist.

Recently I had the same problem....went on for months....in summer was convinced it was vapor look.....if i waited a while she'd start right up..... sometimes could keep it running w/choke but ruff. Then one day she was running great then...smelled gas in the cabin...then died. Had Canned Air (dust off) in car so figured i'd blow off the dist and coil....besides dust it blew a wire from its connector at coil. After examing the end of the wire it had some fraying ....cut it re connected and my Z doesn't let me down any more... I'm all stock ....points and all....

It would be virtually impossible for an ignition problem to cause the slide in the carb to stick.

[steve91tt]

I SOO Feel your pain. Gotta feeling it isn't solely carb related . I would now look at a short in the dist ....frayed wire / Bad connection...or from coil to dist.

I agree, trouble shooting these old cars can take some time. Spark failure can look like fuel and visa versa some times.

However, in this case, when the car starts acting up I can remove the air cleaner, stick my finger in the carb throat, feel the slide is sticking high, wiggle it so it drops and all is good again. I'm pretty sure that my slide is sticking.

Also, my Christmas gift this year was a Unilite distributor. I set the curve conservatively to 15° static and 33° total at 2500RPM. The car runs about the same with the new distributor. Maybe a little better idle and throttle response on the low end but I suspect that's the result of more timing below 3000 RPM. The slide sticking issue did not change.

ZTherapy asked me to swap slides, domes, springs and needles front carb to back. I made the swap last night and centered the slides carefully with the mixture nuts fully lean. No drama on the swap. The car runs great as before. Hopefully I'll get a chance to put a few miles on it today and test the new setup. If the front carb still sticks then the issue has to be in the bottom half of the carb.

If the front carb still sticks I'll take it off of the car to have a closer look. I'm not sure how else to inspect the nozzle and associated linkage.

[steve91tt]

Just a quick update...

I swapped slide, dome, needle, damper and spring front to back on the 28th. I really thought that the issue was solved as the car drove perfectly until today when the front slide stuck once again on my way home from work.

This proves that the issue has to be in the bottom part of the front carb.

I spoke to Z Therapy and they are going to ship a new front carb out to me ASAP.

[g9m3c]

This service from Ztherapy has been absolutely outstanding. This assures me of my decision to purchase my 260Z round-top conversion from them last year.

[steve91tt]

This service from Ztherapy has been absolutely outstanding.

Absolutely agree.

[steve91tt]

My new front carb came from ZTherapy last night!

They even included a set of new gaskets and a return shipping label for my old carb. Very nice.

It installed and tuned very easily. The car runs great and seems to need much less choke in the morning. I have noticed that this winter I seem to be using way more choke than I did last year.

For this first 10 miles or so in the morning I have gotten in the habit of pushing in the clutch at intersections, if the RPM's drop below 200 then I give it some choke to keep the car running. Once the car is moving I cut the choke and repeat at the next red light until it's warmed up enough to keep going on it's own. This has been taking about 10 minutes of driving on cold mornings (<45F)

With the new front carb this morning was entirely different. I started the car with choke and let it idle for 30 seconds or so (ambient of 35F). I then turned the choke off and it ran perfectly all the way to work! No more red light choke or die dance!

I'm not sure what was wrong with the front carb or whether I have the new setup tuned slightly differently but the car is definitely happier in the morning.

If the slide sticking issue is gone as well I will be one happy camper!:classic: