Idles, But Sputters & Stalls @ Slight Throttle-up

[72' 240]

The problem first manifested after it sat for about 3 weeks. I took it to dinner one evening and it uncharacteristically stalled at a light. After dinner, it stalled again, but was very hard to start back up. I later probably fixed this problem when I was chasing the follow-up problems when I replaced the condenser.

At this point It will start like I am switching on a light. It will also idle ( Fairly smoothly at that). It will not even consider a slight throttle-up. It chokes very quickly as if to stop, but as I return the Throttle to idle. I idles smoothly again. I cannot even idle-up at the set screw. It's crazy.

Below is a list of the actions that I have already taken, and parts that I have thrown at this issue. Thank you for your help.

*New Mallory Distributor (ran 6 months well with this same Dist.); I have even replaced the stock distributor with no change in situation.

*"Running" a sweet New L28 From Motorsport in a clean 72' with stock SUs

(Cleaned and polished, new gaskets needle/seats etc.

*New coil

*New Points( Set at Approx. 22 thou.)

*New Cap

*New Condenser

*New plugs

*New Rotor Button

*New Cap-to-Dist. Wire

*New Fuel Filter

*New Fuel Pump

*New rubber lines, even at the bowels (Also from Motorsport ($$$ wow!)

*New external Resistor (The coil is set-up for the external- wiring was easier)

I've:

-Drained the Tank

-Run a bypass line to the engine from a large tank of high Octane

-Checked fuel flow to carbs

-Blown all lines out, even to the tank

-Cleaned the windshield

-Removed both carbs and cleaned thoroughly

-Called Motorsport Tech folks (O.K.)

-Called "Pierre Z" in Calif. (suggested that I lower point gap to... 16 thou!)

(Ruined a new set of points, didn't help the condensor any either)

(Mallory tech got me back to 22 thou.)

-Removed the exhaust at Manofold joint to make sure that the air

flow/exhaust was not impared.-Not Helpful either...Just noisy!

-Obviously I've kept an eye on the dempner oil.

I am leaning towards fuel levels in the bowels... I feel like I've leaned about every way possible... WoW!

I will take any and all suggestions.

Thanks guys.... & gals (my daughter is sitting beside me and she also likes our z's).

[AxtellZ]

Huh.

Sounds like you've addressed all you can think of. Has the carb adjustment been toyed with? Does the choke on/off change anything?

Have you checked the floats in the carb bowls (not bowels, eww...)?

Seems unlikely both floats would crap out at the same time..

How lean/rich are/were they set?

Keep us informed,

Jeremiah

[72' 240]

Jerimiah, thanks for your thoughts.

Yes the carbs were "adjusted" by me (I know what you're thinking). I have a vacuum air flow meter, so that is easy enough. But the mixture, that's another issue all together. I restored "default" settings regarding the Jet height within the venturi. The front jet is, despite quite a bit of work and lubrication, a little hesitant to pop right back up as the choke is released. I do believe that the mixture is still a bit on the rich side. Having been around grossly rich running cars, I've noted that they are usually running, they smell bad, and exhaust black, but though poorly, they usually do run don't they?...?

I wonder about firing order, but I,ve checked that until I can't see straight anymore. It is such a helpless feeling to see this car go from a vehicle I thought nothing of driving on a 1000 mile round trip to the N.C. Mountains, to this useless state.

The floats float, well they seem o.k., and undamaged or "gas logged". They may not be allowing enough fuel into the bowels(scratch that) ...bowls to allow throttle-up, only idle. It is very hard to check them out. I have mounted the bowl caps on glass jars and checked the needle/seat operation, But measuring fuel left in a bowl after fighting off one of those caps while taking into account that there will be a certain amount of fuel clinging to the float as you remove it as well... Oh well.

[Jayru]

I had a very similar condition to yours without the stalling. It turned out my alternator was on the way out. It would idle fine, but not rev past 3000~3500 break up and almost stall. The battery was low and the alt was not charging it, so it lost electrical power and starved the ignition of juice.

I looked at everything like you did and found nothing. I didn't finally figure out the problem untill the alt took a $^!# all together. Hope this may help.

[AxtellZ]

Hmmm

So, if you pull the covers from the float bowls, there is plenty of fuel in both? Fuel is getting through the filter at the banjo fitting, and through the needle/seat assembly?

It sounds like it could be way too lean? When you try to apply any throttle, the added air coming in leans it out so much it stalls? Will it rev with the choke applied?

How many turns out do you have the mixture screws at the bottom of the nozzles?

This is one i wish i could go "hands on"! Do you own the Ztherapy carb tape?

Just reread what you wrote- as far as "default Jet Height"- whaddya mean? You mean adjusting mixture, or how you set the needles?

Keep plugging, we're gonna fix this!

[72' 240]

Thanks Jayru,

I have had probs in the past also with alts. As you know 50 AMPS is just not enough. As a result, I have been running a "successful" zx internet upgrade. I have been exceptionally pleased with the upgrade, but through all this time of testing, I may have Asked too much of it. I'll look that direction for a while. I'll pull it, and run it down to the shop and have it tested.

[72' 240]

Jerimiah,

Thanks again for putting your thoughts to the problem. By the way, what a great Family/Z photo. Atleast you have your priorities in order. I believe that the car was on your right side...

Now Back to MY woes.

First, the "default" setting I spoke of was taken from Clymers "Datsun 240-280z & zx". "1970-1979 Shop Manuel"; "A152 Clymer Publications" Page 98; bottom right side of page. Jerimiah, they give a pretty sharp diagram "Figure 16" on Page 99. It really seemed helpful, as they describe the proper position of the nozzle to be 2.2mm or 0.087 in below the "Jet Bridge".

That seems to be the starting point from which they feel that proper mixture is reached. I still seem to blacken my plugs a bit, so I don't know.

Ah yes, I almost forgot... I LOST my copy of "Just SUs"--- wow.

Keep thinking! I need the help!

Thanks,

Frank

[AxtellZ]

Try Bruce Palmer..

http://www.classiczcars.com/forums/showthread.php?t=10207&highlight=bruce+palmer

He is the Ztherapy answer man. My Z's are out in 14F cold, waiting another 2 months, and my mind is going blank... Try a private message to him if he doesn't see this thread.

[beandip]

you can reach Bruce at ztherapy.com Have you checked for vacume leaks? also the vacume advance , have you tested it ? To check for vacume leaks , with the engine running at idle spray some carb cleaner where you suspect a leak and if the engine changes RPM you found it. Try removing the vacume line to the brake booster and caping the fitting. The extensive list you provided cover about everything I can think of . What did you use to clean the windshild ? Sorry couldent reZest. I doubt the floats are a problem , especially at idle , if there is any fuel in there at all. As for the choke sticking did you use the proper fuel line , if the line is stiff it will bind the choke and it will stick resulting in a vary rich mixture. But this wont account for the lack of RPM . I don't remember you saying what you set the timing , 10 BTDC ? NGK plugs ? Run a ground wire from the engine to the body or frame. keep us posted on this . Gary Bruce's phone 503-587-9800

[Curtis240Z]

If it is your alternator/battery, try turn on the headlights when you are idling and see if the symtoms worsen.

[72' 240]

Thanks folks for all the suggestions. Jerimiah, man thanks for the tip on contacting Bruce. "Beandip"... Dotto. I've grown optimistic at the thoughts of running a few tests on it in the morning (Sat.). Beandip, 10 deg. is about right, and I've run NGKs aswell. The carb cleaner is a great suggestion. It will be easy enough- thanks curtis. I've got a bit of that around the shop; I'll try that. I just feel real optimistic about the alt. I have a "new" one in a box in the shop, so I'll slap that on at some point as well.

Sorry for all the excitement, but it is amazing how stressed it makes me knowing that for every day that car sits, the problem gets no closer to being solved. I am sure many of you have felt that way before. A small yet ever present reminder that something "just ain't rite" as some of my fellow southerners might say. My wife and family are patiently and (somewhat) silently waiting for this to end as well, so thanks for the help... We are making great progress I think!

Thanks again-

Frank

[72' 240]

Well, add the fact that my alternator checks out at 15volts(+), and the problem still remains. I wish I had better news, but the alternator was not the culprit either.

Hmmm, two carbs failing at the same time doesn't seem likely. I guess at this time, all I can do is ease-up on the float levels a bit, and see if I'm just starving the thing. Any more ideas out there? As AxtellZ said, "we'll fix it if we stay at it.

Don't feel bad; I've been bugging a friend here in Birmingham half to death with this, and he has few new ideas. The difference is that he is known all over the city as "The Car Doctor", and used to be heavily involved in NASCAR many years ago. He has a repair center close by. Some may ask why I don't just leave it with him... Well, at this point I feel alot like I should, it's just that driving it over at "idle speed" would be a bit tricky. The bigger reason is that I will be admitting that I can't work through it myself. Ugh!

Sorry that I couldn't report that I drove the thing today. It was a great day outside in Birmingham today; sunny, and 70. (Sorry Jeremiah!)

72 240

At Large

(with no wheels!)