desertdatsuns.net

Hi Y'all

Reviving this as I finally got to tinkering this last week or so. To refresh the back story, I had mistakenly put a gallon fresh gas in the tank about a year ago and forgot about the old outdated gas in the return line so soon had polluted the system and stuck the grose jet fuel bowl valves. In taking the float bowl tops off I managed to bend up the floats so had messed up where Z Therapy had set them. Now I know the rotate until they can come off method. I did fill the dampers with the suggested ATF and rechecked that. Then made sure the suction pistons were free - both were stuck a little.

To prep I pulled the plugs and squirted in some 0W16 synthetic and let it soak a day then bumped the starter several times and added more oil and let it sit again, then ran the starter for longer. Then got a gallon of fresh gas and pulled the tank line and hooked up a long hose to the gas can and hooked up the sight glasses to both bowls and blocked off the rear fuel line so as to only run the front carb. It immediately filled the bowl and started leaking out everywhere! SO after cleaning up the mess and straightening out the float and tweaking the actuator tab I had a 1/4" or less in the glass tube so redid it again and got a good level.

Then I got to doing the rear carb and after a bit noticed that the gas was dripping out of the throttle body and was all the way up the sight glass! So I disconnected the inlet fuel hose and stuck some paper towel in the carb throat and finished the rear carb. Figuring that the grose jet had leftover crud from the bad gas of a year ago pulled the front apart and pulled the grose jet and let it soak in gas a day. It did better so it was time for a test fire. A little choke and hit it and she started right up! A very lumpy idle and the front carb fuel bowl level climbed very high and the rear came up to about an inch. I think that the extra pressure from the stock fuel pump might have been the cause.

So I readjusted the tabs again the next day and tried it out again. That front still has too high of a level so I think the grose jet may be a goner? Bummer as they seem to no longer be in production. Is there any better thing to soak them in? Carb cleaner spray?

Also of concern is that while it stayed running until the choke could come off, the idle was lumpy as heck and any throttle was killing it. After releasing the throttle it would idle a hair faster a second or two but just as lumpy. Adjusting the mixture knobs on the bottom and idle screws did nothing. Next up is to pull the plugs. I'm betting they are wet! Think I should get some new ones?

I should mention that it ran fine before I took it all apart to send in the carbs to Z Therapy. I did pull the stock exhaust manifold and installed the MSA 6 into one header and that there seems to be no exhaust leaks and also had a new 2" exhaust run with a turbo muffler at the back end.

I'd sure appreciate any ideas on what to check or on what may be the issue. Many thanks in advance!!!

Randy, I know it's probably really frustrating not knowing for sure what problem you're chasing. I'd be more than happy to discuss by phone with you and get you pointed in the right direction. Call me at 602-312-4038. Randy

Thanks, Randy, for the quick reply. I meant to post early today and just got going on other stuff. I did do some looking around and looked closer at some pictures of rebuild kits and I think I see new needle valves in there! Just gotta find stock somewhere, seems like as it is with a lot of other materials Datsun parts are in short supply. I also meant to look through my car stuff cabinet in the garage and see if I had some old ones or if really lucky some new ones. I feel that until I have that front float bowl running right I'll never get it zeroed in. Also I should dig out the carb paperwork and re-read the instructions. I do wonder which way is a better adjustment on the idle adjustment of the nozzle for our 5300 foot altitude. I think it's mentioned to start at 1 and a half turns. Less air should need less fuel right?

Anyway, I'll putz some more before giving you a call. The offer is very much appreciated!

Any events planned up north for the club coming up? I'd love to drop in on that. It would be in my Subie wagon if I can't talk my son out of his 350Z!

I think your inclination is correct, based on having a similar problem in the past. I would start by replacing the needle and seat in both carbs with new units from Z Therapy. In my experience they can look good but still stick periodically. You'll go crazy trying to trouble shoot the problem till you just bite the bullet. Regarding air/fuel at elevation, I'd try 1 1/2. You may find that's a bit too lean. My 240 is set at about 2 turns and it runs equally well here in Phoenix or Prescott, Flagstaff, not so much.

No current plans for a summer event in Prescott, with the heat upon us, since many of us don't run AC. Your car is so close to being on the road. I'm confident in 1/2 day we could have it totally dialed in. We need to get you mobile again.

Many thanks! I just ordered two rebuild kits from Motorsport Auto in SoCal. I've used them for years. The description for the rebuild kits stated that there was a new valve in the kit. They had a separate listing for the valves but there were none in stock. We should know in a week or so.

Yeah, dang hot up here right now at 99 for a high today and 100/101 for tomorrow... Ugh, you all have it worse though.

Okay, got the carb rebuild kits a couple of days ago and finally had time and nice weather today. I prepped last evening by pulling the front float top out and got the new needle valve installed. The instructions to adjust that didn't make any sense as written so I made my best guess. I found crud in the fuel bowl in pretty good sized chunks and later in the rear one. I guessed that it was the cork gaskets breaking up after so many assembly / disassembly operations. The new kit had thick paper ones which I used. I unfastened the fuel bowl to nozzle hose and blew it out from the nozzle side to make sure no crud got in it.

First go round there was no fuel showing on the front sight tube so I overadjusted the tab. A readjustment and did better the second time. I reset the mixture knobs to one full turn open given the altitude and screwed the idle screws all the way down and backed them out 2 full turns each. I got it fired - it took some starting spray. Still the same lumpy idle and any throttle slowed it down. Oddly after releasing the throttle the RPM's came up. One time it even raced to a very high speed, 5-6000 RPM I'd guess. While idling, any adjustment to either the mixture knobs or idle speed screws did absolutely nothing. So shut it off and let it all cool down. The sight tube level while running was about 3/8" which is low but can't be the reason for what I'm seeing I think.

A check of plugs 2 and 5 and both were wet and smelled of gas. Hmmm... Still, I thought I'd try switching back to the stock needles that Rebello ground down. I watched a video of how to properly set the height in the piston. Same exact running condition! I did a double check of my plug wires to see if they were in the right order and they were. A plug check and they were still wet. Did I gum up the nozzles when I let that old/bad fuel in the system a year ago? Maybe the needle can't seat and too much gas is getting by? Gotta try screwing the mixture knob all the way closed tomorrow and try again.

I know I have a color tune spark plug adapter somewhere and it's time to locate that too. I did look in the distributor and it looks decent. I'll check the condenser too on a capacitance meter. I'll also get it running and shut down, pull the condenser lead and see if it makes a difference. Also to do is check the ignition timing and dwell.

I'll be back when I have results! Please PLEASE chime in, anyone, if you have any ideas! Thanks...

Randy, please post some pictures showing the center link between the two carburetors. I've seen your problem before and it turned out the center link was installed incorrectly so one carb was opening up well before the other. There's a tab that can easily be installed two different ways. Not seeing your car, that's my current best guess diagnosis. Pogden can vouch for this. His center link was installed incorrectly, and as soon as I saw it, I knew what his problem was.

I was pretty sure I had sync'd linkage but took a look anyway. The action externally looked okay and I pulled the suction pistons and double verified. While in there I noticed the front carb's nozzle was down a quarter inch. I was wondering if the old gummy fuel messed with those so pulled the choke cables off and both nozzles were indeed sticky. Then disconnected the choke linkage and pulled each nozzle loose and had a session with each with carb cleaner and many cotton swabs. Thankfully I have a supply of the wooden stick ones. So got those nice and loose but one still likes to stick when installed.

A test fire and that was not the issue. I really didn't think so but it was well worth doing! I did notice that manually pulling the nozzle down like what happens with applied choke on the rear carb made the engine come up to 2-3000 RPM. The front one did NOT do much of anything. Hmmmm.. Later when cool fooled with the suction piston and found it sticks in the fully "up" position in the front carb. With the dashpot off, the piston had no hitches moving in it nor when sitting in the carb. Hmm again.

This morning my youngest son who drives a 350Z these days came over while I dinked around. I made another adjustment to the front float and it ended up bringing up the fuel level a tad so more tweaking to do! My first experiment was to use a flow meter to see how much each carb was pulling and the front carb was about a third of the rear. It sounded better at idle so I gave the throttle a shot and whaddya know, it revved up! My son suggested I try to put the foam air cleaner back on and it also could rev up. Took it back off and adjusted the idle screws to get an even draw and about 700-800 RPM and messed with the mixture nuts. Got it a bit smoother and now she revs up easily without an air filter. WOO HOO!

I'd have loved to do a test drive but I'm running on a gallon gas can as I don't trust the condition of the gas tank as it's sat mostly empty or all empty for years. So I need to find a place that will clean it out up here. I have a lead and some folks to ask. I'd hate to have to take it down to the valley but will if I have to.

Also to do is to wire up the electric fan controller. I had changed out the leaky stock radiator for a Champion aluminum one and dual electric fans. Excited to be able to try moving on!

A sincere thank you for your ideas and encouragement Randy / Randalla!!

Randy, I just was sent a text from a fried in Prescott telling me about the Watson Lake Car Show on August 7 and 8. I'm planning to drive my 240Z up for the show so maybe we can get together and do some fine tuning on your Z.

I'd love that! I'll try to remember to give you a holler as that approaches.