260z motor questions

[Zs-ondabrain]

this makes no sense. You already told us that it sounded nice and smooth when it ran with you spraying fluid into the carbs. Why on gods green earth would you start doing all the unneccesary testing and pulling parts and timing. You have a Fuel issue.....

Sorry to sound like a broken record but you're making a mountain out of a molehill.

Get fuel to the float bowls (Check)

Make sure fuel level is set in the bowls (Check??)

get fuel thru the bowl hoses into the carbs. (check??)

ARE THE CHOKES working??

Are the carb pistons able to move up and down freely?

do the butterflies crack open when the choke is applied??

Are there any Vaccum leaks that may be killing any needed suction thru the carbs??

Process of elimination. eliminate all the fuel problems then move on to Vaccum issues?

think K.I.S. (Keep it simple)

[IdahoKidd]

Hate to dogpile, but it is a fuel issue. My latest 240 had set for 20 years in a garage and it too would initially fire only on starting fluid. Drove me nuts. I discovered I could keep it going by squirting gas into the carbs after it started sputtering on the starting fluid. After several attempts, it started to run on its own but would never start from cold without a lot of starting fluid. Everyone kept asking if the chokes were working and I could see things moving on the sides of the carbs when the lever was pulled so I assumed they were. Turns out the bottom of the float bowl area actually drops about 3/4 inch when it works correctly. Mine was so stuck it didn't show any signs of movement and I didn't even realize it was a moving part. At the insistance of Dave and of Bruce that it did move, I found my spares to compare. Of the 6 carbs I have, 5 had the jet stuck. But the one that did move led to a revelation of sorts. I pulled the bottom of the car and litterally pulled the nozzels apart (they are pressed together originally) and finally got the thing to move up and down. Cleaned them up so they move freely and the car now starts in seconds. Without seeing your situtation, I am betting those jets are not moving and you aren't even aware of it. I'll try to find a picture that may help you locate what I am talking about.

[260 z]

:stupid::bulb: OK, this is my posting to inform all of you who have been helping that YOUR CORRECT. Thank you for taking your time and knowledge to assist me. Although, I am not out of the woods yet, I was able to work on the car today and here is the update.

1)The sucking or vacuum was not checked with the spark plugs out...they were removed after so the compression could be checked. I was also told last night at our local z club meeting that I would not be able to measure or feel the vacuum when the car was just being cranked. You need to check vacuum with the motor running at approximately 2000 rpm.

2) The nozzles were free and moving with the choke cables but the linkage was not opening the throttle plates. I removed the domes and pistons, so I could see the butterfly, and bent the linkage rods so the throttle plates would move to the stopper when the choke is applied.

3) The front carb's bowl, was no longer filling with gas. For some reason the new float valve were hanging up in the closed position. I removed it, cleaned up the old one, and reinstalled it... all is well in Dodge...or Humble.

4) I attached a line to the vents on the top of the carb's bowls. I did this because I was told at the meeting that my needles may be going into the nozzles to far and stopping the gas flow. My DVD is not yet here from Z Therapy, so I am not sure how to adjust that. I put the tube on the vent because when I was setting up the floats, I did this to see if I could get the gas in the bowls to come out at the nozzles by blowing in the tube. When I was cranking the motor, and the choke was pulled, I blow a little on the tube and she started without any starting fluid. I can not keep a steady air flow on the vents and therefor, the motor would only run for a few moments and at various speeds, but it did run on it's own. I will not be able to work on it again until the weekend and by then, I hope to have the DVD.

Thanks again for your help and I will let all know how it runs after the adjustment and final timing.

[Zs-ondabrain]

The Float Bowl Vents are just that. They are only there if the float valve sticks open and the vent allows the fuel to escape the bowl, rather than be shoved into the carb and flood the motor or oversupply it with too much fuel.

On a stock Z, the air filter assembly has 2 inlet pipes for those overflow tubes. The vents allow air flow so the fuel can move freely (kinda like the vent system on a toilet or shower) and if overflow occurs, the raw fuel will dump into the air cleaner assembly instead of the all over the header (exhaust)

So it sounds like the floats or float valves are or were sticky. The fuel level can be brought up by readjusting the floats, and yours may be too low.

Sounds like you're on a roll, keep at it.

Dave

[Jeff G 78]

Before you screw with your floats, PLEASE do some research and make sure you do it right with the proper heights for both carbs. You didn't say what year your 3 screw SU's are, but the '72 3 screw carbs have different front and rear float heights. I made a simple gage which makes it almost fool proof. Without the gage, it was very hard to get them right.

The gage took about 20 minutes to make with some woodworking tools and it makes checking/setting the floats a snap.

[Bruce Palmer]

Unique approach to supplying a known degree of fuel pressure by blowing into the vent tube. I wouldn't drive around with an air nozzle hooked up to it but for what you're trying to solve, it's pretty darn resourceful.

On the float settings. Unless the kits you bought had two different lengths of needles and seats you'll have to adjust both float levels the same height regardless of the length of the standoffs.

Oh, and the needle in an SU carb will never shut off the flow of fuel. OD of the needle at the base is still smaller than the ID of the nozzle.

Press on. If captured behind enemy lines this agency will disavow any knowledge of your existance or whereabouts.

[260 z]

:stupid::)Monday was the first time I could work on the car for some days. With the help of choke cleaner I was able to get the car running but only at 2000 plus RPM. I spoke to Steve per Bruce's recommendation and he said all that I had done was correct but I needed to straighten out the choke linkage since I was unable to keep the car running under 2000 RPM. When I did that, I could not get the car to start again so I went back to the beginning to confirm all the settings. I also recalled Steve to see if there were specific amounts that the butterfly should be open at choke and idel...he said there were not and in his closing statement said ..if you have compression, spark, correct timing, the carbs set like we spoke and good gas it should start and run. When he said "good gas " it got me thinking about the gas. When I got to the car Tuesday, I disconnected the gas line from the tank and pumped some of it into my clean " mason jar ". What did I see but a mixture of 80% gas and 20% water !!!! I went to a different gas station and bought two gallons of gas and connected it directly to the mechanical pump's inlet. After purging the lines to the carbs and draining the carb bowls, I reconnected the coil and tried to start the car. She didn't turn over three revolutions before it was running on it's own. NO SPRAY CLEANER INTO THE CARBS NOR POSITIVE PRESSURE TO THE BOWL VENTS TO GET IT RUNNING. I guess that the 20% water was to much for the car to start or idle considering the small volume of fuel going to the cylinders. It ran about five minutes at 1200 RPM on choke and when I took it off choke, it would idle at 800 RPM but it was rough. I tried to balance the carbs ( for the first time ) but went through the two gallons of gas in about thirty minutes?? Is that excessive, and if so, what needs to be corrected ??

[Zs-ondabrain]

You didn't go thru 2 gallons in that sort time. When you connect the feed line to a gas can, WHERE is the return line connected to. If it's still connected to the return line that goes back to the tank, THAT's where the fuel went.

The Fuel pump pumps more gas than the Carbs need, the return line takes the excess and dumps it back intot he tank. So at idle or low consumption speeds (RPMs) the fuel is merely circulating thru the tubes, feeding the carbs and returning the fuel to the tank. This is also a good way to keep cooler fuel in the lines, when they sit over the exhaust like they do.

So if you're gonna test the motor with a small gas tank, run the return line into the same tank, you'll find it lasts a lot longer than the other way.

Sounds like you're on a roll though.

Dave

[260 z]

Thank you zs-ondabrain. I knew about that return line to the tank but did not think about it until you reminded me. That makes me feel better and confirms that my mechanical pump is putting out a good volume.

One more small step for this z restorer.

[Zs-ondabrain]

I just happened to stumble upon the answer. I was working on "73240"s 240Z the other day and had to explain the same thing. He is using a 1 gallon can to get the car running. Though he had removed the return line rubber hose and the overflow was going onto the ground. So your question was in line with what I had already dealt with once this week.

Step by step, Little here and there,

Dave