Zenith mystery- begging for help.....

[blackbird225]

First off, I have searched all posts, and posted this question before with no replies. Others have posed this question, and they were not asnwered.

Ok. 70T with recently rebuilt zeniths
With normal bowl plugs in place , the carbs don't overflow, but I am having a hard time tuning.
I bought the p266 float level adjuster.

Left Carb Bank Bowl-1 adjusted perfectly fine
" " " " 2 with the tool in place, the fuel pours out of the brass tube coming out of the top. Put the little cap back in, no overflow !!! These are new float needles.
I am so frustrated...
One more thing, there is always a little fuel in that little resevior where the Air correction jets sit. Only in the bowls that overflow during adjustment.

Remember , the floats all float, the hinges work fine. And it doesn't leak with the little silver plugs in place.

Please PLEASE tell me that you have seen it before and its easy to fix.

Thanks

Michael

[Grady Clay]

Michael,

Are you sure the complete ignition system is working properly? CDI, connections, grounds, coil, wires, plug connectors, timing and spark plugs?

1st: Fuel pressure. You need to know that there is proper fuel pressure all the time. Use 15' of Porsche/VW/Audi/MB washer hose to your fuel pressure gague. You want to be able to see it while driving and while tuning.

2nd: Fuel flow. You want to know that the pump will flow the required quantity all the time and to every float chamber. Make yourself a filtered hose that returns the fuel to the tank while you watch. You can measure the liters-per-minute with a calibrated container and a stop watch. A common ailment is the filter screen in the tank won't allow full flow all the time. Pull it out and clean it. How old is the fuel pump?

Now that you have those two veriables under control, deal with the carbs.

3rd: Are the carbs perfictly clean? There are a lot of "pressed in" jets in these carbs. Are they all clean and pass fuel/air? Put air and "brake clean and carb clean" both directions through every oriface. One of the most frustrating cirmcumstances is that the cleaning loosings flakes that then block the orifaces during fuel/air flow but drop out of the way when you inspect.

4th: Do all the needles and seats properly pass gas when full flow and yet seal perfectly when the float chamber is full? One of your statements is: "... the fuel pours out of the brass tube coming out of the top." That indicates that the needle&seat isn't sealing when the float chamber is full (it then overfills and pours out.) That is a major problem that needs to be fixed. It can be caused by too high fuel pressure, dirt in the system that gets in the N&S, or a defectve needle & seat.

Please report what you find.


A BIG issue is your personal safety with all this gasoline around. Be careful! We don't want to visit you in some burn ward, or worse.

Best,
Grady
gradyclay@hotmail.com

[blackbird225]

Grady...
The car runs strong at med-high rpms, but a rough idle with pops. I have spent hours with 3 manuals trying to get the carbs to match up. The one thing I always skipped was the float height. So I bought the tool that checks the height. Then I started having this wierd overflow problem. Another guy posted on this topic and he said that his fuel pump would make a higher pitch when it started to overflow. Mine does this too. Maybe it is fuel pressure, but why then does left carb bowl-1 calibrate perfectly every time? It is a new fuel pump. A cheapo napa fuel pump. The carbs are perfectly clean from top to bottom. When I rebuilt them, I didn't remove the pressed in brass parts, but like i said, the car runs pretty nice. I am pretty sure that I am getting fuel to all the right parts. Right bewfore they went into the car, I blasted carb cleaner thru all of the holes, and never one blockage.


I just wish this would go away...

[andrew15]

Try going back to you old needle valves.
When I put in new ones in my Webers, I found that they wouldn't seal off and would allow the fuel bowl to keep filling slowly until overflow.

Not sure of the Zenith design, but could the plug on the bottom of the float bowl create a sealed environment, somehow pressurize the air in the float bowl and thus prevent overflow at low pressures - but with the p226 tool in - no pressurizing thus overflow?

Regards,
Andrew M

[Chrisrad99]

A fuel pressure regulator appears to have solved my Zenith overflow problem. I used an regulator that is adjustable up to about 5.5 psi - they are available at Kragen here in California for about $16. This car has been sitting for about ten years, so there may be other issues with the fuel system and perhaps the fuel pump. Perhaps one of the experts would know if there is any pressure regulation within the fuel pump, I could not find anything that indicates now pressure is regulated (there is a diagram in the factory manual).

Be very careful, since gas that spills from the Zenith overflow tubes collects in the cavities in the top of the carb. If the engine backfires, these will catch on fire - this happened on my car!

[yelcab1]

I don't have zenith, I have weber on my 308GT4, four of them, and double barrels each. I had lots of problem synching them and also an overflow problem which turned out to be float valves (not in your case).

My comment is I tried to solve the problem with a Napa fuel regulator and it almost burned my car down. Since then, I have not trusted Napa fuel parts and would not put them on any of my car. So, your cheapo Napa fuel pump may or may not be the right one.

[blackbird225]

Andrew is definately right. The bowls that are flowing over when the tool is in must be because there is a pressurized environment when the plug is sealed in place. The feul simply fills all the way up to the tops and a seal keeps it from gushing out... but the tool allows pressure to equalize and let the fuel pour out...
Sucks to be me in any case. Looks like a new fuel pressure regulator.
The sad thing is this. I am not too sure where the fuel pressure regulator is on my car.
Michael

[andrew15]

If it's the original pump, I think it is internally regulated. The bad needle valves on my carbs leaked regardless, so your pump may be just fine. It may just be the valves.

Whoops - just noticed the NAPA thing - if the fuel pump was replaced, you may not have any fuel regualtion at this point and may be sending too much pressure to the needle valves with some of them being overpowered.

Personally, I installed a Carter pump, Holley fuel regulator and a pressure gauge to keep an eye on things. Works great and I've never looked back.

Regards,
Andrew M

[andrew15]

So in short:

- Get a better fuel pump
- Regulate the flow to the carbs
- Don't go cheap
- If that doesn't work - try swapping the needle valves back to the old ones (new ones may be defective - but probably just overwhelmed with pressure from the currently unregulated flow)

At least that will get you started

Regards,
Andrew M

[Chrisrad99]

FYI

I have found that the overflow problem on my Zenith carburetors was caused by an overpressure from the fuel pump. The strange thing was that the over pressure was only temporary, after about four minutes the engine was starved of fuel and subsequently sputtered, lean backfired before dying out.

The problem was traced to a blocked return line at the gas tank. This fuel pump has three connections - the gas line, return line, and the pressurized fuel line to the carbs.

If your car as been sitting for a while, the elbow in the return line could be blocked with rust or debris. This had to be drilled out in my car, the coat hanger could not even get through it.

Good Luck

[71T Targa]

There was a recent thread about the float being blocked by the float level adjuster tool. Apparently the tool was going in to the float bowl farther than the plug, and was keeping the float from moving. You might want to check the thread depth of the bowl plug compared to the float level adjuster.

[blackbird225]

hhehh That was me who posted the fix for this! LOL
I forgot to come back to this thread and clear that up.
Thanks so much for taking the time to reply. Thats what makes this board so awesome!

Now, i need to get my Bosch distro and then msd and coil.....
Michael

[71T Targa]

That is too funny. I didn't go back to the other thread. Just remembered reading it.

[911ctS]

Originally posted by phred68
There was a recent thread about the float being blocked by the float level adjuster tool. Apparently the tool was going in to the float bowl farther than the plug, and was keeping the float from moving. You might want to check the thread depth of the bowl plug compared to the float level adjuster.

Very true. Im not sure on the # of the float tool i use but i certainly have to put a little washer on the end to space it away, or it will keep overflowing. You dont want it threading in too far or this will happen on Zeniths.