Crush your float?
 

Hi All,

I need some advice. Tonight I am going to rip my webers off to check the floats. But before I get there I was wondering if anyone knows what the symptons of crushed floats are in webers (the kind of crushing you do by forcing compressed air into the carbs)?

Cheers,

Daniel

I don't think you have to worry about that if you have the original brass floats in there. They are pretty beefy. You'd have to use some serious air pressure in order to damage them.

-Wayne

Thanks Wayne.

I dont know what is in there. I guess the real question goes something like this.

* Car was running good but could use a tune.
* I took it in to the mechanic. When I picked it up it was stalling at idle (had to keep the foot on the accelerator). Popping as if running lean and just general crappy.
* I rang the mechanic the next day who told me he blew out a lot of gunk and it sounded like the gunk was back. He suggested the fuel tank needs a clean out.
* This morning before going to work I opened up the fuel filter, it is about 5 months old, and it was clean as a whistle. So I rule out gunk from the tank.
* Today I did a bit of research and found putting compressed air in the carbs is a bad idea. Now I am wondering if this is the problem.

Other information:
* If I keep the revs high it doesnt seem to have a problem.
* The carbs were rebuilt about 6 months ago, so it may not be metal floats.
* At that time I spent $4k (!!) trying to track down a similar behaviour with the now old mechanic. This is how I ended up with rebuilt webers over my old Zeniths. As it turns out the problem was non resistive plugs, lines, coil etc. Once I put the resistance back in - BAM, problem was gone.
* Last night I also did a plug change at the local motorsport store, as again I noticed the new plugs from the tune were non resistive. Sadly this wasnt the fix.

Any ideas would be appreciated, later tonight the carb comes off and I will take a look.

Float levels messed up by air maybe? Depends how much pressure of course.. but if he thew 180psi down its throat its possible.. its also possible he is correct and you have more gunk in there.. not from the tank. Just some thoughts.. carbs are easy in my book.. take em apart, clean them, set the floats.. gasket kit, assemble.. tune.

I agree but could you bend the small levers soldered to the floats with air pressure?

Well I have just cleaned up from taking one carb out and apart.

Looks like the mechanic was partly (mostly) right. Blame my distrust on the previous experience.

The prognosis is this, the floats are brass and they look fine. They swivel on their hinge fine too.

What I did happen to find, without looking very hard at all, was a big (relatively) black paint chip from the air filter housing which is attached to the carb body (the housing proper is plastic). Inspection of that part shows paint peeling... 1+1 seems to equal 2 here.

So I guess that is what is in there. Good news is I dont need to clean the tank, bad news is I need to clean the carbs and (re) rebuild them. That isnt all bad news, as I will do it myself and learn more about the carbs and how to set them up.

So this doesnt happen soon after rebuilding them, I will get the housing stripped and powder coated. Should I stay with black or go with red or something?

Also there are quite a few fuel leaks from the carbs, so here is my opportunity to right those wrongs.

For now I guess the car will be of the road for a week or two while I wait on parts and tools.

You could strip and paint the housings with POR 15 Paint and then top coat with chassis semi gloss black.
It really is a great product. Guaranteed not to peal, crack or flake off.

"Paint supplies" at the end of West lakes boulevard has the full range of POR 15 products. (no affiliation)

Sounds about right.. this is an easy one. Which carbs? webers I have all the gaskets except the accelerator gaskets... if u want them I'll sell em real cheap.. But the accelerator gaskets and diaphrams are a common problem.

EDIT: accel pump gaskets... you know what I mean.. the things with the diaphragms in them.. they usually leak when the car has been sitting.. so what I have is probably not all you need.. and if you need a source let me know.. seems like if I remember our host doesnt have them or something.. I forget but ended up getting them somewhere else.. maybe significantly less.. forgot.. was 6 months ago

Black paint chips in carburetors.

There are two types of air filter assemblies used in 911s with Weber and Zenith carburetors and MFI. I include MFI because some of these parts interchange with carb air filter assembly.

There is a steel version and there is a plastic version. The air filter assembly ‘cups’ at the top of the carburetors (and ’69-’71 MFI) are always steel. There is a combination of steel ‘cups’ and plastic air filter assembly in ’71 911 and 914-6.

Steel vs. plastic: there are pros and cons to each.

Plastic air filter assemblies are commonly damaged with carb intake fires. You typically don’t know this even happened until you see the underside of the seal fit to the ‘cup’.

Steel air filter assemblies can rust in the double panel area where there is the baffle for the breather. This generates rust particles and paint flakes that end up on top of the carburetor and on the bottom of the ‘cup’. These particles and flakes typically get into the main air jets (screwed into the carb top) and idle air jets (pressed into the carb top).

Most of this debris goes down the intake and is ‘eaten’ by the engine. Anything left ends up in your muffler or out the tail pipe. Worst case is a hard piece of rust ending up alongside the top of a piston, scratching the cylinder.

Symptoms of the restriction in the idle air jet is commonly dropping a cylinder at or off idle. Symptoms of a restricted main air (correction) jet are commonly dropping a cylinder under load and higher rpm from too rich on that cylinder.

Only after these particles and flakes have been blowing about for a long time can they find their way into the float chamber. Small pieces can find their way down the air correction jet and emulsion tube. Some get down the float chamber vent tube.

Once in the float chamber, idle jets are usually the first to get plugged.


At this age, I suspect it is not uncommon to find a PO has painted the inside of their old air filter assembly and ‘cups’. A great deal depends on the surface preparation, painting technique and type of paint. I’m sure there are some (rattle-can?) that flake off.


Back to the steel vs. plastic debate.
I prefer a well maintained steel version for fire resistance.

Best,
Grady

Sorry,
I was thinking of the end of Animal House, where they wreck some floats.
Carry on
eric

Key to proper Weber operation is among other things fuel pressure and fuel level in the float bowls.
3.5 lbs fuel pressure is correct and should be verified.
Fuel level is best obtained with a float gauge attached to the float bowl while the engine is running.
Pelican part #PEL-PMO-004, $34.
There is more, but these must be addressed first.

Adelaide901,
A few questions come to mind,
What size motor? Any mods?
Weber carb type? Venturi size, idle jet size, main jet size, air correction, emulsion tube?

The settings of the idle fuel screws and idle air screws can give us an indication of how the carbs are setup.
How many turns out are each idle fuel screw?
How many turns out are each idle air screw?
Sounds like the engine will not idle.
I couldn't pay any mechanic for tuning if the engine wouldn't at least idle.
There is more.

Grady - great advice. Thanks.

I have a plastic and metal housing. I use the plastic one because it is a lot lighter. The cups are the culprit, there is clearly paint flaking off on the inside. It looks like it has been floating around for a while because it did get into the fuel system. The car would run fine under high revs so yes the idle circuit was the first to go. I will have the cups powder coated when I rebuild the carbs.

Rebuild kits and float gauge is coming - cheers. It will take about 2 weeks to arrive so in the mean time I get to rebuild my brake system.

Doug - when I took the car in it wasnt running great but not too bad. Now I think I will invest the energy to learn about webers so I can do it for myself in the future. As with anything, the time and energy required to do it the first time is high, but the payoff every time after that is higher.

Learning about Webers and whatever else catches your fancy is great.
Part of the Porsche experience.
There is a great deal of info here, as well as folks like Grady that know this stuff forward and backwards.
In the meantime if you have the time, get the info on the various Weber components to be sure you are working with the right size for your engine.
Enjoy,

this is what I found after a float sticking problem.

http://forums.pelicanparts.com/porsche-911-technical-forum/406747-what-happened-my-weber-floats.html

sc_rufctr - so many times I have been past that paint place without the appropriate excuse. Now I have one. Thanks for the tip.

haycait911 - OUCH! That is what I thought may have happened to me when I was researching the other day.

Check the throttle shafts (front AND rear) for play while you're at it.

Adelaide - heres a good thread for weber tuning...

http://forums.pelicanparts.com/porsche-911-technical-forum/67957-weber-rebuild.html

Thanks Cam. Was that your 911 at Mallala a few thursdays ago, or was that just an imposter?