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> Carb issue's
mb911
post Nov 9 2018, 09:00 PM
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I have some clean (so I think) Weber 40s for my engine.. Trying to get the engine running. I can get it to fire and run 5-10 seconds and it dies out.. This is not off of the idle Circuit.. I have little experience with webers and some experience with zenith 40 tins.. Mostly efi on my 911s and 914s.. I put new gaskets and correct new jets in everything.. What would be your suggestions as first thing to look at? Accelerator pump squirters on 456 bank don't work as the bowls empty and don't refill ..

Love to borrow a set of carbs to set timing and refigure out the carbs but not sure if that is possible.

Any Weber carb experts?? The new ones are looking pretty enticing...
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mb911
post Nov 9 2018, 09:01 PM
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Mark Henry
post Nov 10 2018, 07:01 AM
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Likely the float valve (grose jet) is sticking , hole in the float (waterlogged), incorrect shims under float valve(s) and/or float tab is incorrectly bent.
Never use compressed air on the float or fuel inlet, it will destroy the floats.

https://www.piercemanifolds.com/category_s/316.htm


There are tools you can shop make for setting the floats, but this below is faster/easier.
http://www.sierramadrecollection.com/Carbu...914-p16605.html
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mb911
post Nov 10 2018, 07:53 AM
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QUOTE(Mark Henry @ Nov 10 2018, 05:01 AM) *

Likely the float valve (grose jet) is sticking , hole in the float (waterlogged), incorrect shims under float valve(s) and/or float tab is incorrectly bent.
Never use compressed air on the float or fuel inlet, it will destroy the floats.

https://www.piercemanifolds.com/category_s/316.htm


There are tools you can shop make for setting the floats, but this below is faster/easier.
http://www.sierramadrecollection.com/Carbu...914-p16605.html



Ok great thanks good place to start. I do have that tool so that will be helpful..
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914forme
post Nov 10 2018, 08:16 AM
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? about the float setting tool.

you screw it into the float bowl and it has a vial on the side that lets you see the level of fuel in the bowl.

If that is correct, I guess I know why PMO installed site glasses on theirs.

Is the vial plastic or glass? Wondering about it degrading over time.

And Ben at least it is out of the car where you have full access to the carbs to fiddle with them.
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IronHillRestorations
post Nov 10 2018, 08:51 AM
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I'll 2nd that it sounds like improperly set/sticking float valve or fuel delivery problem on 456 carb.

I have a fuel level tool if you want to borrow it Ben
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Mark Henry
post Nov 10 2018, 09:29 AM
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QUOTE(914forme @ Nov 10 2018, 09:16 AM) *

? about the float setting tool.

you screw it into the float bowl and it has a vial on the side that lets you see the level of fuel in the bowl.

If that is correct, I guess I know why PMO installed site glasses on theirs.

Is the vial plastic or glass? Wondering about it degrading over time.

And Ben at least it is out of the car where you have full access to the carbs to fiddle with them.


It's plastic, you don't leave it on after set up. The sight glass has a open top and would be a recipe for disaster if you leave it on.
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pneuhyde
post Nov 10 2018, 01:01 PM
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QUOTE(mb911 @ Nov 9 2018, 08:00 PM) *

I have some clean (so I think) Weber 40s for my engine.. Trying to get the engine running. I can get it to fire and run 5-10 seconds and it dies out.. This is not off of the idle Circuit.. I have little experience with webers and some experience with zenith 40 tins.. Mostly efi on my 911s and 914s.. I put new gaskets and correct new jets in everything.. What would be your suggestions as first thing to look at? Accelerator pump squirters on 456 bank don't work as the bowls empty and don't refill ..

Love to borrow a set of carbs to set timing and refigure out the carbs but not sure if that is possible.

Any Weber carb experts?? The new ones are looking pretty enticing...


I had a similar issue when I converted from EFI to carbs and finally found that I was only energizing the electric fuel pump during the "Start position on the ignition switch and when it moved to the run position the electric signal stopped because they are different circuits and I had not wired it properly.
The bowl filled during the start but as soon I started driving down the road the bowl would empty.
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sixnotfour
post Nov 10 2018, 01:49 PM
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pump em a bit ..no choke...needs more fuel when cold
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mb911
post Nov 10 2018, 02:59 PM
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Ok sounds like a plan.. Gonna check levels and try again. Next step per Paul @performance orientated is clean the idle Circuit passages amd remove the lead plugs..
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Retroracer
post Nov 10 2018, 07:08 PM
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The float level indicator tool is a good place to start.

I notice on your bench test jig you have an electric fuel pump but no obvious pressure regulator. Have you measured the fuel pressure as presented to the carbs? The Webers (and Zeniths for that matter) are expecting 3-5 PSI there - higher pressures can overcome float needles and flood the chambers.

- Tony
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mb911
post Nov 10 2018, 07:45 PM
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QUOTE(Retroracer @ Nov 10 2018, 05:08 PM) *

The float level indicator tool is a good place to start.

I notice on your bench test jig you have an electric fuel pump but no obvious pressure regulator. Have you measured the fuel pressure as presented to the carbs? The Webers (and Zeniths for that matter) are expecting 3-5 PSI there - higher pressures can overcome float needles and flood the chambers.

- Tony



Tony I am not running one as of yet. This pump only provides 3.5 psi so thought I was good to go.. I will probably add a regulator as well better safe then sorry..
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porschetub
post Nov 11 2018, 12:14 AM
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QUOTE(Retroracer @ Nov 11 2018, 02:08 PM) *

The float level indicator tool is a good place to start.

I notice on your bench test jig you have an electric fuel pump but no obvious pressure regulator. Have you measured the fuel pressure as presented to the carbs? The Webers (and Zeniths for that matter) are expecting 3-5 PSI there - higher pressures can overcome float needles and flood the chambers.

- Tony

Yes but it will still run if not rather badly with excessive fuel pressure,sounds like the primary circuit isn't working ,even in basic setting the motor will start if the setup is close.
What do you have the mixture screws set to? pull the air cleaner and see if you have fuel enritchment from throttle pumps.
Good luck Ben.
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mb911
post Nov 15 2018, 07:42 PM
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Running better now.. Good oil pressure so very happy about that.. I need to really tune the carbs.. Seems like I have the firing order wrong so gotta check that.. 1 step closer..
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mb911
post Nov 16 2018, 05:16 AM
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https://m.facebook.com/groups/4020297998314...249687078399000
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mb911
post Nov 18 2018, 02:22 PM
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Float levels have all been set for a base line(not running) I would run the fuel pump and noticed that there is gas weeping from gasket mating areas and believe that is a fuel pressure problem. Pmo fuel pressure regulator should be here today..
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mb911
post Nov 19 2018, 06:11 PM
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It's running well now..

https://www.facebook.com/100025285101338/po...98319411020893/
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Retroracer
post Nov 19 2018, 08:05 PM
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NICE!

- Tony
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mb911
post Nov 19 2018, 08:06 PM
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It was really just back to basics..
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