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  View original topic: Bubbling sound from carb28pic
volks59 Sun Aug 17, 2014 3:21 pm

I'm having a periodic but re-occuring problem on a 36 hp engine with a 28 pic carb. After driving 15 mins upon coming to a stop the vehicle stalls. When I open the decklid I can hear bubbling/gurgling sound from carb. Carb seems to fill up and seep gas from cross-shaft linkage and from gasket on top of float bowl. Car runs beautiful before problem occurs. I've reset float height, replaced inlet valve in the bowl,cleared vent valve. Checked fuel pump push rod travel. Any suggestions would be appreciated

Ojai63dbl Sun Aug 17, 2014 5:20 pm

sounds like it needs a rebuild - but check

1) is float filling with fuel *this will cause it to sink

2) Did you replace the float needle valve - the EtOH in gas seems to gum these up fast

3) is float pin retainer hanging up float

volks59 Sun Aug 17, 2014 5:42 pm

I rebuilt the carb already,new gaskets,float needle valve,mixture screw,accel pump. I've blown all the passages. The float does not have a hole as when I've taken the top off, the float is up. The float bowl has filled with fuel on occasion I assume because the top gasket appears soaked when this condition occurs. Now this carb does not have a float pin retainer as I've seen on other exploded views of a 30 pict. I've checked exploded views of this 28pic carb and there is no retainer.

Ojai63dbl Mon Aug 18, 2014 2:04 pm

hmm


fuel pressure? (anychance you changed pump recently)

I do know that the fuel float needle valve has a washer whose thickness (1mm) affects its cut off point (fuel height)

also did you check valve to see if you can blow through it (shouldn't be able to)- could be defective

take a look here: http://www.vw-resource.com/28carb.html

KTPhil Mon Aug 18, 2014 3:09 pm

Fuel line too close to an exhaust component, boiling the fuel and forcing too much pressure past the float valve?

volks59 Tue Aug 19, 2014 7:20 pm

I have not checked fuel psi yet. I do have the fibre gasket/washer installed on the float needle valve also. Thanks for the link. My fuel lines are routed away from possible heat sources. I do have some small gaps between breast plate and engine tin. Is it possible engine compartment is heating up to cause a boiling situation in the fuel lines without overheating the engine?

Ojai63dbl Wed Aug 20, 2014 5:38 pm

I doubt it is overheating unless your fuel line runs trough fan housing instead of around


But next time it bubbles try this:

tap it with the handle of a big screwdriver and see if it stops.

If it stops the fuel valve is sticking open.

if not top again.

(not a solution to problem but can pinpoint valve is problem

Ojai63dbl Wed Aug 20, 2014 5:48 pm

As I think some think I don't)

Id flatten the fiber washer a bit (or least measure it) and see if that solves it. When I rebuilt mine I used the original as the new one was too thick.

Ive had is crap in fuel line come as line degrades getting into float valve nd sticking it open (usually in middle of nowhere). Blowing line or replacing solves ths

last thought -Did you check the fuel pump filter (assuming original rebuildable style) for grit that might be getting pumped into float valve?

volks59 Wed Aug 27, 2014 12:55 pm

I tried tapping the float bowl with no result when the problem was occuring. I checked fuel psi today and it was 1.9- 2.0 psi. I closed all my gaps around engine tin and will go for a ride.Fuel pump filter is clean, I put a new fuel tank,fuel line from tank to engine when I restored it last year.

Thanks again for all the suggestions.

Ojai63dbl Thu Aug 28, 2014 4:50 pm

long shot - but never know

but could it be our gas cap building pressure - try venting the cap next time to see if you get a rush of air in tank and a stop to gurgling. - your new tank made me wonder if new cap or new sea is keeping tank from venting

better yet borrow a carb from a friend an see if you can isolate it to carb or other problem.



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