Carburetor Dillemma

[bgsengine]

Recently had a Tecumseh H50 come in - gas running out the carburetor.

Simple, right?

R&R Carburetor, clean, flush out fuel system, has new fuel lines 6 months ago, closer inspection revealed a brand new OEM Tecumseh carburetor on it. Tested float, R&R and replace float needle & seat. Put back together, andd lo and behold, it still has gas running through it.

Thinking maybe I didn't do something right, took it back apart and bench tested (again) - weight of the float holds 5 PSI pressure.. Baffling - it should not be leaking gas... close inspection of everything and even tried a new float.. same problem.

Sat down to think it through and study the carburetor again... AH-HA! .. I will give you one more hint - It was a Snow King (snowblower) carburetor , although it was on a utility (chipper/shredder) engine.. and the solution was to un-do something the other shop did (thinking they were preventing future problems)

Any guesses as to why this pristine, clean, Tecumseh carb with new float, needle and seat (and holds 5 PSI pressure on bench test) still allows gas to run through the carburetor?

[bluemower]

interesting problem, not real familiar with all the tec carburetors.

some of these had an anti vibration spring on the needle. Also problems with venting could exist.

[creia]

Something to do with the primer bulb or primer bulb fuel circuit? (Am I on the right track?
Michael

[bgsengine]

Something to do with the primer bulb or primer bulb fuel circuit? (Am I on the right track?
Michael

Ding! Ding! .. Shows you're thinking.. I'd call it "pretty warm" for a guess... any further thoughts?

[Skywatcher]

Hi BG

Going on what I've read so far, I'm going to say a non vented primer bulb so float bowl pressure can't equalize with atmospheric, therefore pushing fuel up through the main nozzle or the load circuit air bleed. I've seen this happen on a Tecumseh lawn mower engine. All the best,

Sky

[bgsengine]

Hi BG

Going on what I've read so far, I'm going to say a non vented primer bulb so float bowl pressure can't equalize with atmospheric, therefore pushing fuel up through the main nozzle or the load circuit air bleed. I've seen this happen on a Tecumseh lawn mower engine. All the best,

Sky

Nailed it - sort of - the previous tech , for some reason perhaps thinking to keep dirt out, plugged up the primer hose nipple on the carburetor body with RTV. Since the carburetor relied on the primer to be vented for a bowl vent (primer would not work if bowl had any other vent) then of course, air pressure in the carburetor float chamber would prevent the fuel from rising enough to close the float - and due to the constant flow of fuel, fuel would have run through the main jet and idle metering passages. sort of a reverse vapor lock.

[KE4AVB]

What, No JB weld. Seems to be a favorite fix around here.

DIYer do crazy things at times trying to fix something that is not broken, to try to keep from spending a penny, or spend a lot trying to fix a problem that they don't understand.

One time I got in an engine where the attempted fix was to RTV the blown head gasket. What a mess to clean up.

[creia]

That was fun and we can all learn from this. Let's do some more of these diagnostic challenges!
Michael

[38racing]

I think it's tecumseh that has carbs with a tiny bowl vent hole up on outside that can get easily plugged.

[bgsengine]

I think it's tecumseh that has carbs with a tiny bowl vent hole up on outside that can get easily plugged.

yeah but not since EPA laws kicked in - newer carbs come with internal bowl vents (or the primer doubles as vent) - there can be no external venting of any gas fumes (within some strict limits) from fuel systems, since 2012 or so - which is why newer models have EPA approved non-permeable fuel lines, and charcoal canisters and EVAP systems, etc.