goldwing2000
New User
Background:
1972-ish IH 3400A loader tractor with backhoe
C-175 IH engine with MS TSX-985SL carb
Was purchased with engine "running on two cylinders", according to previous owner. They replaced the cylinder head and did some carb work.
What I've done so far:
Pulled engine oil drain plug and about three gallons of gas/oil mix came out. Checked fuel pump, not leaking internally, replaced anyway.
Power-washed tractor for over 3 hours to blast away decades of gunk.
Replaced spark plugs, wires, cap, rotor, points and condenser. Reconditioned distributor (disassembled, cleaned, checked for excessive wear).
Performed compression test. Pressures are a little low, but all within spec and balanced (expected from a 40+ year old engine).
Pulled oil pan, inspected oil pump and bearings for damage.
Pulled carburetor, disassembled, hot-tanked, inspected and re-assembled with new bowl gasket. Found that gasket for fuel nozzle was missing, attempted to seal temporarily with RTV.
The issue:
Engine starts up but after just a couple minutes, the intake manifold gets ice cold, exhaust is pushing black smoke, engine bogs excessively and RPMs barely respond to throttle. Unspecified liquid is seeping from exhaust pipe at manifold. At first I thought the fuel pump was pushing fuel past the float valve and it was flooding, so I installed a 1-4psi pressure regulator. No help. Next, I put a sight tube on the bowl to check float level while running. This is where things get interesting. The fuel level in the float bowl is essentially zero. The engine is sucking up the fuel as fast as the fuel pump can push it in. If I pull the power on the shutoff solenoid (which blocks off the main fuel nozzle), the RPMs pick up immediately, the float bowl fills and it runs great for about three seconds until the fuel is depleted.
My thoughts:
A severely oversized main jet may be allowing the nozzle to simply be a straw and suck up all the fuel.
A crack or hole somewhere that's allowing ALL the fuel to be drawn into the manifold.
Engine is somehow making too much vacuum? Haven't put a vacuum gauge on it yet.
Engine is pushing all that raw, unburned fuel into the exhaust and muffler, which is then draining back into the crankcase and diluting the oil.
Planning to disassemble the carb again this weekend and perform another close inspection, paying particular attention to the main jet, nozzle and corresponding areas.
My options at this point:
Try to throw a premium rebuild kit at it for $65
Replace it with a 14996B Zenith from this site for $240.
Anybody experience this particular issue??
1972-ish IH 3400A loader tractor with backhoe
C-175 IH engine with MS TSX-985SL carb
Was purchased with engine "running on two cylinders", according to previous owner. They replaced the cylinder head and did some carb work.
What I've done so far:
Pulled engine oil drain plug and about three gallons of gas/oil mix came out. Checked fuel pump, not leaking internally, replaced anyway.
Power-washed tractor for over 3 hours to blast away decades of gunk.
Replaced spark plugs, wires, cap, rotor, points and condenser. Reconditioned distributor (disassembled, cleaned, checked for excessive wear).
Performed compression test. Pressures are a little low, but all within spec and balanced (expected from a 40+ year old engine).
Pulled oil pan, inspected oil pump and bearings for damage.
Pulled carburetor, disassembled, hot-tanked, inspected and re-assembled with new bowl gasket. Found that gasket for fuel nozzle was missing, attempted to seal temporarily with RTV.
The issue:
Engine starts up but after just a couple minutes, the intake manifold gets ice cold, exhaust is pushing black smoke, engine bogs excessively and RPMs barely respond to throttle. Unspecified liquid is seeping from exhaust pipe at manifold. At first I thought the fuel pump was pushing fuel past the float valve and it was flooding, so I installed a 1-4psi pressure regulator. No help. Next, I put a sight tube on the bowl to check float level while running. This is where things get interesting. The fuel level in the float bowl is essentially zero. The engine is sucking up the fuel as fast as the fuel pump can push it in. If I pull the power on the shutoff solenoid (which blocks off the main fuel nozzle), the RPMs pick up immediately, the float bowl fills and it runs great for about three seconds until the fuel is depleted.
My thoughts:
A severely oversized main jet may be allowing the nozzle to simply be a straw and suck up all the fuel.
A crack or hole somewhere that's allowing ALL the fuel to be drawn into the manifold.
Engine is somehow making too much vacuum? Haven't put a vacuum gauge on it yet.
Engine is pushing all that raw, unburned fuel into the exhaust and muffler, which is then draining back into the crankcase and diluting the oil.
Planning to disassemble the carb again this weekend and perform another close inspection, paying particular attention to the main jet, nozzle and corresponding areas.
My options at this point:
Try to throw a premium rebuild kit at it for $65
Replace it with a 14996B Zenith from this site for $240.
Anybody experience this particular issue??
