I have a Stihl MS230C in for repair of what should have been a simple job. It hadn't been run for two years. I disassembled the carb, cleaned it in our sonic cleaner, ordered and installed all new gaskets, and reassembled it. Now when I prime it to start, I get no gas flowing into the carb. I pulled the gas line and gas spewed all over me. Apparently, the primer worked in pulling gas up to the carb. It just stops there. I disassembled it again to check if I perhaps assembled it incorrectly. I did assemble it correctly. I checked for flow through the intake and it's clear. When I assembled and installed it again I have the same issue. Any ideas what could be constricting the flow after assembly? Thanks
#2
Hammermechanicman
Going to assume you assembled the fuel pump properly. Is the impulse line hooked up and is it in good shape. Non working impulse can cause metering diaphragm not to move so no fuel past needle. Do you get fuel i to the fuel pump section of the carb?
Tank dirty?
Fuel filter in the tank clogged?
Fuel lines cracked or loose?
Diaphragm gaskets installed proper and new?
Fuel lines are probably cracked and dry from the two year vacation. I know I use Stabil fuel stabilizer and leave it full of gas and oil over the winter. Seems to save me from replacing lines and tanks. Drain them for the winter and I have to start replacing lines. Guess they dry our and crack with no fuel and oil in them in the cold garage. My trimmer fuel tank replacement was $86.00 alone.
Is it a Harbor Freight sonic cleaner? Heard from someone here that had one, those are not that great in cleaning. He has another industrial type now $$$$. Your carb might still be plugged up??.
Put your ear close to the carb while priming and listen for a sucking air sound. I am betting that you have a check valve stuck open and it won't prime and may require complete carb replacement.
#6
StarTech
The HFT USC cleaner is only a 60W cleaner much like my first unit by Kendall and yes it will take several cycles in it to things clean. Even my 160 w USC takes a couple 30 minutes cycles sometimes but of course it got a 10 liter tank too.
Not familiar the MS230 carburetor; although, I have service a couple over the last 11 yrs. But said check valve(s) on the metering side can be stuck open and if so then it is a new carburetor time.
Thanks for all the replies. Our sonic cleaner is a GT Sonic Professional cleaner. My first thought was operator error, so I double checked my assembly. The tank is clean, the gas replaced and the filter is good. One thing I didn't mention is the primer bulb never fills with fuel. Could the metering valve be stuck closed? Would that explain fuel being drawn up to but not into the carb?
#8
Fish
The primer bulb is actually a purge, it pulls fuel through the carb, and then sends it back to the tank. Check and see if you have the lines hooked up backwards.
#9
Hammermechanicman
The ms250 has a complicated primer system. It is not an air purge, it pushes fuel into the carb. The carb only has one fitting.
On this particular carb it's not possible to hook them up backwards. The supply line can't stretch to the purge line and vice versa. The diagram above isn't the same carb setup. I'll see if I can find the one I have.
#11
dougand3
The first time I saw that MS250 IPL, I asked WTH???? Stihl has figured out a way to replace a line between the carb and pickup with 6 lines, T's and maybe disgronifacators.
On this particular carb it's not possible to hook them up backwards. The supply line can't stretch to the purge line and vice versa. The diagram above isn't the same carb setup. I'll see if I can find the one I have.
Does the carb have 1 or 2 nipples to attach a hose to? The 230/250 usually has one but people sometimes ditch the goofy plumbing and install a carb that can use a purge bulb.
Push home the fuel pump (short
intake stub facing the air filter)
until retaining tabs snap into
position.
– Connect suction hose from
carburetor to the short stub on
right.
– Connect hose from connector to
long stub on left.
The hoses must not be
interchanged.
So the primer does suck fuel through the carburetor.
Now one possible is a stuck main nozzle check valve (in open position). Unless it can close all the primer would do is suck air in through the main nozzle as it would the path of least resistance.
#14
Fish
Can you flip the primer bulb over, it may be backwards.
So the primer does suck fuel through the carburetor.
Now one possible is a stuck main nozzle check valve (in open position). Unless it can close all the primer would do is suck air in through the main nozzle as it would the path of least resistance.
The Primer does suck fuel up TO the carb, but not through it. I just went over the primer hoses for the third time to be absolutely sure there's no air leak. I have the carb off and when I push the primer bulb, I get a strong flow of fuel coming up from the tank. I gotta believe at this point that something inside the carb is blocked so badly that the sonic cleaner isn't getting to it.
#16
Hammermechanicman
For fuel to flow through the carb the diaphragm needs to be depressed so the metering needle opens. Is the impulse line connected to the barb on the cylinder to the handle assy? If you remove the carb and put a drop of oil in the small hole of the intake boot and pull the rope you should see the oil suck in and then blow out with crankcase pressure. If that is good you can pressureize (max 7 psi) the fuel inlet barb on the carb with the carb bolted in place and holding throttle wide open and pull the rope vigorously. With each revolution of the crank you should see a slight drop in pressure when the metering needle opens. Also, pinch off the line to the tank vent and see if that makes a difference.
#17
Hammermechanicman
Just so you know. The primer bulb does not fill with fuel. It pumps air into the line for the tank vent to pressurize the fuel tank to push fuel into the carb. If you pull the line off the carb and pump the bulb it should spray fuel out the line to the carb. Stupid attemp at an easy start design.
#18
Fish
Reassemble in the reverse
sequence.
VA 135RA221
– Push home the fuel pump (short
intake stub facing the air filter)
until retaining tabs snap into
position.
– Connect suction hose from
carburetor to the short stub on
right.
– Connect hose from connector to long stub on left.
The hoses must not be
interchanged.
#19
Fish
I haven't watched this yet.
#20
Hammermechanicman
To the OP. This is a 251C. Does the carb you have look similar to this with 2 barbs on the carb or does it have a single barb?
