QuestionThis Ryobi was working for more than 10 yrs, until this week it was difficult to start. The fuel lines were disintegrating, so I replace them with new ones. Fuel filter (in the tank) still the same, it is clean. It simply doesn't start. I disassembled everything, open the carburator, try to find some dirt or blocked small hole, nothing, as far as I was able to see, it was clean. The muffler is dirt, black with burnt oil. I saw another post, will try to clean it up. The trimmer also doesn't start with the muffler removed (it doesn't need it installed to test run, right?) After primming fuel 4 to 5 times, sometimes the engine starts slowly when fully chocked. Sometimes it stays running in low rpm for a minute, then dies. When running fully chocked, if I move the chocker plate to open a little bit of more air (even a little little bit), engine accelerates for few seconds and then dies. It never starts at half chocked or fully open, only fully chocked. The little I understand, if the engine dies when giving it more air, it seems the mixture goes too poor, or fuel is missing. When runing fully chocked, I can see small drops of fuel pulling out of the chock small hole. Spark plug is clean and gap adjusted, checked the continuity of the on/off switch, when in off position it short circuit that particular connector of the high voltage coil to ground, when in On position that connector is isolated from ground, even that I can measure some continuity from that connector to ground always, I guess it is the inductor wire inside the coil that one side is connected to ground. Except for the muffler, the engine is very clean and well maintained. This unit was used no more than 15 minutes each other week during 10 years, small backyard.
What is killing me; why the engine runs fully chocked? It should not since the mixture is super rich. Perhaps air is leaking into the carburator/intake valve through bad gaskets? perhaps the fuel filter is not allowing enough fuel?
Questions:
It should not run fully chocked, right?
It can test run without the muffler?
It can test run only the engine, with the arm and attachment removed, right?
There are two plastic type of screws with springs on top of the carburator, supported by another black pastic body, I didn't touch that, what is it?
Thank you for any help. I really don't want to trash this nice and clean unit. It seems something simple, but I can't figure out.
Ah, the primer bubble doesn't return fast after 3 or 4 presses, it stays flattened for almost 10 seconds, as if fuel is getting difficult to come out of the carbutator, or, to enter the carburator.
Removing fuel from the tank, or turning the engine upside-down, when no fuel goes to the carburator, then the primming bubble works fast, with only air...
Any help will be very much appreciated.
Thank you,
Wagner.
AnswerWagner
Questions:
It should not run fully choked, right?
They can run fully choked because the carb is starving for fuel and by choking the carb you are forcing fuel to run.
It can test run without the muffler?
Sometimes it can the problem is that you need the muffler for back pressure to the engine and the mixture of fuel and air
It can test run only the engine, with the arm and attachment removed, right?
Yes you can it will run with no load.
There are two plastic type of screws with springs on top of the carburetor, supported by another black plastic body, I didn't touch that, what is it?
They are adjustment screws 1 is for idle the other is for high speed.
Your primer is bad the small primer pump wont let fuel return so it will stay flat.
You really need a new carb If you are good with engines you can rebuild the carb,But that is not a guarantee that the carb would be fixed.
Here is how the carburetor works:
The membrane of the Fuel Pump is activated by the vacuum pulses from the crankcase.(Muffler) The fuel is pumped and enters through the Fuel Inlet. As it passes the Check Valve and a filter, the fuel is directed to the Needle Valve which is opened by the atmospheric pressure acting on the Metering Diaphragm. The pop-off pressure is set by the spring (Metering Lever Spring)
At Low RPM the fuel mainly enters the Venturi through three Idle Holes which are situated one after the other. This ensures a smoother acceleration and prevents the mixture of running too lean when the Throttle Valve is being opened.
The amount of fuel is regulated by two screws: HI and LO (for high and low
RPM)
Here is some help for this problem
Carburetor related problems trouble shooting guide
low power at wide open throttle
Causes
Idle mixture screw not properly adjusted
High speed mixture screw not properly adjusted
Throttle adjust screw adjustment
Fuel pump diaphragm (leaking/stiff)
Strainer (restricted/plugged)
Metering lever, spring (worn/binding)
Metering lever set to low
You need to look at the carburetor to see the model #
I belive this is a ZAMA Carb. I can get you a rebuild kit or a replacement carb.
