Small Engine Repair: Checking Fuel Pump Diaphragm & Inlet Needle on a Diaphragm Carburetor
**Always follow the instructions in your repair manual when doing repair or maintenance work on Outdoor Power Equipment. Manuals can be found at the manufacturers website.**
In this video I show how to check the fuel pump diaphragm and inlet needle for leaks on a diaphragm carburetor. A diaphragm carburetor is used on hand held power equipment, and are popular because they will work in any position. All chainsaws, trimmers and blowers that I have seen use a diaphragm carburetor. To check the fuel pump and inlet needle, pressurize the carburetor to 10 psi through the fuel inlet. The carburetor should hold the pressure fairly steady, and if it doesn't than there is a leak around the fuel pump diaphragm or inlet needle. You can pin point the leak by dunking the carburetor in water while it is pressurized. If the leak is around the fuel pump diaphragm, than either the fuel pump diaphragm, fuel pump diaphragm cover or the body of the carburetor is at fault. If the leak is coming out of the venturi, than the inlet needle or seat is faulty.
Tools used:
- 3/8" wrench to remove carburetor
- Mityvac to pressurize the carburetor
- Needle Nose plyers
Specifications:
- Carburetor should be pressurized to 10psi through the fuel inlet. Never exceed 10psi. Its important to run fuel through the carburetor before testing. A wet carburetor will hold the pressure better than a dry one.
HOW TO - Two Cycle Carburetor Cleaning / Rebuild (Part 1 of 2)
Since this is only an instructional video series I was not going to use any carburetor cleaner. Basically i'm explaining how to check the pump diaphragm, & metering diaphragm as well as how to clean a two cycle carburetor.
K10-WAT & K20-WAT rebuild kits are for all WA & WT series Walbro carburetors. Most of the time you can get away with ordering a K10-WAT if you only need to replace the diaphragms. If you need to do a complete rebuild order K20-WAT.
There are special tools for checking both Zama, and Walbro carburetor metering levers but I have found that a metal straight edge ruler is just as accurate.
WALBRO METERING LEVER TOOL :
http://compare.ebay.com/like/110600202910?var=lv<yp=AllFixedPriceItemTypes&var=sbar&rvr_id=216029650572&crlp=1_263602_309572&UA=WVF%3F&GUID=9170fef012e0a0645631a321ffbb97bc&itemid=110600202910&ff4=263602_309572
ZAMA METERING LEVER TOOL :
http://cgi.ebay.com/NEW-ZT-1-Zama-Z-Carburetor-Metering-Lever-Tool-/110600190012
This rebuild / cleaning procedure will also apply to carburetors without a purge bulb. I will do a proper video when I have an actual rebuild or cleaning.
How to test motorcycle CDI box, ignition coil
Mostly concerning CDI boxes and ignition coils... for more technical information feel free to message me, I'll send you some good info
How a carburetor works, schemes and explanations
This video explains, not in too much detail, how a 28mm Walbro diaphragm carburetor works (using mainly schemes to point out what happens inside). It explains what occurs at the venturi, what the butterfly valve is for, how the needle doses the amount of fuel, and how does the diaphragm slide adjust itself.
How to diagnose carburetor vacuum leaks on your motorcycle
This is a simple video demonstrating the best method to detect vacuum leaks around your carb boots. Vacuum leaks are a fairly common problem in older bikes, and luckily they can usually be remedied quickly and easily, the first step however is diagnosis.
If your bike is running rough, won't rev up or has an irregular idle, before you take off the carbs and open them up, check for vacuum leaks. A vacuum leak occurs when too much air is introduced into the combustion chamber via a failure in one or more of the carburetor boots or other rubber mating surface. When too much air is sucked in, then the bike cannot combust the gasoline efficiently; there must be an optimal ratio. Therefore it is up to you to detect these leaks, and either plug them up or replace the carb boots.
In this particular bike, the engine was running VERY lean. Not only did we have vacuum leaks, but the baffles were taken out of the engine, and the previous owner had removed the air filter and neglected to install a new one. This is not only dangerous by allowing foreign material to enter the engine, but it also makes the engine run much hotter, as lean explosions create more heat than regular ones (think about blowing on a fire in your fire place: more air, hotter fire). This can be detrimental to a variety of parts in the engine, and it is a good thing we didn't ride this bike around too much before finding the problem.
If anyone has any questions as to why this is important or how to find/repair these leaks, leave a comment and I will respond.
Thank you
Small Engine Repair: Cleaning Carbon Buildup on the Exhaust Port & Muffler on a 2 Stroke Engine
**Always follow the instructions in your repair manual when doing repair or maintenance work on Outdoor Power Equipment. Manuals can be found at the manufacturers website.**
Small engines used in outdoor power equipment often suffer from carbon build up in the cylinder head, Exhaust port and muffler. The is more common in 2 stroke engines than 4, but it does occur in both. In this video I inspect the Exhaust port and muffler on a Echo SRM-230 trimmer. The muffler was very clean, but the Exhaust port had carbon build up that blocked half the port. To clean the port, rotate the engine until the piston skirt is covering the Exhaust port, and take a screw driver and lightly scrape the port to remove the carbon. Than take compressed air and blow out the port to remove the carbon pieces. Mufflers on small engines are usually sealed units, so cleaning them is very difficult if not impossible. Its easy and less expensive to replace a sealed muffler with a new one. Some mufflers have screens, which can be cleaned with a wire brush and compressed air.
This trimmer was run by the previous owner without a trimmer line knife attached to the deflector. This allows the trimmer line to extend beyond the manufacturers recommended length, and this causes a excessive load on the engine. I believe this is primary responsible for the carbon build up on the port.
Small Engine Repair: Checking a Vacuum Fuel Pump / Fuel System on a Kohler V-Twin Engine
**Always follow the instructions in your repair manual when doing repair or maintenance work on Outdoor Power Equipment. Manuals can be found at the manufacturers website.*
Checking the fuel system, and vacuum fuel pump on a V-twin 25HP Kohler engine involves checking the fuel lines that attach to the pump, and checking fuel flow. The first step is to check to make sure fuel can flow from the gas tank to the fuel pump. To do this, disconnect the fuel line from the vacuum inlet fitting on the vacuum pump. Take the fuel line and lower it to a point that is below the fuel tank and see if gravity will cause fuel to flow from the tank through the line. If fuel flows, than the line is clear. If fuel will not flow, than check the fuel filter to see if it is restricted. Also check the fuel tank shut off valve if the tank is equipped with one. The valve may be in the off position, or dirty and restricted. Check the fuel tank cap to see if the vent on the fuel tank cap is plugged. If the fuel tank cap vent is plugged than fuel will not flow out of the fuel tank.
Next, check the pulse line on the vacuum pump. Make sure it is connected correctly to both the vacuum pump and the engine crankcase. Also, make sure the engine is not overfilled with oil and the pulse line is not filled with oil. If the engine oil is overfilled with oil, than oil can make its way into the pulse line and block the pressure necessary to operate the fuel pump.
The next thing to check is the fuel line from the vacuum pump to the carburetor. To do this, take the line off and make sure the line is in good condition, and there are no restrictions in the line.
The final check is to make sure the vacuum pump is pumping fuel. Disconnect the vacuum pump outlet line where it connects to the carburetor inlet, and turn the engine over. If fuel flows from the vacuum fuel pump, than the pump is working. Kohler does not provide a more precise way of checking the vacuum fuel pump, and they say if you get fuel flowing through the pump when the engine is turned over, than the fuel pump is working correctly. Kohler does say the vacuum fuel pump should pump a minimum of 2 gallons of fuel per hour with a pressure at 0.3 psi and a fuel lift of 24 in, but they do not give you a method to check these specifications.
NAPA Service Tools Cylinder Leak Down Tester
Designed To Measure The Ability Of An Engine Cylinder To Hold Compressed Air Using Shop Air Pressure & Supplements Compression Tester, Pinpoint Bad Valves, Worn Rings, Cracked Cylinder Walls, Blown Head Gasket; Furnished w/ Rubber Boots To Protect Gauges, Includes Precision Regulator w/ Combination Adapters, 26" Hose Assembly, 2 1/4" Special Gauge Has Multi-Colored Band For Measuring Low, Moderate & High Leakage; Scale Range Up To 100%, Second Gauge Has Dual Scale w/ Ranges Up To 100 psi & Up To 7 Bar, Allows Technician To Monitor Input Airline Pressure NAPA part number: SER CLT-2
Small Engine Repair: How to Check a Solenoid Fuel Shut Off Valve on a Kohler V-twin Engine
**Always follow the instructions in your repair manual when doing repair or maintenance work on Outdoor Power Equipment. Manuals can be found at the manufacturers website.**
Solenoid fuel shut off valves are used to close the main jet or main fuel circuit in the carburetor when the key is turned off. The solenoid valve works by using a spring loaded plunger to press against the main fuel circuit passage and prevent fuel from entering the passage. When the key is turned on a magnetic field is generated in the solenoid and the plunger is pulled into the body of the solenoid, thus opening the main fuel circuit. By closing the main fuel circuit when the key is turned off, the fuel in the carburetor is prevented from entering the engine, and this prevents unburned fuel from entering the engine while it is shutting down, and this helps prevent engine back fires.
When the engine is stored with fuel in the carburetor for long periods, there is a risk of the old fuel causing contamination and corrosion to develop on the solenoid plunger causing it to freeze and no long move freely. When this happens the plunger is stuck in the fully extended position, and this closes off the main fuel circuit not allowing fuel to enter the engine when the key is turned on, and this prevents the engine from starting.
