this thread concerns a sears craftsman edger model 536-772100 engine #143-993502, carb #640156'the problem is the edger will run for 3-5 minutes then stop. i have done the following: cleaned carb, changed air filter, changed spark plug, cleaned gas tank, used fresh fuel. alas, all to no avail. can you help? thanks.
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craftsman won't run
- Thread starter pete g
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Export threadLawnranger
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The first thought that comes to mind is that the vent in the fuel tank cap may be plugged or restricted which causes a vacuum to build in the tank. To find out if that is the case, make the problem occur and loosen the cap just enough to let some air in and try starting & running the engine again. If the problem goes away with the cap loose, you will need to clean the vent or replace the cap. I'm starting with the simplest check first so let us know what happens after you try loosening the cap.
Lawnranger
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Yes, usually there is a vent in the cap to allow a small amount of air in to displace the fuel so the tank will not build a vacuum. Sometimes you cannot see the vent on some caps so that is why you simply loosen the cap to diagnose the problem.
Now that the engine will not start I will say the following:
An engine needs three factors present and in the correct proportion to start and run properly - the correct air/fuel ratio (fresh, quality fuel is a must), sufficient compression (arguably 90 P.S.I. or better) and sufficient spark at the correct time. If one of these factors is missing or out of proportion, the engine will run poorly or not start/run at all. Your task is to find the missing factor by inspecting and testing the systems involved. Which factor is missing or out of proportion in your case?
If you do not know how to check for spark or perform the necessary checks and tests, youtube has some videos that will guide you through the process. Simply search youtube for what you want to test or check.
There are conditions that will prevent an engine from starting even though all three factors are correct such as a plugged muffler/exhaust, old/contaminated fuel and I am sure there are more possibilities but I will not try to list them all here so I am going on the assumption that one of the factors is missing and that all other components are functioning properly.
You will need a compression gauge to test compression so if you do not have one or do not have access to one you will need to take it to someone who can test it for you. You will also need a spark checker which can be made from an old, working spark plug by clipping off the side electrode, connecting the plug to the lead and resting the metal hex of the spark plug on the metal part of the engine but this is not always as easy as it seems as many engines have plastic shrouds and other obstacles in the way. My method of testing for lack of fuel is to spray a shot of carburetor cleaner directly into the carburetor (air filter removed) and try to start the engine. If the engine starts and runs for a second or two and then dies you most likely have a fuel delivery problem.
Perform the necessary tests, report back with your findings and you will receive further advice based on your answers.
Now that the engine will not start I will say the following:
An engine needs three factors present and in the correct proportion to start and run properly - the correct air/fuel ratio (fresh, quality fuel is a must), sufficient compression (arguably 90 P.S.I. or better) and sufficient spark at the correct time. If one of these factors is missing or out of proportion, the engine will run poorly or not start/run at all. Your task is to find the missing factor by inspecting and testing the systems involved. Which factor is missing or out of proportion in your case?
If you do not know how to check for spark or perform the necessary checks and tests, youtube has some videos that will guide you through the process. Simply search youtube for what you want to test or check.
There are conditions that will prevent an engine from starting even though all three factors are correct such as a plugged muffler/exhaust, old/contaminated fuel and I am sure there are more possibilities but I will not try to list them all here so I am going on the assumption that one of the factors is missing and that all other components are functioning properly.
You will need a compression gauge to test compression so if you do not have one or do not have access to one you will need to take it to someone who can test it for you. You will also need a spark checker which can be made from an old, working spark plug by clipping off the side electrode, connecting the plug to the lead and resting the metal hex of the spark plug on the metal part of the engine but this is not always as easy as it seems as many engines have plastic shrouds and other obstacles in the way. My method of testing for lack of fuel is to spray a shot of carburetor cleaner directly into the carburetor (air filter removed) and try to start the engine. If the engine starts and runs for a second or two and then dies you most likely have a fuel delivery problem.
Perform the necessary tests, report back with your findings and you will receive further advice based on your answers.
Lawnranger
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thanks lawnranger for your advise i would like to sub the carburetor. my question is do i have to use the exact same carb for the test?
Not quite following what you mean by use the same exact carb for the test. To test if it is a fuel problem, just spray a shot of carburetor cleaner in the original carb throat and try to start the engine.
Lawnranger
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Job well done.