Dear Ole Mechanic;

Help!  My chainsaw won’t start!  It is a four or five-year old Poulan® saw with a sixteen-inch bar.  I have put in a new sparkplug, dumped out the old gas, and put in a fresh gas-oil mix.  I can push on the primer bulb, pull on the starter cord untill I'm blue in the face, and not even get a pop or a sputter.  Any suggestions?Chainsaw

Blue Face


Dear Blue;

Oh boy--one of those temperamental two-stroke engines.  OK--back to basics.  An gas engine will not run without spark, fuel, and compression.  There are other factors involved, but if one of the above three items is missing, I will guarantee that the engine will not run.  Since you have put in a new sparkplug, I will start there.  Take the plug back out, reconnect it to the sparkplug wire, and ground the sparkplug by making sure that the outside metal of the plug is touching a metal part of the engine.  That may be a little hard to do with all of the plastic used today, and you may even need to make a jumper wire to ground the plug.  With the sparkplug grounded, pull on the starter cord rapidly while watching the sparkplug gap.  You should see a nice, hot, blue spark or even several sparks as the engine spins.  If you get a weak, yellow spark or no spark at all, then it is time to do some major disassembly of at least some of the plastic, as you are going to need to test the ignition or kill switch.  Now, don’t have a cow because you don’t know how to test the switch--the test is not hard.  All you need to do, once you find the back of the switch, is disconnect the small wire from the switch and make sure that it is not grounded.  Now, pull the starter cord again and check for spark at the sparkplug.  If you now have spark, then you have found your problem--a bad switch.  If there is no spark, then it is time to go deeper to expose the magnets in the flywheel and the ignition coil.  There is not an easy test for the coil other than looking for grounded or loose wires.  If you find either, then it is time for a new coil or a new saw, whichever is cheaper.  The magnets are a different story.  If there is rust on the face of the magnets where they go past the coil, then they need to be sanded until you can see the metal of the magnets again.  With the magnets clean, test for spark at the sparkplug again.  If there is still no spark, then refer to the “. . . new coil or new saw” advice above.

If you had spark during the first test, then the next test is for compression, as you already have the sparkplug out.  With the sparkplug and wire out of the way, put your thumb tight over the plug hole and pull the starter cord again.  The compression is good enough if you cannot keep the air from getting out around your thumb as the engine turns over.  If you can keep the air from escaping or there is very little pressure on your thumb, then refer to the “. . .new coil or new saw” advice, and just forget about the new coil.  Parts and labor to overhaul a saw will cost more than a new saw.

With both spark and compression present, then it is time to check the fuel system.  First, look at the primer bulb very carefully.  There are two types: one has a hole in the center of it and should have nothing but air in it., the other does not have a hole in it and after pushing it several times should have fuel in it.  The most common type for chain saws--including your Poulan®--is the one without a hole.  That is the one I will discuss.  If there are cracks in the bulb, which seems to be a very common problem with today’s gasoline, then it will need to be replaced.  They are available at most stores that sell chainsaws and cost a buck or two.  Just keep things clean as you replace, it because there are very tiny holes in the carburetor where the gas in the bulb will wind up.  It seems that the holes will plug up if you so much as look at them cross-eyed.  If the primer bulb is working but has more foam in it than gas, then it is sucking air somewhere.  Since air is easier to move than gas, the engine will get air instead of gas.  The air could be coming from an empty gas tank; however, since you put in a fresh mix, it is probably coming from a cracked fuel line.  This is also a common problem with today’s gas.  Yes, the fuel line is available, but it is a little harder to find than the primer bulb.  Be sure to take a piece of the old fuel line with you, as there are several different sizes.

If everything checks out OK, then it is time to remove and disassemble the carburetor.  Be careful and be clean, because although there are not many parts or passageways, they are small.  There are only about five or seven screws, depending on the model of saw that you have, to get to the passageways that need cleaning.  Do not use a compressed air blow gun to clean the passageways, as that thing that looks like a plug is actually a very fine screen that will blow out easily and will never be found again.  No, they are not available unless you buy a new carburetor or a new saw, whichever is cheaper.  If you are careful with the gaskets, you will probably be able to reuse them.  There is only one problem left.  After cleaning the carburetor, you will need to readjust the mixture screws, as they should have been removed during the cleaning.  The problem is that it takes a very special tool to be able to adjust the screws.  Poulan® does not make that tool available to anyone except licensed Poulan® service centers.  Refer to the “. .  new coil or new saw” advice and just forget about the new coil, and may I suggest a brand other than Poulan®.

Herr Professor Nuzanbolts