QuestionQUESTION: The unit will not start when cold (temp below 35 or so), unless I prime with carb cleaner down throat of carb, (I have to leave the bottom cover of Toro unit off). I've cleaned the carb & checked the spark plug gap (.030). The unit runs fine after warmed up & will restart if done within 10 minutes. I've choked, pushed the prime button numerous times, and it will not start when cold - unless I spray carb cleaner down throat of carb. When it starts, I must leave the choke on for about 20-30 seconds and gradually step it off. Then it runs fine. Any suggestions?
ANSWER: Hello Kevin:
>>What is the Engines Compression?
>>Did you Soak the Carburetor Overnight in Carburetor Cleaner?
>>Low Compression will cause this Problem and Usually the Low Compression is caused by a Restricted Muffler/Spark Arrestor Screen or Exhaust Port, a Damaged Cylinder/Jug, a Blown Cylinder/Jug Seal or a Leaking Crankshaft Seal.
>>The Following is a Basic Instruction File for Doing a Diagnostic on the Engine for this Problem. Any Input is Appreciated.
>>**Remove the Muffler and Make Sure the Exhaust Port is Clear.
>>If it is, then Try to Start the engine with the Muffler Off.
>>If it Starts and Runs Properly, then Clean the Spark Arrestor Screen in the Muffler or Replace the Muffler if Required.
>>With the Muffler Off, Inspect the Cylinder/Jug and the Piston for Damage.
>>If the Cylinder/Jug and Piston Look Smooth like Glass, then they are OK.
>>If they Look like Sandpaper has Scratched them or there are Gouges in Either the Piston or Cylinder/Jug, then the Engine is Trashed.
>>The Following is a Basic File I Made for Cleaning Carburetors. Any Input is Appreciated. Even though the Carburetor Looks Clean, the Internal Passages May be Restricted with Varnish that Gas Causes to Build Up over Time.
>>Spray Cleaners Remove this Varnish in Layers, so Soaking is the Only Sure Way to Remove ALL this Varnish.
>>I have Found that Most People can Use a Breakdown/IPL and Disassemble the Carburetor Enough for Proper Cleaning.
>>You Only have to Remove the Bowl (if Applicable), Float Pin (if Applicable), Float (if Applicable), Needle Valve.
Remove Any Adjustment Screws that Go Into the Carburetor Body. The Welsh Plugs Do Not have to be Removed.
>>If you are Able to Remove and Disassemble the Carburetor and Keep the Gaskets Intact, then Usually these Gaskets can be Reused. The Only Parts you May Need to Replace is the Needle Valve.
>>The Float Needle Usually is Not Replaced Unless it is Not Operating Properly (the gas flow not shutting off and the carburetor is Flooding). Do Not Remove the Main Nozzle. This is a Pressed Fit and Removal is Not Required for Cleaning. Soaking and Blowing the Carburetor Out After Soaking will Clean the Nozzle.
>>Once Disassembled, then Soak the Carburetor Body and Parts in a 1 Gallon Can of Gunk Carburetor Cleaner Overnight. The Can has a Parts Tray Inside it for the Small Parts.
>>Once the Carburetor and Parts are in the Cleaner, you can Replace the Lid for Safety and to Prevent Accidental Spillage. Then Blow Out the Passages with Compressed Air.
>>Note: **Pay Close Attention to the Adjusting Screws and Remember which Hole the were Removed from. They MUST be Replaced Into the SAME Hole they were Removed from!!!**
>>***(Do Not Use High Pressure Air for the Zama Carburetors, they have Check Valves for the Primer and these are Usually Blown Out of the Carburetor if Not Careful. Allow the Zama Carburetor to Set on a Drip Pan and Dry)***.
>>****All the Carburetor Adjustments are the Same for Lawn Mower and Trimmers. There are Several Location for the Air Mixture Screws. The Idle Air Mixture Screws are Usually Located at the Top of the Carburetor Bowl and the Top of the Carburetor Body.****
>>If the Main Air and Idle Air Mixture Screws are Side by Side on the Side of the Carburetor, then the Idle Air is Nearest the Engine. The Main Jet Air Mixture Screw is Located in the Bottom of the Carburetor Bowl or Beside the Idle Air Screw on the Side of the Carburetor Body.
>>Some of the Older Model Carburetors have the Main Jet Mixture Screw Straight in from the Top of the Carburetor Body (this is Rare anymore). If you have Cleaned the Carburetor (Disassembled and Soaked Overnight in Carburetor Cleaner (I Use Gunk). Then Blow Out the Passages with Compressed Air and Install a New Kit if Required. Now Setting the Air Mixture Screws:
>>****Turn the Idle Air and Main Air Mixture Screws In Until SNUG **Do Not Jam** Then Reverse Both Screws 1 1/2 Turns. Holding the Throttle Full Open, Start the Engine. Set the Idle Screw so the Engine will Idle (even if a little high) and then Using the Governor Arm (on chainsaws and trimmers use the Trigger) Rev the Engine Up and Down Until and Turn the Main Air Mixture Screw Clockwise Until Proper Revs are Obtained. Occasionally you May have to Turn Counter Clockwise to Achieve the Proper Revs. Now Allow the Engine to Idle. Set the Engine Idle Screw (Not Idle Air) so the Engine will Stay Running if Required. Now Set the Idle Air Mixture Screw so there is No Hesitation when Throttling from Idle to Full Throttle. Reset the Engine Idle if Required.****
>>If This Carburetor has a Single Air Adjustment (Except Tank Mounted 9200 and 100900 Engine Model Carburetors), Use the Section Above that Pertains to Full Throttle RPM Air Mixture Screw and then Adjust the Screw if Required to Eliminate Any Hesitation when Throttling from Idle to Full Throttle.
>>For the 9200 Model Tank Mounted Carburetor Adjust the Air Mixture Screw Full In, then Reverse 1 1/2 Turns. Set the Throttle Lever to Full Throttle and Start the Engine.
>>Now Carefully Use 1 Finger and Open the Throttle Plate and Over Rev the Engine Slightly. If the Engine Over Revs and Does Not Struggle to Over Rev, then the Carburetor is Set. If the Engine Struggles to Over Rev, then Turn the Adjustment Screw In 1/4 Turn and Repeat the Over Rev Test.
>>If you Adjust to 1/2 Turns In and the Engine Still Struggles to Over Rev, then Return the Adjustment Screw to 1 1/2 Turns Out from Snug and Turn the Screw Out 1/4 Turn. Do the Over Rev Test. Continue this Process Until you have the Engine Over Revving without Struggle.
>>By Adjusting the Carburetor on this Style Carburetor Until the Engine Over Revs without Struggle, you have Adjusted the Air Mixture to the Best Possible Setting.
>>This file was Intended to Give you the Basic Carburetor Cleaning Instructions and May Not Reflect Your Carburetor Components.
>>If you have Questions, Please Ask. The links Below Provide Good Directions on Cleaning the Carburetor. Make sure you use Compressed Air to Blow through all the Carburetor Passages to make sure they are Clear.
>>1- http://www.repairfaq.org/samnew/lmfaq/lmclctc.htm
>>2- http://www.cpdonline.com/692509.pdf .
>>If you Hit a Snag or this Does Not Correct the Problem, I Hope to be Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Be Safe and Happy. Thanks.
Good Luck
Respectfully
John
PS: I am Allowed to Answer 3 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Follow Up Questions are Received Anytime. Comments and Ratings are Greatly Appreciated. Thanks.
Respectfully
John
---------- FOLLOW-UP ----------
QUESTION: I pulled muffler; no Spark Arrestor screen on this model. Blew through muffler - all clear. (I would have tried to start unit w/o muffler, but temps were mid-to-upper 40's this evening & unit will start after 4-5 pulls & did before I removed the muffler). The piston was shiny/smooth (about 3 very faint vertical lines/scratches).
However, you're first question was what flagged me also. I had checked the compression yesterday - 83 psi after numerous pulls & thought this seemed low. Past experience left me with impression small engines normally ran over 100psi. Am I off here? I also wondered whether the colder temps caused something to contract more and breach the vacuum in crankcase????
I do not see any oil/gas seepage around head, crankcase cover, etc - only between muffler-to-cylinder; but again, muffler was clear, so it must have been loose or gasket not sealing well. I did not soaked carb. - will wait for further response on the new data given above.
Once again, only colder temps will prevent unit from starting; temperatures are forecast to drop tomorrow throughout remainder of week/weekend. THANK YOU for responding, for your detail, & the time put forth in answering.
Kevin
AnswerHello Again Kevin:
>>It takes a Minimum of 100PSI for an Engine to Run and Idle Correctly.
>>If the Compression is Lower, then there is a Compression Problem.
>>From your Description it Sounds like the Colder Weather causes the Piston/Rings and Jug/Cylinder to have too Much Clearance and is causing the Low Compression Problem.
>>Once the Engine Starts to Warm Up these Clearances between the Piston/Rings and the Jug/Cylinder Close and the Unit Starts and Runs Better/Correctly.
>>Try Pouring a Small Amount of Engine Oil (1/2 oz) into the Spark Plug Hole (engine cold) and then Try Starting the Engine.
>>If the Engine will Start as Designed (ignore the extra smoking from the muffler), then
>>the Engine Does have Low Compression when Cold and Rings, Piston or a Jug/Cylinder May be Required to Correct this Problem.
>>With the Carburetor Not being Soaked when Cleaned, the Carburetor can Still be the cause of the Problem.
>>As Always, If you Hit a Snag or this Does Not Correct the Problem, I Hope to be Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Be Safe and Happy. Thanks.
Good Luck
Respectfully
John
PS: I am Allowed to Answer 3 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Follow Up Questions are Received Anytime. Comments and Ratings are Greatly Appreciated. Thanks.
Respectfully
John
