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Stihl 420 will not start

Discussion in 'Mechanic and Repair' started by khutch, Aug 3, 2008.

  1. khutch

    khutch LawnSite Senior Member
    Messages: 495

    Stihl 420 blower will not start unless I try this old trick, dip plug in gas and it will crank up, and then will run for a re-start or two. I did the usual plug, filter check etc to get it to run in the first place....
    Why does the dipping in gas work so easily? And does removing the fuel filter work for testing purposes (clogged) or does it mask the problem or create another?
  2. echoman8

    echoman8 LawnSite Senior Member
    Messages: 293

    There are a lotta things that can make a small engine hard to start.

    More detailed info is needed to find the problem, but to answer:

    Why does dipping plug in gas work? the combustion chamber of the motor is not getting fuel as it is supposed to. You are bypassing the fuel delivery when putting fuel on plug. Choke not working ----- air leak in hoses, gaskets, seals, manifold ......----- fuel restriction at filter, internal carb screen, metering lever setting in carb.

    Does taking fuel filter off to test work? If the hose is left in the tank with no filter, it will draw any contaminants into the carb. It takes very very little crud to block the internal carburetor screen.

    TO DO THE FOLLOWING, ALLOW THE FUEL FILTER TO DRY WITHOUT USING COMPRESSED AIR. Place the nipple of the filter to lips and draw. If there is resistance, get a new filter. I have been unable to clean a filter with solvent and air compression to the degree that it will continue to filter very long.

    Good luck

  3. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    As for the fuel filter, if you wish to troubleshoot this just replace it, no offense but if you're already removing the old one...

    They're only a few dollars...
  4. echoman8

    echoman8 LawnSite Senior Member
    Messages: 293

    Hi topsites.

    You are absolutely right about buying a new fuel filter.

    I look at things different because I live 40 miles from the closest small engine dealer with parts. I live on making something work "one more day" without taking that long trip.

    So, please excuse me I seem to make a simple repair hard.

  5. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    I'm not a total jerk in that regard, I don't even like driving the 8 miles to my dealer over a stupid 2 dollar part, it's more the principle of wasting fuel and time than doing it right, I am just as fast to try a trick too so I don't have to leave home.

    But this crap frustrated me too many times...
    So what I ended up doing is ordering something like 20 or so of those silly little in-tank filters,
    now I always have a new one around if I need it :p
    I've also got about as many of those in-line filters, among other parts like bushings and stuff.

    It took years to build it up, but every time I had some money or whenever I needed a part I
    would buy more than one, also I didn't buy them ALL from the dealer (price) so that helps as well.

    One builds up inventory that way, I just work on it one part and one day at a time,
    then one day what do you know, I must have 5 or 6 thousand dollars worth of parts by now :p
    But everyone starts somewhere, one day, one part at a time.

    That helps me out a LOT!
    I am usually able to fix most problems at home.
    Matter of fact, back in the old days when stuff broke down I always went straight to the dealer.
    Nowadays home is the first place I take it to anymore :p

    Just a thought, maybe it helps you or someone else.

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