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strimmer motor won't start... |
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| message from The Natural Philosopher on 11 May 2004 |
Its an oldy, but apperas to have bags of compression. Simply was in use,
left up for a winter a couple of years ago, never started since.
Its a ltllet 2-0stroke japanese engine - probably about 25cc or so and I
can;t see any spark - the pllug smells of petrol and we even dribbled
some mix into teh p[lug hole, to no avail.
I whipped off the pull handle and discovered something I hadn't seen
since me dads moped curca 1960. A magneto and some contacts. I adjusted
the gap so it was at least closed some of the time and open some of the
time, but still no visible sparks. I removed the wire off the switch
that stops the thing in case this was faulty, and still no sparks.
First of all, is there some way I can identify that there really are no
sparks? I stuck a car strobe light in series with the plug, but I think
this runs off the LT side of the car not the HT...so probably proves
nothing.
Its been years since I fiddled with a magneto, but ISTR that if there is
fuel and a spark these things generally kick a bit and fire if not run.
This ones doing neither.
Is it down to thimgs like stripping out the points and claening them up?
Is there anyway I can use an analogue multimeter to diagnose the problem?
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| Ian Stirling replied to The Natural Philosopher on 12 May 2004 |
<big snip>
Is there any reason to use starting fluid/cans, rather than a
blowtorch pointed into the air intake?
(An unlit blowtorch, for the avoidance of doubt)
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| The Natural Philosopher replied to Ian Stirling on 12 May 2004 |
Yes, its made of plastic :-)
Oh. Best way to start old diesel tractors is to pur fresh diesl in on
the glo plug and let it burn....
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| Grimly Curmudgeon replied to The Natural Philosopher on 13 May 2004 |
It was somewhere around Barstow, on the edge of the desert, when the
An old diesel Landy I had the unfortunate privilege of using
occasionally would only start with a burning diesel-soaked rag held next
to the air intake. Crude but effective.
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| sylva replied to Ian Stirling on 12 May 2004 |
EEzi start type fluids have a fuel in them that will ignite at low
temperature, like ether, so that even if the spark is a bit lacking in
energy the compression can set it away. However because of this very
low spontaneous ignition temperature they "explode" in the cylinder,
this can result in damage to the ring lands. Repeated use, typically
on a diesel engine, "addicts" the engine to starting with them as the
damage to the compression rings means they will never start from cold
unassisted. With SI engines it is similar to forcing the engine to
pink.
Blow torch would typically be propane or butane, these fuels have high
spontaneous ignition temperatures couples with a fairly limited range
of air:fuel ratio under which they will burn. At least with a liquid
fuel there is normally some point in the phase between gas and liquid
where the ratio is OK to start burning.
AJH
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| Mungo \"two sheds\" Toadfoot replied to The Natural Philosopher on 11 May 2004 |
You *can* hold the end of the HT lead while someone gives it a tug. It's not
particularly nice but it won't kill you unless you have a pacemaker or a
weak heart.
The contacts should be clean and as you say they should open and close. They
should open about 25 thou-ish. Is there a small cylinder anywhere with a
lead coming out of it? If so you might need to replace it.
Si
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| Eric Dockum replied to Mungo \"two sheds\" Toadfoot on 12 May 2004 |
I still have a cheap timing light that plugged in series between the
distributor and the spark plug, basically a neon as others have
discussed. Only the fancier ones have a sensor on the LT side.
Also a cheap tool that is essentially a neon bulb. You hold one end,
and, I assume, make a leakage path for one side of the neon. Have the
plug in the engine and the lead hooked up. As someone tries to start
you approach the lead with the other end of the tool. As you do so
the neon flickers if there is a spark power in the lead. Don't have
to touch the spark lead for it to detect. These used to be dirt cheap
in auto shops, I have one in the tool box. You can find which
cylinder is missing on a car engine while it is running without having
to interfere with the system.
This tells you if there is a spark getting to the lead. However the
plug itself may not be good.
Take the plug out and attach to the HT lead. Then lay the plug so the
metal body of the plug is in contact with the metal of the engine.
then try it, and the spark should jump. the return for the spark is
through the body of the plug, and the body of the enginge. I have
also used an old wooden pair of tongs my mum used with a top loader
wasking machine to hold the plug firm against the engine.
If you get nice ble zaps you are fine on that side. The fuel quality
is a good idea, also check nothing has dropped off/come loose that is
giving you and air leak on the inlet side, resulting in too weak a
mixture.
Finally check you have no dead lemmings etc up the exhaust. I bought
a 2 stroke bike years ago that someone sold because there was
something wrong with it. Performed terribly, kept stalling, was
impossible to start etc. There was a perforated pipe up the middle of
the exhaust that was completely plugged with coked oil. I had to get
a blowtorch and chisels to get the stuff off and make it pass gas
again. Put it back on the bike and the performance was transformed.
2 strokes are very sensitive to the exhaust.
eric
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| Ian Stirling replied to Mungo \"two sheds\" Toadfoot on 11 May 2004 |
It'd be a really ****ty way to discover you do have a bad heart though.
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| T i m replied to Ian Stirling on 12 May 2004 |
LOL .. thanks Ian ;-)
T i m
(memories of my Dad doing that to me on an outboard motor .. I
jumped!)
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| Mungo \"two sheds\" Toadfoot replied to Ian Stirling on 12 May 2004 |
news:40A112AB.103@b.c...
:o)
Si
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| mrcheerful replied to The Natural Philosopher on 11 May 2004 |
Make sure that the points actually electrically close.
mrcheerful
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| Grunff replied to The Natural Philosopher on 11 May 2004 |
A wire-end neon across the HT will tell you a lot. If it doesn't even
flicker, then you've got nothing there.
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| Pete C replied to The Natural Philosopher on 11 May 2004 |
Hi,
Try putting the meter on resistance range and attaching it across the
points, it should read some low ish resistance when the points are
open, and a short circuit when the points are closed.
Also measure the resistance between the plug lead/coil HT output and
the cylinder head of the strimmer, it should read a higher resistance
but not an open circuit.
Then measure the resistance between the electrode of the spark plug
and the cylinder head of the strimmer, this should be an open circuit.
Next set the meter to DC volts and connect it across the points, turn
the engine over slowly and you should see the needle kick slightly as
the engine turns over.
Now take a neon screwdriver and put it on the HT output from the coil
while turning the engine over and holding the end of the screwdriver,
it should flash as the engine is turned. Repeat this with the end of
the HT lead.
Now take the plug out and use a straw or thin stick in the plug hole
to identify when the piston is at 'top dead centre', by rotating the
engine slowly and feeling when the stick is pushed out the most. Or
there may be some alignment marks somewhere on the shaft and body of
the strimmer that indicate this.
Then adjust the points until they are only just open, using the meter
to check for this.
Now adjust the gap on the spark plug so it's not too wide. Put the
spark plug on the lead, hold the body of the plug onto the cylinder
head and turn the engine over. With a bit of luck it should spark.
The only other thing on the electical side would be to check the gap
on the spark plug is the right width, or the spark may not be strong
enough. This might be printed or stamped on the body of the strimmer
or maybe a suitable value can be got off the web.
Hope this helps,
Pete.
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| The Natural Philosopher replied to Pete C on 12 May 2004 |
Enormously Pete, thats a good suite of sensible things to try.
Thanks very much indeed.
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| Jim White replied to The Natural Philosopher on 12 May 2004 |
One thing that seems to be more important now than it used to is the
freshness of the petrol.
I drain all my garden tools every year and refill with fresh petrol /
2stroke.
Once you get your electrical probs sorted out, the strimmer still might not
start with 2 year old fuel.
Jim
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| Nick Brooks replied to The Natural Philosopher on 12 May 2004 |
I've got an old petrol strimmer that refuses to start every year despite
having no obvious faults. A quick spray of "Easy Start" onto the air
filter usually sorts it out and once it's going it's fine.
Nick Brooks
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