Strange ignition problem.

[psdonald42]

Hello,

I have a pressure washer with what I think is a Tecumseh engine.
Failed to start and there was no spark. Ordered a new coil as they ae pretty cheap these days and i didn't want to mess about.
Stll no spark. This is a simple engine. No points or condenser, just a cut off wire. With the wire disconnect still no joy.
Cleaned up the ground path., nope.
I was messing about spinning the flywheel by hand (no gas at this point) and noticed that i got a spark when I spun the flywheel CCW and not CW.
I refitted the old coil and got the same result!
Of course the engine runs CW.

Has anyboybody seen this or have any ideas?
I know the magnet (which feels strong) has a north south bias but it's never been touched and is fixed on the flywheel.

Beats me.
(New coil, new sparkplug, no cutout wire, clean ground)

Please save me
Peter

 

[bertsmobile1]

Try putting the new coil on the other way round

 

[psdonald42]

Hello Bert.
The holes are not equally spaced and only go on one way. Old and new.

 

[bertsmobile1]

The Hall effect triggers are polarity sensitive.
It is not unheard of for a magnet to reverse polarity if stored under the correct conditions which is why new ones come with a keeper plate on them.

 

[psdonald42]

I was under the impression that the coil was just a coil with low and high voltage coils. Hall effect transistors are low voltage and are triggered by magnetic field. do you have a typical circuit diagram?

If the Magnet has flipped is it possible to replace it? I can't see any being sold unless as part of a new flywheel.
Peter

 

[bertsmobile1]

The Atom module or a Magnatron or any other "points eliminator " is a Hall effect trigger.
Google them and you will find circuit diagrams from the very simple to the extremely complicated with reducing amounts of retardation to effect an advance of the spark.
because they work on the voltage generated in a coil and because the wavefront will start off either negative or positive depending upon the polarity of the magnets the triggers are sensitive to the polarity of the magnets .
When the triggers were first introduced they had resistors transistos & diodes soldered onto a board and were external items like you have there.
Now days the same circuitary can be burned into a chip, small enough to be emedded into the potting mix so the external units were replaced with internal ones and $ 5.00 coils became $ 40.00 modules

I am no B & S expert in any way shape nor form but have found out that on some of the older points engines, you can fit a modern "module" back to front & it will work

 

[StarTech]

Need engine numbers to see what your setup is. and also need to which coil you ordered.

 

[psdonald42]

Great response. Who knew how complicated these things are. I'm an electronics engineer but had no idea i would need that on a small engine.

As i said before the coil only fits on one way due to offset screws. I will look at flipping it if i can. Rainy day so it might be time.

 

[psdonald42]

OK. I elongated the holes and got the new coil to fit upside-down. Guess what... the spark is still only CCW.

Peter

PS the engine is on a campbell hausfeld PW174901LE pressure washer. Not sure the actual engine.

 

[Hammermechanicman]

Left handed engine. Very rare. Will only work in the southern hemisphere.