re-mculloch petrol mower

[joesoap1]

Hi Guys, my Mculloch rotary mower is driving me mad. It's only 5 years old, but had trouble since year 1 with starting. It's electronic ignition.I've just stripped carb down, diapragm looks fine, cleaned it all out, but still wont start. It ran for a few weeks , then wouldn't start, this has been an off/on for ages.resort to 32 year old hover then.
Wonder if it's Coil,??? £39, to buy, but, haven't got a proper spark tester.even when I tried to see spark the old way, it showed nowt, but then decided to fire.I don't want to buy a coil and find it's some thing else.Thought these were solid state, infallible?
checked high tension leads, not loose. new plug, changed oil, shop want's £80 to change coil , IF it is that. Any advice welcome; XC40 Sprint, self propelled,briggs stratton engine, ruddy useless.my old mountfield lasted 15 years, till body fell apart, but engine lovely.

 

[Burnerman]

I have to say, the main problem with these, or any Briggs engine with the tank under the carb, is the diaphragm between the carb and the tank.
Due to the ethanol prescence in fuel these days, the diaphragms quickly start to break down and perish, so I'd definitely pop one of those in.
They are in a two piece set - the diaphragm goes to the tank and the gasket is on top. If the carb has 6 screws holding it on, then the part number should be (Briggs) 795083.
When you have the carb off, check the filter on the end of the 2" dip pipe for blockages.
I'm not saying the igniter is not at fault, but if it does fire then thats unlikely.
John

 

[joesoap1]

I have to say, the main problem with these, or any Briggs engine with the tank under the carb, is the diaphragm between the carb and the tank.
Due to the ethanol prescence in fuel these days, the diaphragms quickly start to break down and perish, so I'd definitely pop one of those in.
They are in a two piece set - the diaphragm goes to the tank and the gasket is on top. If the carb has 6 screws holding it on, then the part number should be (Briggs) 795083.
When you have the carb off, check the filter on the end of the 2" dip pipe for blockages.
I'm not saying the igniter is not at fault, but if it does fire then thats unlikely.
John

Hi John, thanks for reply, the diaphragm isn't perforated,both parts, looked perfect, the mesh also was clean,tube also, thourouly cleaned it, and tank.
I followed a You Tube video, to do it, it was simple, exactly as you said.Took all the housing off, to see ignition and high lead, all seemed fine, but, no sign of firing.Arms aching pulling it
It did it before, then just fired, and ok for a few times, then no start again
.I 'm like you, I thought the igniter would fail or not,but without the spark tool £16 , hard to say, without it, there's no moving points is there..
I 've tried it in dark garage, and cannot see a spark, but, it fired up weeks later.Spending £70 + on it hardly seems worth it, even though it's not old.

 

[kbdiy]

I'd still go for the diaphragm replacement to be sure. It's a cheap easy fix and worked wonders on my mower.

Got mine here http://www.briggsbits.co.uk/

 

[Burnerman]

If you want to go down the igniter route, then try GHS on ebay......coils are less than £30 and dead easy to fit. At this time I wouldn't suspect the igniter but typically they provide sparks that are easy enough to see so thats only a guess.
You can get a diaphragm set there too.
John

 

[Burnerman]

I'd still go for the diaphragm replacement to be sure. It's a cheap easy fix and worked wonders on my mower.

Got mine here http://www.briggsbits.co.uk/[/QUOTE]

Curious thinks, these diaphragms......they can cause a no start or alternatively make the engine run as if it was on full choke.
Its reckoned they last only two years due to ethanol content in petrol.
John

 

[joesoap1]

I'd still go for the diaphragm replacement to be sure. It's a cheap easy fix and worked wonders on my mower.

Got mine here http://www.briggsbits.co.uk/[/QUOTE]thanks guys, I will try new diaphragm first, was yours visibly defective ?
petrol getting through, because, plugs wet.

 

[joesoap1]

If you want to go down the igniter route, then try GHS on ebay......coils are less than £30 and dead easy to fit. At this time I wouldn't suspect the igniter but typically they provide sparks that are easy enough to see so thats only a guess.
You can get a diaphragm set there too.
John

Hi, I cannot see a spark, even getting son to pull , and me holding plug with pliers in a dark garage?
can they be intermittent?

 

[Burnerman]

Sure, igniters can fail, but I don't get through so many personally - and those I do are often Stihl
No worries......try another plug, and then try the lead alone to spark across something like a cylinder head bolt which is a good earth. In free air, the gap should easily jump 5mm.
Just regarding the diaphragm, the material tends to swell a little and go floppy.....the bit that actually does the action are the 2 'U' shaped flaps, which are valves in their own way.
John

 

[joesoap1]

Sure, igniters can fail, but I don't get through so many personally - and those I do are often Stihl
No worries......try another plug, and then try the lead alone to spark across something like a cylinder head bolt which is a good earth. In free air, the gap should easily jump 5mm.
Just regarding the diaphragm, the material tends to swell a little and go floppy.....the bit that actually does the action are the 2 'U' shaped flaps, which are valves in their own way.
John

Thanks John, just ordered a diaphragm online.tried 2 plugs, new. same;when I first had it, if it stopped, couldn't get it going again until I waited 20 minutes or so.Always tied the deadmans handle when moving from lawns so it didn't stop.been a pain since new.
Stihl.My hedge cutters Stihl. supposed to be the best.
see what happens when I change it.

 

[joesoap1]

Sure, igniters can fail, but I don't get through so many personally - and those I do are often Stihl
No worries......try another plug, and then try the lead alone to spark across something like a cylinder head bolt which is a good earth. In free air, the gap should easily jump 5mm.
Just regarding the diaphragm, the material tends to swell a little and go floppy.....the bit that actually does the action are the 2 'U' shaped flaps, which are valves in their own way.
John

Thanks John, just ordered a diaphragm online.tried 2 plugs, new. same; just tried it twice with different plugs in air, not a blink in the dark;;
when I first had it, if it stopped, couldn't get it going again until I waited 20 minutes or so.Always tied the deadmans handle when moving from lawns so it didn't stop.been a pain since new.
Stihl.My hedge cutters Stihl. supposed to be the best.
see what happens when I change it.

 

[joesoap1]

Sure, igniters can fail, but I don't get through so many personally - and those I do are often Stihl
No worries......try another plug, and then try the lead alone to spark across something like a cylinder head bolt which is a good earth. In free air, the gap should easily jump 5mm.
Just regarding the diaphragm, the material tends to swell a little and go floppy.....the bit that actually does the action are the 2 'U' shaped flaps, which are valves in their own way.
John

Thanks John, just ordered a diaphragm online.tried 2 plugs, new. same; just tried it twice with different plugs in air, not a blink in the dark;;
when I first had it, if it stopped, couldn't get it going again until I waited 20 minutes or so.Always tied the deadmans handle when moving from lawns so it didn't stop.been a pain since new.
Stihl.My hedge cutters Stihl. supposed to be the best.
see what happens when I change it.

Hi Guys, on the spark plug lead, how does is the cap end fitted to the lead? and how does one remove it, to check for spark on head bolt, without plug ?

 

[Burnerman]

Careful with this one - it isn't the screw in type that you may expect.
The connector to the plug is stuck either into the end or the side of the HT lead, and the whole thing is kept together by the rubber cap.
Leave it be if you can.....if you want to test for a spark, shove a screw or bolt or similar in the place of the spark plug, and use that.
John

 

[joesoap1]

Careful with this one - it isn't the screw in type that you may expect.
The connector to the plug is stuck either into the end or the side of the HT lead, and the whole thing is kept together by the rubber cap.
Leave it be if you can.....if you want to test for a spark, shove a screw or bolt or similar in the place of the spark plug, and use that.
John

Hi john, thanks for reply, appreciate it.
Put a bolt in because both plugs giving no spark at al, held against body bolt..
Using a bol tin boot end,,BUT my wife holding lead end, she says spark is coming from lead as it enters boot end.Cannot see myself, as she cannot pull it
So it is sparking, wonder if boot end connection is dodgy, or duff new plugs?
edit, just tried again using cleaned plug, spark still at lead as it goes into rubber grommet at boot end, not plug .also, I can turn boot end on lead end, not tight enough to twist lead??

 

[Burnerman]

Obviously the high voltage electricity is finding it easier to track back along the HT lead, rather than to fire at the plug......this could be due to a perished HT lead, or maybe the plug connector (wire spiral) inside the boot isn't making contact with the HT lead inner core.
I'd carefully pull the boot free - its really just held by itself and the fact that the HT lead and plug connector are at right angles to eachother.
Feel free to test or run the engine without the boot in place, if you want.
John