No spark - sort of

[BJ73]

Went to start the suzi up today and it just wouldn't fire up, so I pulled out a lead and plug and there's no spark.

But when I put the plug near any metallic body part it arcs to it from the tip of the plug.

I've recently put in a new coil and spark plugs, dizzy cap and leads as well as doing the timing and gap settings, and it was going OK for a while.

Any ideas ? Cheers

[chimpboy]

You're doing it wrong, man.

Don't pull out the plug, just pull out a lead. If you get spark across to a ground point (eg metal part of the body) then you're getting spark.

The spark plug won't spark when it's not screwed into the motor because it's not grounded.

Anyway from the test you did it sounds like you have spark, so you need to look elsewhere.

[-Scott-]

If your spark plugs will spark when earthed to the body, but not when earthed to the motor, that indicates that the motor isn't earthed well.

The fact that it cranks over suggests that it is earthed, so I'm really confused.

I would find your motor earth, disassemble, clean and reassemble just to be sure.

[chimpboy]

If your spark plugs will spark when earthed to the body, but not when earthed to the motor, that indicates that the motor isn't earthed well.

Ah, maybe I read it wrong. I thought he'd just pulled a plug out and tried to get spark with a plug sitting there in the open not next to anything.

[BJ73]

If your spark plugs will spark when earthed to the body, but not when earthed to the motor, that indicates that the motor isn't earthed well.

Ah, maybe I read it wrong. I thought he'd just pulled a plug out and tried to get spark with a plug sitting there in the open not next to anything.

Yeah Chimpboy that's what I did, took a lead off, pulled out the plug, connected the plug to the lead then turned they key = no spark.

That's how I've checked for spark in brushcutters and chainsaws etc, is 4 stroke different ?

Anyway, just the lead to a metal part = no spark, lead + plug to metal part = spark, I'll check for earths tommorow

[chimpboy]

The way I do it is unplug a lead, pull back the insulating cover so the metal end of the lead is exposed, and then jam it somewhere so that the metal part of the lead is 1 or 2 mm away from some bare metal like a bolthead or whatever that is a good ground. Crank it and there should be a fat blue spark.

If that doesn't work, or if the spark is weak and yellow, that's a sign of a spark problem.

To get a spark with the spark plug in place but not with the end of the lead is, from my experience, unusual. But there may be a reason it makes sense that I don't know about, dunno.

My gut is telling me that spark is not your problem though.

[BJ73]

My gut is telling me that spark is not your problem though.

Your gut was right, air is coming out of the intake manifold when I crank it over so I'm guessing the timing belt has slipped a few teeth

[chimpboy]

My gut is telling me that spark is not your problem though.

Your gut was right, air is coming out of the intake manifold when I crank it over so I'm guessing the timing belt has slipped a few teeth

Cool, there's no point having a gut this big if it isn't right sometimes