Spark, compression, fuel. No start

[joe25DA]

Red max 7001 blower. Not a saw obviously but a 2 stroke nonetheless. 165psi, piston is perfect. Sparks to ground and with a tester. Won’t even pop off mix thru the carb. I am leaning to ignition still. Possibly showing thru tester but not enough under pressure at the electrode? The backpack is older but in excellent shape. I don’t mind putting money into it but I also want to isolate the problem. It should pop off a squirt of fuel and it isn’t.

 

[grizz55chev]

Red max 7001 blower. Not a saw obviously but a 2 stroke nonetheless. 165psi, piston is perfect. Sparks to ground and with a tester. Won’t even pop off mix thru the carb. I am leaning to ignition still. Possibly showing thru tester but not enough under pressure at the electrode? The backpack is older but in excellent shape. I don’t mind putting money into it but I also want to isolate the problem. It should pop off a squirt of fuel and it isn’t.

Flywheel key?

 

[Andyshine77]

Yeah look at the flywheel. I had a Shindaiwa that had similar issues, though sometimes it would fire briefly. Spark was strong everything else checked out, finely took apart the kill switch in the handle, while running the vibration was causing the switch to ground, a bit of bending with the needle nose and all was well.

 

[GoBigRed]

So I want to confirm that it sparks with the plug out and laying against something metal. Is that correct? And you said it sparks with an inline tester. But what did the spark off the tester look like? I ask because it’s not uncommon to have a coil that can make enough spark when the plug is out because you are spinning the engine without compression. But once the plug goes in and the engine isn’t turned as fast, the spark is weak and unable to ignite the charge.
Have you tested resistance on the coil? I have no idea what the readings should be but you may be able to find them online

 

[s sidewall]

You using an actual a spark tester or one of those enclosed one that looks like a light flashing when it sparks? Mine looks almost like a spark plug with a clip welded to it. If it don't spark blue with it, then ignition issue. Have you tried a know good spark plug?

Steve from my moto g(7) play using Tapatalk

 

[J D]

Have a really good look over the HT lead... I had a trimmer a while ago that I completely dismantled to get to the flywheel only to find it was fine. Ended up being a pinhole in the lead that would only arc when it was fully in place on the plug... tested fine otherwise & really did my head in until I found it

 

[OM617YOTA]

Does it spark across the gap of the actual plug you're using?

 

[joe25DA]

All good questions. I have not checked the key yet, but it did cross my mind that it could be out of time. Tried 2 separate plugs. It grounds with both. I have both types of testers, cheapo light bulb and a good Briggs one that shows the spark across the contacts. I haven’t used the good one yet. I’ll check the switch but I have a feeling that’s fine.

 

[cookies]

sometimes the flywheel magnets get weak, coil gap? kill switch wires chaffed? flywheel out of time?

 

[Old2stroke]

Gap a spare plug to 0.1" and see if it will fire that in air, if it does, it should fire a normal gap under compression in the engine.

 

[keegantimber]

does it have a spark arrestor in the exhaust? Which could be plugged?

 

[660catman]

does it have a spark arrestor in the exhaust? Which could be plugged?

Been there, done that! It was my issue years ago.


Retired guy from SE Manitoba

 

[joe25DA]

I have a strong blue spark making contact. At this point possibly a shear key and out of time?

 

[grizz55chev]

I have a strong blue spark making contact. At this point possibly a shear key and out of time?View attachment 929597View attachment 929595

Yep!

 

[a. palmer jr.]

I once had this problem with a chainsaw, can't remember which one, but turned out to be the wrong flywheel. It looked good and and had plenty of spark but the magnets were about 1/3 of a turn off.

 

[tomalophicon]

Have you run this saw before? Are you using an 'R' plug?

It may be a long shot but I have a Shindaiwa saw that won't run on resistor plugs but runs fine on non-resistor plugs. The thing shows a bright blue spark with an R plug but still won't run.
Not sure if there's any link to Shindaiwa and Zenoah electronics but you never know.

 

[joe25DA]

I once had this problem with a chainsaw, can't remember which one, but turned out to be the wrong flywheel. It looked good and and had plenty of spark but the magnets were about 1/3 of a turn off.

No one has cracked this open before. All original

 

[joe25DA]

Have you run this saw before? Are you using an 'R' plug?

It may be a long shot but I have a Shindaiwa saw that won't run on resistor plugs but runs fine on non-resistor plugs. The thing shows a bright blue spark with an R plug but still won't run.
Not sure if there's any link to Shindaiwa and Zenoah electronics but you never know.

I’ll have to look. I tried 2 champion plugs, I’ll look and see if they are RCJ8 or CJ8. I’m sure it came with an NGK but I didn’t have that size

 

[Mike Gudgeon]

Have you run this saw before? Are you using an 'R' plug?

It may be a long shot but I have a Shindaiwa saw that won't run on resistor plugs but runs fine on non-resistor plugs. The thing shows a bright blue spark with an R plug but still won't run.
Not sure if there's any link to Shindaiwa and Zenoah electronics but you never know.

Someone kinda almost mentioned it earlier - could be that, under compression, what tests as good sparker is dropping its guts. Possible causes all mentioned earlier.
Substitution is, ideally, handy in situations like this but not always convenient.

Has the flywheel ever been dropped? They reckon sharp impacts can cause a loss of magnetic power. Strange marks on it?
Age too. I know that for a fact 'cos the spritely chicks are harder for me to attract these days.

Anyway, from the sound of your posts you know well what you are doing. Sometimes we just overlook the obvious.

 

[RED-85-Z51]

Blown crank seal. They will show compression but won't blow mix up into the cylinder.

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