briggs and stratton 5.5 hp

[Tex]

Model is 12t802.
It has good blue spark, jumps a 1/2" gap, new OEM briggs carb, (carb fills bowl fills up) (primer type), compression test shows 95 psi, flywheel key is good, valves operate properly, new spark plug and it still won't start. Won't even hit on starter fluid.

[38racing]

Does it jump the 1/2 gap with the plug installed? Only thing that comes to mind if all you say is true is that maybe new plug not really good or coil is weak and won't jump an installed plug against the compression while will jump to ground.

[Tex]

Coil was robbed off of a good running engine. I'll try making the spark jump from the plug to ground. thanks

[Tex]

i couldn't get it to arc 1/2" gap from the plug electrode to cylinder head.

[bgsengine]

coil air gap correct? verify the coil laminations and mounting surface has clean ground contact? 1/2 inch is a bit too much gap, really depending on your cranking RPM - note they will need a minimum 250 RPM cranking speed to generate any spark at all. unlikely to be a magnet issue, but within possibility.. are you sure the good running engine's coil is correct for the engine? Some coils may seem to swap in nicely but they may have an incorrect fitment, or different polarity, or different trigger logic (leading or trailing triggers in the ignition module) for example..

[KE4AVB]

I would use the same fuel as the engine intended to start on but I have one question set. Where are you inducing the fuel? At the carburetor or the at the plug? If at the carburetor you may be missing the intake o-ring or have a hole in the intake cross over pipe. I have seen holes rubbed into the backside of the cross over pipe. This why I like to induce fuel at the spark plug hole to make sure it is not an intake issue.

Also what was the donor engine model number? There is at least a couple different coils used in this HP range. Plus just because it is a new plug doesn''t mean it will fire under compression. I have seen plugs to work fine out of the compression environment but but not under compression. It best to use a known good plug for testing.

[Tex]

The donor coil from the engine, the model number is 128T02-1608-B1
and the model number of this engine is 12T802-1569-__ , i cannot make out the last 2 numbers but according to briggs they both use the same 590454 coil.
I cleaned the coil posts it mounts to with sand paper, and cleaned the surface rust off the flywheel, i set the air gap with a business card.
I do remember seeing an O- Ring where the carb mounts to the intake tube, but i will check the intake tube for cracks.
i've tried starting it with fresh non ethanol fuel from the gas tank, then tried spraying through the carb with carb cleaner, and then the plug hole.
I guess i'll take the plug out of the good running engine and try it since it runs flawless.

[Tex]

took the plug off the good engine, installed on the other engine, fired up first pull.
put the now presumed bad plug and put it on the other engine that i robbed the coil off of, and put the coil back on it and it wouldn't start...
and that was a brand new 802592 from Tractor supply.
RESOLVED, bad spark plug.

[Arkie]

A wimpy bad spark plug, even a new one sure can make a guy feel weak upstairs especially after flogging several other more important and costly time consuming things when a engine won't start or run correctly.

Changing a spark plug or plugs is one of the first things I no longer overlook due to what you seen or worse.
Had a recent experience with such and seems most times it's a champion plug.
Chainsaw was starting a running good, next day when i hauled it too the woodlot it would only briefly try to start then eventually no promise at all.
Set the saw aside and used my other saw rest of the day.
Tried to start the bad saw later and no go, acted like no getting enough fuel, maybe carb issue.
Next day on the workbench I briefly eyeballed the fuel line and was thinking maybe carb kit but stopped immediately and changed the little champion spark plug. Fired right up and ran great with new plug.

Little wimpy spark plugs (usually Champion) had made me feel really weak in some previous experiences with engines.

[KE4AVB]

This is why I suggest using a known good plug as have even gotten bad NGKs right out of the box. Not very often but is happens. I even had a CMR6H that caused a Stihl hedger to diesel last Spring. Considering plugs are mass produced and are shipped there is always numerous times they can be dropped.