# 18 hp Briggs No spark



## Arkie

Exact same spark issues as this guys previous post. Also see gas spurt up thru carb intake sometimes when cranking, but this seems to be normal as engine runs and starts good when it gets spark. 
Same model number engine.
http://www.tractorforum.com/f166/18-hp-briggs-no-spark-17195/

Seen on you tube that the two ignition wires need to be connected in certain order would reversal result in mag failure.
Engine ran fine when run for about 20 seconds with cowling removed when new coil was first installed, killed engine and no restart. Now new coil is not firing.
mag coils are $45-60.

Any ideas??????


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## wjjones

Is the coil kill wire in the correct place? It could be grounding out the coil.


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## jhngardner367

If it doesn't run when the cowl is in place,but will if the cowl is removed,then the cowl could be shorting something out.
If the coil was using points,previously,and you got the new style coil, it will do this if the wire from the points is used,so make sure to NOT connect it.


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## Arkie

*ignition issues with 18hp briggs twin*

Kill wire is disconnected.
Installed new mag ran for about 30 min and wqhen I killed the engine no re-start.
Installed another new mag under warranty.

Tested with kill wire disconnected from the tractor, just dangling.
Ran for 5 min and I purposely killed the engine using the one kill wire.
No respark after killing. Removed air cowling and removed kill wire from coil mag terminal Still no fire. Appears mags are weak and wimpy.
I ordered and new style mag from ebay for $17. (time to try different brand of magneto coil. This is newer style engine that has never had points one magnet on flywheel and magneto coil outside and air gap speced at .010 to .014.

Will re-test in about week and let you know the results.


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## jhngardner367

Post a pic of the setup.


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## Arkie

I'll get back after I've stested with the other parts, both new and used stuff.


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## 68plymouth383

Do you have any updates on your spark problem?


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## jhngardner367

Usually,if the post isn't answered in 6 months,they aren't coming back to it.


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## Arkie

68plymouth383 said:


> Do you have any updates on your spark problem?



Briggs and Stratton opposed twin hands on experience that not seen in my service manual.

I seen some opposed Briggs mags on ebay for like $16 dollars total and bought two and they work great. One thing I also discovered is the ebay mags are directional. If mounted wrong no fire. (their is a leading and lagging leg on the laminations for correct operation) If no fire with .010 spacing turn the coil over and try again. Spark plug wires using the ebay mags when correct leave the top of the engine going in opposite direction from the spark plugs and the plug wires have to be installed correctly on 1 and 2 cylinders. The shortest lead goes to the spark plug on same side of the engine as the mag coil. (the shortest wire will just barely reach the closest spark plug when using the flea bay mags and the coil turned what appears to be backwards.
I'm not sure about the Napa mag, but would most likely be the same symptoms if mounted wrong. Summary: If no fire when cranking with a new mag turn it over and re-test.
I'm running both the Napa and the flea bay mags on some lawn tractors and they are all running ok with no failures.
Here is the e-bay type I purchased.
260704467127

Napa gave me a new warranty replacement mag (they said it had a year warranty) it works ok now. Guess the Napa mags were just weak, one of the bad mags Napa gave look used???

These Briggs opposed twin mag coils I suspect have a solid state control inside and do not fire both spark plug leads at same time like the old opposed cylinder twin tower Onan engine coils.


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## jhngardner367

The Briggs opposed -twin engines use a "wasted spark" ignition system.
Both plugs fire at the same time,whether the piston is up,or down.
Most mags will have the word"out",or "engine side" on them,and yes, they are directional. Air gap is usually 0.010 ".
I've only had problems with 1 after market mag,and that was due to the fact that the factory never used epoxy to bond the wires into the mag. It was returned,with out a problem.
Wire routing is important,as well. If it is routed wrong,it is either not long enough,or it is too long,and will get damaged easily.
I advise people to snap a picture of it,BEFORE removing it,so it can be routed properly.


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## Arkie

jhngardner367 said:


> The Briggs opposed -twin engines use a "wasted spark" ignition system.
> Both plugs fire at the same time,whether the piston is up,or down.
> Most mags will have the word"out",or "engine side" on them,and yes, they are directional. Air gap is usually 0.010 ".
> I've only had problems with 1 after market mag,and that was due to the fact that the factory never used epoxy to bond the wires into the mag. It was returned,with out a problem.
> Wire routing is important,as well. If it is routed wrong,it is either not long enough,or it is too long,and will get damaged easily.* If the spark plug wires do reach the spark plugs when reversed the engine won't start and run. (I tried several connections and only one way to make the Briggs Opposed twin mags operate the engine and several wrong ways.*I advise people to snap a picture of it,BEFORE removing it,so it can be routed properly.


 *Right, very good idea about taking a picture before removing a Briggs mag, but I think the napa spark plug wires and the ebay mag coil wires were facing opposite directions for getting a run but not sure. Point is, If a new replacement Briggs mag coil don't fire try flipping it upside down and re-test!*
The spark plug wires on the old point type dual tower Onan coils could be installed on either of the two cylinders. I've actually used two separate GM automotive coils as a temp replacement to make a Onan gen engine run on both cylinders until a Onan dual tower coil could be found.. The spark plug wires on the Briggs opposed twin are cylinder specific. Engine won't run if they are reversed. Also Briggs opposed twin l-head won't run if one spark plug wire is connected to both plugs even thou its waste spark and both plugs firing from a single mag lead.


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## jhngardner367

It is specific,in that the pick up,or trigger,in the mag,must be positioned properly,since it is a fixed-timing system. If the mag is installed"upside down",it can't trigger properly.
As for one wire connected to 2 plugs, no,it won't fire properly,due to the extra load.It weakens the spark too much.
Briggs states that to check for a defective coil,you should run the engine at mid,to full throttle,and carefully take off one wire. It should have a noticeable drop.
Replace the wire,and repeat for the other side. It also should have a noticeable drop.
If it dies out when EITHER wire is taken off,then the coil is bad.
The Onan,and Kohler engines usually had a Battery/coil ignition,where voltage powered the coil.
On Briggs,Tecumseh,and others(including the newer Kohler),they use a magnetic- induction coil.


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## Arkie

jhngardner367 said:


> It is specific,in that the pick up,or trigger,in the mag,must be positioned properly,since it is a fixed-timing system. If the mag is installed"upside down",it can't trigger properly.
> As for one wire connected to 2 plugs, no,it won't fire properly,due to the extra load.It weakens the spark too much.
> Briggs states that to check for a defective coil,you should run the engine at mid,to full throttle,and carefully take off one wire. It should have a noticeable drop.
> Replace the wire,and repeat for the other side. It also should have a noticeable drop.
> If it dies out when EITHER wire is taken off,then the coil is bad.
> The Onan,and Kohler engines usually had a Battery/coil ignition,where voltage powered the coil.
> On Briggs,Tecumseh,and others(including the newer Kohler),they use a magnetic- induction coil.


I seen a electronic diagram drawing somewhere awhile back showing two completely separate electronic sensor trigger control and two separate HV mag coils inside the Briggs twin magnetos. (should have printed) I think it was from this site http://ppeten.com/forums/index.php
I have two Briggs twin mag's that only produces fire to one cylinder and if tested with a ohmmeter per the manual the ohms readings look normal for the HV windings and for the kill wire. Appears that ONE of the electronic mag trigger circuits is bad inside the magneto. I've found for me it's more user friendly instead of pulling a plug wire off when testing for good ignition to both cylinders, to ground out each spark plug tip one at a time and check for rpm drop on each cylinder. (use a tool that has a good insulated handle so as to keep your depends undies dry) I try not to purposely pull a spark plug wire off when a engine is running on a electronic type ignition system. (The HV don't have anywhere to go except backwards or into your depends undies, again)


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