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JohnFornaro

No spark in 7116. What did I break?

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JohnFornaro

Well, I got my 7116 carburetion problems worked out thanx to you guys, and I was feeling proud to have revived this workhorse. So yesterday, I attempted dragging a twenty foot long 16" diameter poplar up to the garden to its final resting place as a terrace. The 7116 spun its rear wheels & created a divot. I backed it up and ran forward. There seemed to be a squeak, and then the engine died. No spark.I used the 3416 to drag the two now 10 foot logs into terrace position in the garden. I shouldn't have tried to push the 7116, but hey. See foto.In the past, I have stalled out the 16hp Briggs by overloading, but after a brief respite, it started up again. This time it didn't.Problem is, I don't have points on this engine, and it has a solid state voltage regulator.Question #1: What did I break?Question #2: How can I get it started again?I read this article, but it's more geared to an engine with points:http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=68865

Poplar-Terrace-11-08-15.JPG

Poplar-Terrace-11-08-15.JPG.bfa4b3c987c64161503dbe7456e7abe0.JPG

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dentwizz

On a Magnetron briggs(no points) there should be no 'strain' related failures for normal use without impact(like a massive blade hit). If it made a sound like a squeak or a chuff as it quit I would check valve clearances or ring compression. You can fairly simply check for that by running the starter. If it definitively kicks with each compression then that's probably fine. If it does not kick and just spins easily there is likely a compression loss in the system, either valves or rings.

Is the spark plug still clean? The Briggs is pretty tolerant of bad mix settings that can black out a spark plug. To the untrained eye the result is running til it quits. If the plug is black, I would replace it and retest but lean the mix a little. If the plug looks good, break out the spark checker and see what it says.

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powerking_one

If this engine does have the B&S Magnetron on it, even if the flywheel key got sheared, you would still have spark; it just wouldn't start/run. If it still had points in it with a sheared F/W key, then you probably would have no spark (depending on how far the keyway/timing is off; necessarily).

Tom (PK)

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JohnFornaro

Thanks for the detailed answers there!

Still, there is no spark. Starter turns over the engine at the right speed, with no weird noises, carb squirts gas.

Plug is clean, that light brown or tan color that I've come to expect. The spark plug "test" was classic. "Classic" being what I always do. Remove the plug, re-attach the wire, hold the plug "arm" (never could remember if it's the cathode or anode) against the engine block, and expect a spark to jump the gap while turning over the engine.

Every once in a while, I run into problems which "fix" themselves the next day. So I will be going out there in the rain, I guess, to see if it will start this afternoon.

Anyhow, thanks again!

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PhanDad

Whenever a magneto equipped engine just quits for no apparent reason, I always suspect a grounded mag. There's lots of places for the "kill" wire to get skinned, etc and go to ground.

Disconnect the kill wire and check for spark.

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PhanDad

If your 7116 Briggs doesn't have points, then the kill wire is probably hooked to an insulator where the points are located in earlier engines. It should look something like this (sorry for the poor quality pic):

KillWire_11a.JPG

In the pic, the red wire is from the ignition switch. The small black wire goes under the tin to the coil.Or if the Briggs has points, the kill wire is hooked to an insulator that's mounted on the top screw of the points cover. It should look like this (another poor pic as the gas shutoff valve blocks the view of most of the insulator):

IMG_8975a.JPG

Again, the black wire goes under the tin to the coil, the white wire is from the ignition switch. If disconnecting the ignition switch kill wire doesn't allow spark, try wiggling the black wire under the tin, it might be grounding out.

KillWire_11a.JPG.18a6272c4d340e252959ca5d1593a9de.JPG

IMG_8975a.JPG.8daf424f5ca2ac69aa7e1b576d2eeacd.JPG

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JohnFornaro

PhanDad:OK. This Briggs does not have points, so I'll refer to your top pic. The red wire goes to the ignition switch. Is that one the kill wire? About the small black wire going to the coil. Do you mean the coil of the Magnetron? This Briggs doesn't have a "coil" like a generator/starter Briggs with points does.In my engine, there are two black wires at the insulator. The lower one goes to the headlights. The upper one goes under the tin.Here's a pic:

Briggs-Kill-Switch.jpg

Briggs-Kill-Switch.jpg.1f8fc68a99720c83afc502c035387235.jpg

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PhanDad

The black wire running vertically up to the insulator is the "kill" wire from the ignition switch (it goes to ground when the ignition switch is in the "off" position). The other black wire from the insulator that goes under the tin connects to the magneto coil to kill the spark.

Unhook the vertical black wire from the insulator and see if you get spark. If you do, then the wire from the ignition switch is grounded somewhere. If you don't, then wiggle the wire that goes under the tin and try for spark. If you get spark, then the wire that runs under the tin is grounding somewhere and you'll most likely have to remove the tin to permanently fix it.

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theniteowl

If you find that your kill wire is grounding out it could be one of the safety switches malfunctioning. I have had this happen on a couple of tractors. The switches ground out the kill wire until their particular needs are met like sitting on the seat, putting the transmission in neutral or fully pushing down the clutch/brake, etc.

On my B-112 the switch for the hydro transmission is very picky. Sometimes I have to put it at the neutral point and then wiggle it back and forth until it hits just right.

On your engine is 12 volt required somewhere like it is to an external ignition coil on other engine types? I found this to be a problem on an Allis 716 recently. No voltage is making it to the plus side of the coil and as soon as I put a jumper on it from the battery to the coil it would fire. Could be a bad/loose connection at the key switch or the wire broken somewhere along the way to the coil.

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JohnFornaro

Kill Wire it is! Started right up. The insulator connector is a bit weird, tho... Needed a 9 mm wrench and a needle nose vise grip to loosen. Some NATO standard, no doubt!

So.... Do I replace the ignition switch by default, or go into the innards under the dashboard to replace the kill wire?

Also noticed that under the grime, this wire goes to the headlite harness, but turns back to the ig-switch. Couldn't see under the grime.

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theniteowl

Somewhere along it's path the wire is being grounded when it should not be. If the harness is original and unmolested then the most likely cause is one of the safety switches. You should be able to locate and disconnect them one at a time to troubleshoot the problem.

These switches apply a ground to the kill wire whenever the switch is in the position indicating an unsafe condition. For instance, a seat switch is making a ground connection any time there is no pressure from someone sitting on the seat. When you sit it pushes in the pin that disconnects the ground connection. By unplugging the seat switch you remove it's ability to apply a ground to the kill wire then if you crank the engine over and it fires you know the switch is malfunctioning by either being internally shorted to ground, stuck in the grounded position or just not in the correct position for pressure on the seat to push the plunger down.

The issue could be at the ignition switch but it is less likely.

Do you have and know how to use a multimeter? They are cheap to buy and easy to use with little instruction. It would come in very handy diagnosing these issues.

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JohnFornaro

NiteOwl! Thanks for the suggestion.

I disconnected the seat switch shortly after I acquired the tractor, around 1992-ish. The only other switch I could check is the forward/reverse lever switch.

The process, then, is, disconnect the safety switch, reconnect the kill wire, try and start the tractor? If that is the case, replace or disable that switch and I'm good to go.

Otherwise, I need to find where the kill wire is shorted out. I can't figure the continuity thing. The conductor in the kill wire is presumably not damaged, so it would be continuous. The test being, there should be no continuity between the kill wire and the tractor frame? What do you use for current for the test?

I do have a BK 2860A multimeter.

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PhanDad

Your tractor is probably a mfg#1691382. This is the wiring diagram for that tractor:

16GTHL_Wire7116b.jpg

Ignore the scribbles; they were my notes when I installed a Briggs into a 17GTH-L.If I understand the symptoms your tractor exhibited before discounting the kill wire (mainly tractor would turn over, but no spark), the safety switches and associated wiring are OK. I say this because if you look at the diagram, for the solenoid to close and crank the engine, the 3 safety switches (seat, tranny, PTO) must be satisfied (closed to allow a ground path for the solenoid). However, the tractor also has an interlock module that can cause the engine to shutdown by using the "kill" wire if the tractor isn't operated in what is deemed a "safe" manor. These modules can fail in various states, and can fail such that the "kill" wire is always grounded through the module. Bottom line is the interlock module or ignition switch has failed or any part of the "kill" wire from the ignition switch or interlock module to the insulator tab is going to ground. The interlock module is behind the battery under the dash. I don't know exactly what it looks like, but if it's similar to the more complicated modules that came with the Command Sovereigns, it's a block lump about 1"x1"x2" with wires that connect to a multi wire connector that in turn is connected to the wiring harness. First thing I would do is to disconnect the interlock module and see if you then have spark. If you so, you could leave the wiring this way but additional safety features would no longer work. DO THIS AT YOUR OWN RISK. Without the module active, after the tractor is started, it will run regardless of conditions like an old FDT.If disconnecting the module doesn't resolve the spark issue, then you have to find the ground problem. As theniteowl suggested, a multi-meter to check ground continuity would be the tool needed to find the problem.

16GTHL_Wire7116b.jpg.b54a3948a8f834277973f5273afc87c6.jpg

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PhanDad

Just read your post about "I need to find where the kill wire is shorted out", some thoughts.

As for testing with the multi-meter, you use the "ohms" setting looking for resistance (the "ohms" setting provides some small amount of current). Usually the black lead is connected to ground and the red lead is used for testing. Disconnect one of the main battery leads (usually the ground) so you don't inadvertently damage anything.

So to test the ignition switch for example, disconnect the wiring connector. Test the "M" pin; with the switch "off", the pin should show zero resistance since in that position you want the kill wire grounded to shutdown the engine. Turn the switch to the "on", the ground should disappear and you'd have infinite resistance. IF YOU HAVE DISCONNECTED one of the battery leads, you should also test the "start" position, you don't want the "M" pin to be grounded in that position either.

To test the entire "kill" wire, you need to disconnect it from the ignition switch, the interlock module, and the insulator terminal assuming I'm reading the correct wiring diagram. With it totally disconnected, the resistance should be "infinite" between the wire conductor and ground. If not, the wire conductor is touching the frame, etc somewhere. Usually it's easier to run a new wire from the ignition switch to the insulator (and the safety module if you choose to keep it functional).

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JohnFornaro

PhanDad: Bingo! 1691382 it is. And on page 3-27 of my LFGT "Service & Repair Manual", Rev 4, 2001, there is the chart you included in your post.

I think the tractor is 1982 vintage. A reasonable person like me would expect there to be information on the interlock module in the 2001 manual, but like so much else in repair manual department, there is no help for what you really need. Rather, the manual seems as if it were more an example of a visually nice presentation of technical repair information culled from older texts by a novice who did not really understand how these tractors work, and what could go wrong with them, and how to fix them. But enough ranting.

I'm surprised that I haven't triggered the interlock module (IM) years ago. I push these tractors to their physical limits as mentioned in my OP, and can be often seen using them in an "unsafe" manner. Dragging a 20' log, 16" in diameter, going up a 20% slope ain't "safe", I'm figgering.

Remember, in my original post, I said, "There seemed to be a squeak, and then the engine died". So the tentative diagnosis of the IM failure seems apropos. After all, the other safety switches work as they should, per your observation and my demonstration.

To test its failure, then, I would reconnect the kill wire, disconnect the IM, and see if the tractor starts. By my read of the electrical diagram, I have a 5 pin ignition switch, and if the IM is out of the circuit, any of the other three switches could ground if not satisfied, killing the engine. I'm not sure which is the kill wire in the diagram.

Can the IM be reset?

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PhanDad

The "kill" wire is the wire that runs from the "M" (magneto" terminal of the ignition switch to the magetno via the insulator tab. The IM also ties into this wire to kill the engine if the IM thinks there's an unsafe condition.

The IM should "reset" itself when the offending condition is corrected. For instance if the PTO is engaged, and your butt leaves the seat, the "kill" wire goes to ground and the engine shutsdown. But if you sit back down quickly, the IM is "happy" and the IM removes the ground and the engine gets its spark back. On one of my tractors that doesn't have the IM removed, this happens when I shift my weight to the side of the seat when sideways on a slope. The IM can not be manually reset.

When the IM is removed from the circuitry, the other safety switches will not shut the engine down because they are only in the solenoid "start" circuit and will only stop the engine from cranking (like the older tractors). Once running, the tractor operator supplies the logic for what is unsafe and shutting down the tractor.

Until further testing any of the problems listed in my earlier post could be the problem (ignition switch, IM, wire rub to ground).

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PhanDad

PS - the IM senses data from 2 spots along the path to ground of the safety switches. First is there ground at the solenoid terminal - meaning the tranny is in neutral, the PTO is off, and there is a butt in the seat.

Second is there ground present on the upstream side of the seat switch - meaning there is a butt in the seat.

From this info the IM shuts down the spark as described in the operator's manual for what are deemed unsafe conditions. This is independent of the engine cranking logic which is controlled directly by the switches.

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JohnFornaro

Woah.

What you're talking about has to do with the connection from between the butt switch (BS, naturally) and the tranny switch to the IM, as shown in the schematic.

The schematic shows, from bottom up, center switch, tranny switch, and BS in series to ground. I have defeated the BS, but the ground must be continuous, because before the log incident, the other switches worked properly. I don't get the schematic from an electrical standpoint.

I need to study this more before I fully understand it, including your testing paradigm up above, I guess, starting with tracking down the kill wire and its relation to the magneto.

So, following the Latin adage, ubi dubi ex flagellum, (when in doubt, whip it out), I whip out my B&S service manual for 1919-1981 engines. Which I'm hoping would pertain to a 1982 engine.

Page 53, Fig. 735, illustrates the 10 or 16 amp solid state regulated stator. Which is round, and is somewhere, not illustrated in the manual. Which is also not the magneto. Which I can't find in the manual. All of which I'm sidetracked on in an effort to understand the schematic above. Which I'm not succeeding in.

So for the moment, the tractor is drivable, using the ahem, "manual" kill wire engagement feature. I'm not quite sure where to turn next, but I am grateful for your help.

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PhanDad

Think of the electric flow as water flow; water flows from high to low. So the current flows from the 12v+ terminal to the negative terminal (which is ground) of the battery. Along the way it does work. In the following diagram I've traced the starting cranking wiring in red and the kill wiring in blue:

16GTHL_Wire7116c.jpg

For the start/crank wiring, the 12v+ starts at the ignition switch, and if a ground is present, it will flow. It first goes to the solenoid and will flow though the solenoid "pull in" coil if there's a ground on the other side of the coil windings. If the 3 safety switches are satisfied, there is a path to ground and the current will flow and the engine will crank. (In case your not familiar with electrical symbols, the striped arrow head symbol (pointing down) just above the "W" in "switch", is the ground symbol).For the "kill" wiring, the current (from the voltage produced by the magnets and magneto) needs to flow through the magneto coil to produce a spark. If there's an easier path for the current to go rather than through the coil there will be no spark. (Water at a dam has to build up before it can go down - if there's a hole at the bottom it'll go there before going over the top) The "kill" wire is the "hole in the bottom". The kill wire is connected to the "upstream" side of the magneto coil (not shown in the wiring diagram, it's internal to the magneto). When you turn the ignition switch off, there is a path to ground as shown by the blue line. If the IM is wired in, then there's a path to ground through it shown by the dashed blue line. If any of the wiring insulation is rubbed off and touching the frame, etc (ground), the circuits don't work as intended. Since the start circuit is what I call "powered" (connected directly to the battery) and has the potential to carry high current, a wire rub is easy to find on the upstream side of the solenoid since usually smoke, sparks, and/or fire happen in addition to the engine not cranking (the circuit breaker should minimize the damage). The "kill" wire is a low power circuit, a wire rub doesn't usually involve any smoke, etc and therefore is much harder to find.What I have described above is how basic electrical circuits were taught to me; hopefully it makes an "ah ha" moment for you and is not meant to insult anyone's intelligence. Now just for confusion, the current (electrons) actually flow from the negative terminal to the positive terminal but we won't go there.

16GTHL_Wire7116c.jpg.e07ef2749a79e572acd139f1f7276cb8.jpg

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PhanDad

Also, the 1919 to 1981 Briggs manual doesn't show the breakerless magnetron ignition (at least not that I could ever find). In section 2, page 23, figure 74 and page 25, figure 77 are the best I can find of the "magneto".

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theniteowl

These electrical diagrams are very basic and can be confusing if you are not used to reading them or when they carry components that have internal operations that result in different outputs under different circumstances.

For this issue it might be easier for you to think only of the line that grounds out the ignition to keep it from getting spark.

All of those safety switches are not all ganged together like in the diagram with only one wire to them, they are all separate possible ground paths for the one wire.

Think of this as a single wire with a number of connections that have the possibility of connecting that wire to ground. List out all of the possible normal ground connections then check them one by one.

Your key switch should only provide a ground when it is in the OFF position. As PhanDad suggested above, disconnect your battery. You are best off disconnecting the negative cable then you can have no shorts while testing.

Your multimeter probably has an audible continuity test setting which is the easiest to use for this purpose as you do not have to watch it, only listen for the tone when a connection is made.

First test would be the disconnected end of your kill wire. Connect one probe to that wire making sure they do not touch the frame of the tractor or any other wires then touch the other probe to some clean spot on the frame of the tractor or the engine. If it beeps then the small voltage from the meter is traveling down that wire and somewhere being connected to the frame of the tractor.

You should get a beep when the ignition switch is turned off because the switch is connecting that wire to the frame via another wire on the switch. Turning the ignition switch to the on position should disconnect that ground path. If it does not then there is a ground connection somewhere else on the wire or the ignition switch is shorting that pin to ground.

Next step would be to check which pin on the ignition switch connects to ground and if you disconnect that ground wire does the test on the kill wire to the chassis still cause a tone from the meter?

Perhaps an easier way to envision this is that each switch is connected permanently to ground on one side and to the kill wire on the other side. If you remove the ground to the frame at each switch you should eliminate the ground to the kill wire. If all switch grounds are disconnected but the kill wire is still grounded then the wire jacket has been rubbed off somewhere and the wire is connecting directly to the frame and you would have to trace the wire physically to find where it is happening.

If after disconnecting all the switch grounds you do not have a ground on the kill wire then you can reconnect the switch grounds one by one to see when it comes back. Remember of course that the switch needs to in it's safe position for the test to be good. For instance if the seat switch were connected you would have to sit on the seat or at least push on the part of the switch that would cause it to disconnect the ground internally. The normal state of that switch is called normally closed which means it is closing the connections between the input and output wires so they become a complete circuit.

Some switches are normally open and have to be pushed down in order to make that connection.

Eliminate the possible grounds one by one, it is the simplest way.

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PhanDad

theniteowl,

I dislike the he's right, she's right type of discussions/posts.

But your statement "All of those safety switches are not all ganged together like in the diagram with only one wire to them, they are all separate possible ground paths for the one wire."

They are wired as shown in the diagram; there are 2 wires to each safety switch. The switches "make" when sasified (terminals connected together), they do not go directly to ground via either terminal or through their case. They are wired in series so that if any switch is not satisfied, there is no ground connection for the solenoid and the engine will not crank.

If they were wired as you suggest (each independently grounded), then if ANY of the 3 safety switches was satisfied, the solenoid would close and the engine would crank.

The safety switches are not wired directly to the magneto "kill" wire. There are only 3 items connected to it as shown in the wiring diagram: the ignition switch, the IM, and the magneto. The IM also interfaces with the safety switchs as shown in the diagram. The IM's job is to kill the engine if the operator leaves the seat with the PTO engaged or the transmission not in neutral. It does this by grounding the "kill" wire as shown in the diagram.

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JohnFornaro

Well. A busy afternoon yesterday, using the uhhhh.... manual kill switch. Tractor starts and runs with kill wire disconnected. Turning the key "off", but not grounding the kill wire will not stop the tractor. For "safety's" sake, you have to turn off the key, then ground the kill wire. Here's the wood crib:

Wood-Crib-11-14-15-lo-rez.JPG

And here's the 20" dead oak which was miraculously transformed into firewood:

Wood-Pile-West-Elevation-11-14-15.JPG

Couple of comments. 1. I also have the Briggs, "Single Cylinder 'L' Head Repair Manual" (Built after 1981) In the Ignition section, they discuss the Magnetron ignition, whereas in the 1919-1981 manual, they call it Magnevac. (Mild rant: Changing the name is SO innovative; must be better, eh?) Anyhow, section 7c, Fig. 12 seems to show the charging system that I have. (A bit more of a rant: The manual assumes a broad previous knowledge from the reader, and thus skips the context for a great many of the subsystems which comprise the engine. Never is the stator, armature, magnet, flywheel, Magnetron, whatever, shown in an assembly drawing. If I had the money to retire, I would re-write the manual along the literary lines of, and in the artistic style of, my "Motor's Auto Repair Manual" of 1952.(No, the File, Motor's-Ignition-p-9-1952.JPG was NOT uploaded to the Server. Even at 67K file size. Friggin' computers.)2. Note that (if I can get it to upload) the Motor's schematic shows both positive & negative "wires". The Starter circuit is shown in a different diagram, also easy to read.3. I do have familiarity with basic electronic schematic symbology, from my days working on the railroad in the mid to late 60's. The railroad being Lionel, but hey. We learned about basic electricity in school, when the politically correct viewpoint was that school was for learning, not social programming. I thought you were supposed to learn things like basic electricity for life, so I did. Hmmmph.4. Still, I'm struggling with the schematic for a bit more, plus I have work to do, and I have a hard time tearing the tractor apart to track down this problem, but I will.5. OK. five comments. Many thanks, guys.

Wood-Crib-11-14-15-lo-rez.JPG.b2e07465095224294ebff68a3d00183e.JPG

Wood-Pile-West-Elevation-11-14-15.JPG.f52ef782e0f80e4c33c1e52887640eeb.JPG

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