I'd be a bit curious on HOW you checked for spark.
Did you use a tester?

You may get an external spark with the plug out or grounding the lead to the block, but that's no guarantee that you have spark at the plug under compression.

"checked carb to see if fuel was reaching it but it wasn't."
"pulled fuel line at carb and cranked engine, still no fuel coming to carb. "

How would you expect this to show anything since the fuel pump is built right into the carb, no line from fuel pump to carb. You are checking the correct line? The fuel line connects on the side of the fuel pump and the vacuum line from the engine block connects to the bottom of the fuel pump.

" Took off gas cap and blew pressure into the line and as soon as fuel got past the filter it starts to siphon back to the tank."

Sounds more like you have lines connected incorrectly.

Walt Conner

@ Walt -I Know exactly what line is which and they are connected correctly...if it was drawing fuel it would be at the fuel pump then to the carb. It isn't making it to there.

*Just my thought but I first need to be able to get it to fire because if it isn't firing it seems that I won't have any fuel flow.

. @ Bill no I didn't use a tester and yes I did ground it against the chassis and got a good spark...never considered that it may not react the same way under pressure in the cylinder.
So that being said and I'm aware the magneto is responsible for my spark, is there a way to test the magneto to know if it is putting out the proper amount of current? An ohm meter perhaps? I wouldn't have a clue as what the correct reading would be.
* I should mention that a few years ago I had a similar issue and I replaced the magneto but with a used one off another mower... so I suppose it could have failed.

If these Opp Twins have an Achilles heel, it is their Magnetron ignition.
I don't think you fully appreciate what Walt was saying about fuel flow in his post.
Unless this version is one of the minority with a separate fuel pump, when the fuel hose is DISCONNECTED FROM the fuel pump on the carb, no matter how much you crank the engine, there will not be any fuel flow, because the pump is no longer part of the picture.
On the Opp Twins you pretty much have to remove the top of the carb to see if fuel is filling the bowl.....or not.
Because the main jet is deep in a well at the bottom of the carb, it is sometimes the case that a rather large bit of debris can find its way to the jet and block it suddenly.

This post was edited by mownie on Sat, Sep 7, 13 at 13:39

Thanks Mownie I get what you Walt are saying with a hose disconnected (like the vac hose under the pump) it wouldn't get fuel flowing because no vacuum exists to make the pump work.
Anyway I think I may have not been totally clear as to what I did and what I was checking for. Nor did I explain that the mower had been running fine and the morning this happened it had been running fine for about 3 min. when it sputtered and quit running. So I first looked to see if it had ran out of gas (no) and I looked down to the fuel filter to see if it may be clogged with some debris and noticed that the fuel was siphoning back to the tank. This is what made me initially believe I had a problem with the fuel pump and bought and installed a new diaphragm kit. Neither the fuel or vac lines are cracked or have an air leak, the vent hole on the tank isn't clogged, fuel filter isn't blocked, Took apart the carb sprayed out all the jets, float and needle seem to function properly, reassembled and reinstalled then tried to start and obviously it didn't lol.
Now the one thing I didn't do is remove the main jet at the bottom because I was able to shoot cleaner through it so I was pretty sure it was clogged up.
But it still brings me back to why won't this thing fire even when I primed the bowl or shot gas directly into the cylinder ...at this point I am leaning to Bill's suggestion that my spark may not be enough to get a good fire and that would lead me to believe I have a magneto issue. I'll see if I can find out what the ohm reading should be and or another way to test the magneto.

Hey I just wanted to say thanks so much to you all for your help so far you guys have a lot of knowledge and a poop load of patience to boot!
-Jon

Well, you have pretty much eliminated all the "fuel sided" aspects of the equation.
The only sure way to check the Magnetron ignition is to use the Briggs ignition tester (Briggs part # 19368) and follow the instructions given by Briggs for it's use.
This low cost tester takes into account the effects of compression and gives a real representation of what is taking place while the engine is cranking or running.
One reason Briggs does not provide electrical specs (Ohms and such) for the Magnetron units is that there are actually some electronic components inside the unit (it ain't just a couple of coils) which affect the operation.............and these components cannot be separated from the rest of the circuits for any external tests.
So, basically the only good test is to check for spark using the Briggs spark tester.............or a known good, spare Magnetron unit.

Thanks! I'll be getting a Briggs tester and post back in a couple days with my results.
Have a great Sunday folks!

Hi everyone just an update...well a year later I'm back at this beast and here is what I found out over the last 2 days...spark (when grounded against engine body) is there and then it's not. I actually cranked it off and on for several minutes and now get NO spark at all. I did a multimeter test on the spark plug wires to the magneto and get a reading of 1 ohm even when cranking, ohm reading does not change whether key on or off cranking or not. Tried once again to get some spark by grounding against the body and still nothing. I'm really leaning toward a bad magneto but wonder what you all think on this.
I also have since replaced fuel pump body and diaphragm and totally cleaned carb (twice) and what I have noticed is when I crank the engine fuel spews out from the front of the fuel pump and my guess is that because I have little or no spark to ignite the fuel it just keeps pumping and thus overfilling the bowl and out the front. I did not however replace the float needle as it was new 2 years ago and shows no sign of being wore down.
I would sure appreciate your ideas and suggestions whether this seems plausible.
Thanks again fellas for all your help...hope to get this straightened out over the next few days and post some good news when it is! Cheers

I should have added that I have not yet purchased a Briggs spark tester...have been spending mega bucks on fixing my Zero turn nightmare, but I'll save that for another thread LOL.

"Thanks! I'll be getting a Briggs tester and post back in a couple days with my results. "

You could have waited 3 more days and been a full year!

So apparently you didn't get the tester?

3 things I can thing of-
1. Bad magneto.
2. Grounded kill wire.
3. Magneto not grounded to engine because of rust.

You can use your Ohm meter (if it still works after trying to send thousands of volts to it in a non voltage position) to check if the wire is grounded. Possibly you have a safety switch issue?

You might also post the Sears 917.xxxxxx number so one can look up the proper schematic.
There are at least 20 different Craftsman tractors that use that identical engine. Maybe more?

This post was edited by bill_kapaun on Fri, Sep 5, 14 at 12:54

Hey there Bill!
I disconnected the small black wire to the magneto (which I assume goes to the kill switch) to see if that was the problem but no difference and also unplugged the seat switch to see if that may be it but still nothing.
I noticed when I had spark when checking this AM it seemed quite weak, spark was blue but barely visible and then it just stopped sparking all together. Did a check with another spark plug I had that is known to be good and still got nothing leading me to believe it's probably not the plugs.
The engine I'm speaking of is a Briggs 42E707 twin cyl.
sorry I didn't post that to begin with. :)
Good thing I didn't fry my MM when I cranked it...another clue that my issue may be the magneto

You posted the engine model in the title.

Without a schematic to look at, one can't tell if unplugging the seat switch is the proper thing to do. Sometimes, that INSURES you won't have a spark.
Without a Sears 917.xxxxxx, one can't be sure if they have the correct schematic.
I've seen one case where virtually identical tractors, 1 model number apart had 3 Operator Presence Relays and the other had none.

That engine was used over a span of 4-5 years that I know of back in the era when they were changing safety switch systems seemingly every month, trying to stay a step ahead of those trying to defeat them.

Bill It is Craftsman model 917.270821

My apologies for not including all the correct info in my OP...I sure make things hard sometimes! LOL

Since you have no/marginal spark with the kill wire disconnected to the magneto it's either-

Bad Magneto
OR
Bad Magneto ground

Since you have to remove the magneto to change it, you might try cleaning the ground connection and reinstalling it.
IF the problem persists, you need a new magneto.

BTW- Unplugging your seat switch WILL kill spark.
The connector has a shorting tab in it that completes the circuit when unplugged.

Thank you so much Bill for your help! I wasn't quite sure about the seat switch but it appears to be a non issue as I had some spark prior to the plug/unplug.
I'm going to recheck my magneto ground before heading to the parts store tomorrow ($58.00 they quoted me)
I'll let you know how it works out :)
Cheers!

Well after more troubleshooting than I ever care to do again I am happy to say this little beast is finally running. Installed the new magnetron coil and still couldn't get it to run, just backfiring through the carb like it has been. Since timing is controlled by the flywheel key I checked that and it wasn't sheared so what could it be???!!! Later that evening while sitting by the campfire with my gearhead friends I threw the scenario out and after a few minutes of Q and A my friend says " I had a similar issue once and after doing all the usual tests (spark fuel air) I decided to pull the head and when I did I found a screw blocking the intake vale from closing all the way".
Well as soon as he says 'screw in the intake' I had this Ah ha moment...while looking at my air cleaner parts that day I noticed I was missing two of the three screw bolts that holds the air cleaner down. So today I pull one of the heads and BEHOLD I find my missing screw wedged in between the intake valve keeping it from shutting all the way...pulled the other head and guess where I found the other? Yep wedged in the other valve.
So screw bolts are returned to their proper places (except for one which was pretty chewed up, will replace with new tomorrow) filled with gas and started on the first try and is running like a champ!
I want to thank Bill and everyone who offered their assistance to me, as miserably long as this was to figure out I finally did and in the end I enjoyed the process as I gained some needed knowledge and patience. I will also make damn sure in the future to never start an engine with loose parts near an intake! It was something I had done a thousand times before and never had a mishap but hard lessons are ones I won't forget.
Thanks again amigos...now it's time for some good beer!!!
Cheers -Jon