Briggs Engine Will Not Start

[mtnlovrs]

briggs doesn't publish compression specs for their engine. I like to see 90 or above on most engines, but have seen new briggs engines on push mowers run fine with 55-60 psi.

Hopefully, loose head bolts were the problem. I will find out tomorrow when I get it back together. If it still doesn't start, then I will know this mower is simply possessed!:confused2:

 

[Boobala]

Hopefully, loose head bolts were the problem. I will find out tomorrow when I get it back together. If it still doesn't start, then I will know this mower is simply possessed!:confused2:

My wife says you probably have "the-pixies" problem ......... she has the "calories-problem" ..... you know , those things that go into your closets at night .... and magically make ALL your clothes fit TIGHTER !!
She said sometimes if you put a BIG hammer and BIG screwdriver in front of it ... it gets so scared .... it fixes itself ! I don't need Encyclopedias ......my wife knows it all !! Boobala :laughing: :laughing:

 

[reynoldston]

An internal combustion engine requires 3 things to run :

1. Fuel .... ( you obviously have that covered ) ( vented gas cap ?? fuel shut-off open ?? )

2 Air .... Thats a given ... provided the air cleaner / filter is NOT restricted

3 Fire .... Spark is where I'd look ( sometimes when a coil is about to " go on extended vacation " it'll work itermittently )

PLEASE keep us informed ........ its kickin my "set- down" along with yours !!! BEST of Luck, I hope SOMEONE can find the solution !!! Boobala :confused2: :confused2:

Don't forget timing

 

[mtnlovrs]

Don't forget timing

Crankcase has never been opened and everything is moving as it is supposed to, therefore, I don't believe the mechanical timing could have been changed. I replaced the flywheel key and have gone back to make sure it hasn't sheared again... so that takes care of the ignition timing. Thanks again. I'm heading out now to get it back together. I'm a second shifter, so I don't get going very early in the morning.

 

[mtnlovrs]

My wife says you probably have "the-pixies" problem ......... she has the "calories-problem" ..... you know , those things that go into your closets at night .... and magically make ALL your clothes fit TIGHTER !!
She said sometimes if you put a BIG hammer and BIG screwdriver in front of it ... it gets so scared .... it fixes itself ! I don't need Encyclopedias ......my wife knows it all !! Boobala :laughing: :laughing:

Thank your wife for me! I don't need an encyclopedia either because my wife has been to the end of the Internet and back several times now. Tell your wife I will include those tools in my arsenal when I head back out there today!!!:thumbsup::laughing:

 

[reynoldston]

Recheck your work, you missed something. Spark, fuel, compression, timing. You are missing one of these or it will run. How are you making your test? You are checking your spark under compression right? Checking compression with a gauge or a leak down test ? Installed flywheel with proper torque? Give carburetor a really good cleaning? Just stop and think what you are missing?

 

[Boobala]

At the risk of looking like an ignorant fool ..... by all accounts this engine should be running, I mentioned in another forum or thread ...... one last thing I finally remembered from a Loooong time ago ......... a guy told me he had a similar issue ..... drove him crazy , forget why .... but he removed the muffler and it fired up..... found his muffler was clogged with carbon !! at this stage of the game , MAYBE , it's worth a look-see ?? I really really want to know what the problem is ( I'm sure some others following this thread would also )
I really was thinkin the coil , but ............ Boobala :confused2: :confused2:

 

[pugaltitude]

Briggs & Stratton Model Number: 123K02-0258-E1 03012456
Craftsman 6.5 HP Self Propelled Mower Model Number: 917.377660
I have tried absolutely everything to get this mower started, and it will not start. This mower belongs to my mom and hasn't ran in two to three years. I knew the carb would be varnished and gummed up. I performed the following before attempting to start the engine:
1. I cleaned and rebuilt the carburetor, including cleaning all the ports and blowing them out with air; replaced the welch plug; the float needle and seat; the float bowl gasket and the air filter housing gasket; fuel hose; and tested the float seat by both blowing and sucking on the fuel inlet nipple to make sure it was seating. Please note, this carburetor does not have any adjustment possible... no fuel mixture or idle screws... no choke... the only moving part is a throttle plate.
2. I cleaned the mower and engine thoroughly from top to bottom, inside and out.
3. Changed the engine oil.
4. Removed and cleaned the gas tank, inside and out. I blew it out with compressed air and made certain it was clean.
5. Found the flywheel key sheared; removed, cleaned and replaced with new aluminum key.
6. Set the coil air gap to .006" (Spec is 6 - 10 thousandths).
7. Replaced the spark plug (three times). Checked the coil lead for cracks or damage. Checked and cleaned the kill switch wiring and switch.
8. Checked the cylinder compression and found it to be at 55 psi and holding.
9. Replaced the air filter and primer bulb.
10. I checked the spark and had a nice blue spark.
11. Filled the tank with fresh premium gasoline.

I tried starting it with starting fluid, carburetor cleaner, and WD40 with no luck. Then, I finally managed to get it running once by squirting brake cleaner in the spark plug hole and it ran perfect. After shutting it off, it wouldn't start again even with the brake cleaner. I tried squirting the fluids in both the carb and the spark plug hole. I tried using a known good spark plug out of another mower and three other brand new plugs with no luck. Finally, one more time it started, but only for a few seconds and then it quit again, not to be re-started. I pull and pull on the rope to start the engine, and it doesn't even seem like it's trying. I am so frustrated with this thing I can hardly stand it. I am a mechanic by trade and can't believe this this is kicking my butt! I am desperate for an answer... please help.

You really do need a spark tester when checking for spark.
A blue spark means nothing. It could be pink with an aluminous yellow dress on it would make no difference.

I would expect that the metal suppressor cap on the end of the spark lead ay be causing your issue.

The easiest way to set the coil to flywheel is with a business card.
Also the date code of the engine depends on what spark plug to be fitted.

Is fuel being push up the main jet when primer bulb being used?
Remove the air filter cover and look in the carb. Fuel should be squirting up.

 

[reynoldston]

At the risk of looking like an ignorant fool ..... by all accounts this engine should be running, I mentioned in another forum or thread ...... one last thing I finally remembered from a Loooong time ago ......... a guy told me he had a similar issue ..... drove him crazy , forget why .... but he removed the muffler and it fired up..... found his muffler was clogged with carbon !! at this stage of the game , MAYBE , it's worth a look-see ?? I really really want to know what the problem is ( I'm sure some others following this thread would also )
I really was thinkin the coil , but ............ Boobala :confused2: :confused2:

I find as a rule a plugged muffler you lose high speed unless maybe nothing go's through it. This is what I have found when I come across a plugged muffler.

 

[mtnlovrs]

Recheck your work, you missed something. Spark, fuel, compression, timing. You are missing one of these or it will run. How are you making your test? You are checking your spark under compression right? Checking compression with a gauge or a leak down test ? Installed flywheel with proper torque? Give carburetor a really good cleaning? Just stop and think what you are missing?

Believe me, I have done that many times and I have double, triple, and in some cases quadruple checked my work before ever coming to the forum. I know this defies all logic. That's why I came here asking for help. As I mentioned earlier in this thread, My wife helped me check for spark. I do not have a spark checker. First, I pulled the rope while she held the sparkplug against a head bolt. Then, we swapped places so that we both could see the spark with our own eyes. The spark was a thin blue spark. The carburetor could not be cleaner. I have taken it apart now four or five times. I used the correct drill bit sizes to clean every orifice, thoroughly cleaned all surfaces inside and out with carburetor cleaner, and blew out all the orifices with compressed air, making sure that air was coming out the other end of each orifice. I replaced the float needle and seat. I pressed the seat (ribbed side down) all the way down into the recess with a 3/16" drill bit and made sure it was flat in the bottom of the bore. I checked the float and seat to make sure it was seating by blowing and sucking air through the fuel inlet. The float is hanging horizontally to the carb body, as it should. I replaced the welch plug and seated it in place using a 1/4" extension because the rounded end of the extension fit the plug perfectly. I replaced the gasket, O-ring, air filter and primer bulb. There are no adjustments possible on this carburetor - no idle or mixture screw, no choke. When I checked compression, I used a cylinder compression tester. I now realize that the next step is a leak-down test. Yesterday, I checked the flywheel key again (not sheared). I found an incorrect torque of 138-150 foot pounds in an old book, so I torqued the nut to 110 foot pounds because that seemed too much for this engine. I have since found the correct torque for the flywheel on this engine: 55 foot pounds. Next, I replaced the intake manifold tube gasket, removed the head and cleaned out all of the carbon. I checked the cylinder bore and did not see any signs of scoring or damage, but it was pretty oily. I checked the valves to see if they seated snuggly during the compression stroke, and they were nice and tight. There was no sign of any damage to the valves or their seats. I cleaned everything and re-torqued the head to 140" lbs. I used copper spay-on head gasket sealant on both sides of the gasket. Today, I tried starting it again and, unfortunately, still the same story. Once again everyone, thanks for all the help. Please keep the ideas coming... there must be a reason this simple little motor won't start.:thumbsup: