LT1018 not starting, just turns and turns

[dinosaur12]

Background:
I have a LT1018 with about 150hour on it running the 18.5hp BS engine. Last time I used it the unit seemed to have a strange vibration to it. Shut it down and checked the blades but nothing looked out of place. Finished with the yard work and shut it down. About 30mins latter tried to start it up and it would just turn and turn but not start. Pushed it in the garage and called it a night.

The current problem:
Right now the batt is dead so I am jumping it from my truck batt. The engine turns freely but does not start. Took spark plug out and with it connected to the coil can see it sparking when trying to start, so I know its getting spark. I then took the carburetor off and sprayed some carb cleaner in the intake and tried to start again. It made some backfire noise but nothing significant.
I pulled the fuel line from the carb and it is defiantly getting fuel to the carb (aka, fuel pump is working). I am not 100% sure if it is getting fuel from the carb to the intake. When I took the spark plug out again it was wet so I am pretty sure it is getting fuel but not 100%.
I took the valve cover off and had the starter turn the engine and could see them both moving up and down. Tried to do a compression test on it but got nothing. The gauge I have is for automotive so I'm not really sure it would pickup the compression from the BS engine.

I am hitting a wall with this. It has spark, has oxygen, and I'm pretty sure it has fuel but does not run. I am guessing I am missing something but not sure. I am hoping one of you guys/gals knows of a switch or something that might cause this problem.

Thanks for any help.

[Sam Mac]

Originally Posted by dinosaur12

Background:
I have a LT1018 with about 150hour on it running the 18.5hp BS engine. Last time I used it the unit seemed to have a strange vibration to it. Shut it down and checked the blades but nothing looked out of place. Finished with the yard work and shut it down. About 30mins latter tried to start it up and it would just turn and turn but not start. Pushed it in the garage and called it a night.

The current problem:
Right now the batt is dead so I am jumping it from my truck batt. The engine turns freely but does not start. Took spark plug out and with it connected to the coil can see it sparking when trying to start, so I know its getting spark. I then took the carburetor off and sprayed some carb cleaner in the intake and tried to start again. It made some backfire noise but nothing significant.
I pulled the fuel line from the carb and it is defiantly getting fuel to the carb (aka, fuel pump is working). I am not 100% sure if it is getting fuel from the carb to the intake. When I took the spark plug out again it was wet so I am pretty sure it is getting fuel but not 100%.
I took the valve cover off and had the starter turn the engine and could see them both moving up and down. Tried to do a compression test on it but got nothing. The gauge I have is for automotive so I'm not really sure it would pickup the compression from the BS engine.

I am hitting a wall with this. It has spark, has oxygen, and I'm pretty sure it has fuel but does not run. I am guessing I am missing something but not sure. I am hoping one of you guys/gals knows of a switch or something that might cause this problem.

Thanks for any help.

Automotive compression tester is just fine, sounds like you have a compression issue.

[dinosaur12]

Originally Posted by Sam Mac

Automotive compression tester is just fine, sounds like you have a compression issue.

Thanks for the quick reply.

I would agree with the above statement. But...for my knowledge what would you suggest if I had not done the compression or lets just say it came back fine.

[Sam Mac]

You said you checked the compression and got nothing, if that is the case something inside is broken. Valves, rod, piston. You need to dig a little deeper. You may want to post in the engine section.

[Vince_o]

STOP!

Reset the exaust valve to .06 and intake to .04 and it will run like a top.

If you still get backfire, your cam is shot. We do about 5 of these a month, commen problem with a briggs.

Just trying to help!

[dinosaur12]

Originally Posted by Vince_o

STOP!

Reset the exaust valve to .06 and intake to .04 and it will run like a top.

If you still get backfire, your cam is shot. We do about 5 of these a month, commen problem with a briggs.

Just trying to help!

Thanks for this info. I ran out and had a look at the valve play and the exhaust (upper) was WAY out. I could almost stick my finger between the valve/rocker. The intake (lower) was much closer.
Still getting no compression and engine is still turning. I am having a mobile repair guy come out tomorrow and have a look. Am hoping my compression gauge is broken and its something stupid simple that I am missing.

On a side note. What are our guys thoughts on my situation? Should I get a new/rebuilt motor and drop it in (any tips on where to get one)? Rebuild the current motor? Look to buy a "new to me" mower (any brands/models I should avoid or keep an eye out for).
The grass is getting pretty tall and Im sure the neighbors are loving me right now.

Thanks for your guys input.

[Vince_o]

YOu could short block it.

The thing about the compression test is, it just tells you if you have compression. If you could have a leak down test done, this would tell you if you have a valve train, ring, head problem.

If your unit was on my bench, I would have tested for spark, a plug can fire outside the head, and not fire under compression. I have a tester for checking the secondary windings in the coil. A coil can fire from the primary winding and not the second. Then chacked for fuel. Checked the valves, then if it wouldnt start, do a leak down test. Briggs cams are soft all engs for the most part have some type of comp relese on them. Even big chainsaws have compression release buttons on them.

Im not a big fan of briggs, notice I said briggs, not vanguard, theres a differance. If the mower is in good shape Id replace it or short block it. I do alot of short blocks with briggs. When you do it just be sure to put all new filters on it, cause it basicly is a new eng. I dont know what they cost, I dont see prices but I get paid 2 hours to do one.

If it has an elec pto be sure it goes back on right, theres a 300 mistake, ask me how I know. And youll more than likly have to put a new drive pully on, most times they are rusted to the crank. Heck your there do a drive belt too and check the idlers, espically that lone one by your left foot.

Let us know what they find.

[dinosaur12]

Its the exhaust valve. Finally got to do a leak down test and the upper valve was leaking no matter what I did.

What I am now thinking about doing is buying a used mower so I get the yard cut and keep the neighbors at bay. Then pulling the head and fixing the valve and then sell the Cub (or keep it and sell other mower). Looks like I can get the whole head for about $125..........Thinking about it.

Thanks all for the help.

[Vince_o]

Chances are its just some carbon under the seat. You can pop it out and use a small brass brush in a die grinder clean it all up and pop it back in youll be fine.

How was the rings on the leak down? Much blow by?

I got to thinking last night, if theres no compression, and that rocker was out as far as you say, it wouldnt turn over.

[dinosaur12]

Originally Posted by Vince_o

Chances are its just some carbon under the seat. You can pop it out and use a small brass brush in a die grinder clean it all up and pop it back in youll be fine.

How was the rings on the leak down? Much blow by?

I got to thinking last night, if theres no compression, and that rocker was out as far as you say, it wouldnt turn over.

It was a friend who came over and had the pressure tool. Never used one but I am pretty sure it was saying 100% blow by. Meaning it was not building any pressure at all in the cylinder. Again, not really sure this info is accurate but am thinking its right. I was pushing on the valve, trying to spin the valve, and tapping it lightly with a rubber malate to see if it would knock some carbon off but it did not seem to change anything.

I am going to try and get some time to pull the head today and will try to post some pics. Should be fun!
Never disassembled a engine this far. Have done most repairs outside the engine but never gone inside. This is going to be a good time for me to really jack it up good