18 H.P briggs and stratton engine ? dead cylinder help please

newfee_bullettAugust 27, 2007

Hi guys first post here I've been trying to figure out what's up with one of the 2 cylinders on the 18 hp briggs and stratton engine I have..it's a twin cylinder model number is 422447. I've noticed a serious lack of power when under load to the poin that it's stalling out...I have it narrowed down to what I think to be a dead cylinder. I tried the pull a plug wire while it's running to see if it still runs and while the one side will keep running with a slight drop in rpms the other side kills the engine. I've checked the plugs they are fine, and I have fire comming from the possible dead side. I've looked at the valves to be sure that they were moving and that seems to be fine but I'm not sure how to check the clearences. I did take the valve cover off to check the valves movement and when I put it back on and fired it up it seemed to be fixed for about 30 secs then I'm back to where I was. Right now I have the carb off and was toying with the adjustable or "non adjustable jet as it's called" thinking that might help but either I wasn't getting the right setting or it's not the problem. Any tips or links to break down diagrams would be greatly appreciated.


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canguy(British Columbia)

Switch the plugs from side to side. If the same cylinder acts up, then the problem could be the coil or a bad high tension wire. An in line neon spark tester could help here. I have also seen that engine series swallow a throttle plate screw that gets lodged in the intake valve.

    Bookmark   August 28, 2007 at 12:07AM
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That appears to probably be an older engine?
What's the type & code#'s, since there are 2 different IPL's for that model#.
You can download an IPL from the Briggs site that MIGHT be somewhat useful for the carb. See Link.
Do you have a compression tester to compare the 2 cylinders?

Here is a link that might be useful: Link

    Bookmark   August 28, 2007 at 3:52AM
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""non adjustable jet as it's called" thinking that might help but either I wasn't getting the right setting or it's not the problem"

Not the problem. As Bill says, check the compression if possible. I would suspect a valve seat has come loose. Check the valve clearance where you were checking the valve action. Turn engine to TDC plus 1/4" down from top after TDC. Use flat feeler gage between the tappet and valve stem. Clearance .004" to .006" for Intake .007" to .009" for Exhaust.

Another horrible thought, it may have thrown a rod on that cylinder. Remove the spark plug for that cylinder, remove the other plug wire so it won't start, hold you finger over plug hole and run starter. If it doesn't blow your finger off the plug hole, you need to pull the head and you will easily be able to tell if piston if moving, valve seat is out or a screw has wedged under valve.

Check that Intake Manifold is not leaking where it attaches to the cylinder block for that cylinder, spray WD-40 at the connection.

Ignition coil for that engine fires to both cylinders at the same time from one single coil so unlikely that is the problem.

Walt Conner

    Bookmark   August 28, 2007 at 8:00AM
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Thanks guys, to answer everyone....Canguy checked the plug wires there's fire from both ends and from what I could see there's nothing lodged in the intake but I'll take an even closer look.
Bill: the type and code for that engine is TYPE 1156 01 CODE 88091512 I don't have a compression tester (yet) but to answer some of
WALTS: ideas I tried the finger over the hole test and yeah it blows my finger off the hole...I checked to make sure that the rods and valves are moving thinking that mayby it might have been stuck but everything appears to be moving fine. I'm thinking that the valves clearences might be where I'm heading but I've got 0 experience with dealing with valves and compression (but there's gotta be a first right) so if someone doesn't mind being as detailed as they can for how to go about the checking and fixing that would be awesome. I'm unsure what you mean by "TDC" and when you say 1/4 past it, is that 1/4 turn of the flywheel? If it's too complecated or too much to write in here no worries the help you've given so far as been amazing.

    Bookmark   August 28, 2007 at 10:09AM
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well I've been out tinkering with the engine again and I'm at a loss...I put the carb back on but cleaned it up a little before doing it just to see what would happen before I dove into the valves and clearances, I cleaned the plugs up fired it up and for about 10secs the dead cylinder was holding. it's back to being dead again now....I didn't think that if it was in the valves it would correct itself for 10 secs or so would it?

    Bookmark   August 28, 2007 at 1:10PM
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ok here's an update. since my last post I've been toying with the carb quite a bit and have somehow mangaged to bring life to the dead cylinder. it's not as strong as the original good one but it does run when the wire for the "good" cylinder is pulled. it seems to systematically shut itself down though. meaning I pull the wire and you notice a sudden drop in rpms then after a good 2-3 secs there's another drop then another. it will hold at one of the levels but ocasionally it continues it's drops until it stalls. The "good" cylinder however has a very slight drop in rpms when I pull the wire from the "dead" side. I do notice a fair amount of carbon discharging from the "dead" cylinders exhaust side and the plug is getting fouled up when running with both wires attached and while pulling the wire from the "good" cylinder. I'm new to the whole engine repair world but I'm thinking that I'm back to looking at the valves am I to further correct the problem or is there something else?

    Bookmark   August 28, 2007 at 2:28PM
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The 1/4" down past TDC is the piston 1/4" down from the top of cylinder past TDC. Not quite sure how you check that on your engine since the spark plugs go in at an angle. I guess you find TDC then turn the flywheel just a LITTLE more clockwise.

Did you check for leaks where Intake Manifold bolts up? Also, that is an old engine. Does it have a two pc. aluminum Intake Manifold riveted together at a seam? Some times these leaked.

As for cleaning carbon AND the carb out, some SeaFoam in the gastank does a good job with that but not sure you want to run the engine basically on one cylinder that long.

Still think it COULD be a valve seat.

Changing the valve clearance on that engine is not real easy and too long to try to tell here. Maybe Bill will tell you if not,

wconner5 at verizon dot net

Walt Conner

    Bookmark   August 28, 2007 at 3:50PM
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TDC is when the piston is at the top of the stroke and firing. Both valves will be closed on THAT cylinder.
1/4" past means the piston moves 1/4" down from that point.

Get yourself a set of feeler gauges.

TO START, use the smallest gauge for that respective valve-
.004" to check the intake
.007" to check the exhaust
This is a rough test here, but should be sufficient-
Set piston to TDC- One cylinder will have both valves closed and one won't.
See if respective gauge will slide in the clearance between the valve end and the lifter. If it doesn't, rotate the engine VERY SLIGHTLY and repeat. Check both valves.

The main thing is that you have enough clearance to slide the smaller gauge in without having to force it.

You might use a wooden pencil to use as a "make do depth gauge". You should be able to tell when the piston is at the top of the stroke, and when it starts to move.

BTW, a spark plug can "APPEAR" to be fine, but fail when under compression. Stick in a couple new ones, properly gapped. It's TOO inexpensive NOT to.

    Bookmark   August 28, 2007 at 5:22PM
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ok thanks for the info heres where I'm at now....I switched the plugs around to the other cylinder and nothing changed so I'm going to say the plugs are fine. to add to my last update I went out played with the carbs pilot jet screw and throttle screws and managed to find a combination that would keep the cylinder going. when I'd pull the wire from the known good cylinder you could see a signifigant drop in rpms. I put everything back together as it was protective plates etc fired it up dead cylinder again. It doesn't make any sense to me. Is it possible that the magnetron for the coil isn't producing enough of a spark to that cylinder? sounds dumb when I see it written out. the other thing that I'm considering is could there be someway of having a fuel supply problem to that valve? not sure how that can be either because it's a t type setting with the fuel dumbing into one area and then a branch leading to each cylinder. it just doesn't seem to make sense what's going on. I can't see it as a valve problem if it was some how fixed and then dies again could it? It's late here I'm going to go sleep on it and see what suggestions you guys can come up with for me to try with the new info in the morning

thanks again the mystery continues

    Bookmark   August 28, 2007 at 11:32PM
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"I can't see it as a valve problem if it was some how fixed and then dies again could it"

Last post, off line 2 - 3 days, This is typical of loose valve seat.

Walt Conner

    Bookmark   August 29, 2007 at 8:18AM
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"I put everything back together as it was protective plates etc"

"It doesn't make any sense to me. Is it possible that the magnetron for the coil isn't producing enough of a spark to that cylinder?"

I'm kind of wondering if the plug wire itself might be shorting to ground?? It might be a "marginal" type thing where depending on which way the wind blows, state of the moon, humidty etc. as to if it's going to short or not.:-)
Maybe a new spark plug in that cylinder would get it "over the hump" temporarily. Plugs can look good and still fail when under actual engine compression.

I agree about the carb not being an issue, since it only has one Jet and feeds both cylinders.

Walt has a good point about a loose valve seat "moving around", causing it to run better to worse erratically.

    Bookmark   August 30, 2007 at 12:10AM
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well this is getting annoying....did the compression test and the stupid thing is I have higher compression on the "dead" cylinder then I do on the "live" one. The compression on the "dead" cylinder showed 120 psi. the "live" one showed 105-110 psi. the compression to me seems fine unless I'm missing something. I'm leaning seriously now back to my first guess of the coil being screwed or more on the lines of what bill thinks as when all things are aligned some how the wire is grounding out. I'm going to try and get a new coil assembly and switch it out and see what happens...I'll keep you guys posted and if I figure it out I'll be sure to come back with the final results nothing worse then looking for an answer and someone doesn't come back to say how they fixed it heheheh

    Bookmark   September 4, 2007 at 12:03PM
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I have had a failing coil give me the same hair pulling
fits you are having now. I kept at it, it kept coming and
going, and so on, this was on a riding mower. I pulled
the kill wire off and ran the engine, and it did better, for longer. Thinking that there was something up to that,
I did a volt reading on the kill wire, and it read @3-4
volts, traced it down to a couple of wires with chewed up
insulation that were real close. It slowly killed that
coil, 12 volts would have killed it quickly. A squirrelly
problem like yours could be the same scenario. I had
intermittant spark on one side, but it would come and go.

A higher compression reading on the "dead" side would
probably be due to unburnt fuel in the cumbustion chamber,
flooding and kicking up your reading.

If I am correct, just switching coils would only work
for a little while, until the new $50 coil was damaged.

I am assuming your engine has an electric start, etc.

Just check for voltage at the "kill" wire, with the keyswitch in all positions, and the wiring being "jiggled",


    Bookmark   September 4, 2007 at 3:15PM
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Well based on Fish's thinking, here is a real wild idea. Find a spare plug wire long enough to extend the shortest plug wire to where it will reach the farthest plug. Plug it into the short wire to extend it. Switch the plug wires and see if the "dead" cylinder now comes to life and the other one is "dead".

The coil on this engine fires both plugs at the same time each time over so it doesn't care which wire is on which plug.

I personally have never experienced only one side of one of these coils going bad but perhaps it can from what Fish says.

Walt Conner

    Bookmark   September 4, 2007 at 10:30PM
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Well the results are in.......the problem was indeed the coil. I went out fooled with it some more then asked a local guru his thoughts and I brought up the idea on changing the coil wires around(that I'd tried once already and failed at) and he said he'd never tried it before but the important thing was if I was going to do it was to at least put the other plug for the shorter wire (which luckly was the dead side in to avoid any wire length problems) into the wire and ground it out on the engine to complete the ciruit. That's the part I didn't do about a week ago was ground out the other wire. Turns out that you can have a faulty side to these solid case coils. so anyway I did the test with the grounding out of the other wire and whammo first crank of the motor and it took off. so I went got a new coil today and everything seems perfect....now one last question does anyone know the torque sequunce for the head? I had the head for that side off to clean it up and now I need the torqing sequence for it to finish it off right....thanks again guys for all the help hope this stuff helps someone else

    Bookmark   September 6, 2007 at 12:13PM
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The head torquing sequence is not that all important, but
checking the kill wire circuit is.
Did you do that?


    Bookmark   September 6, 2007 at 4:13PM
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hey fish....no I haven't checked it yet it but I'll see if I can find it and check it out before I blow this coil too...thanks and any tips on what I'm looking for would be awesome

    Bookmark   September 7, 2007 at 5:06PM
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Hi, I have a problem with starting my Lawn Tactor, I hope you can help.

First some Specs: It is a (heap of junk - ha) B&S 18hp Twin I/C M/No: 422707 Type:1263 01 Code: 9312065A
on a Murray Lawn Tractor. It doesn't appear to have any form of fuel pump unless it is part of the carb. (I believe it is gravity fed).

A little history: For some time I had been having to leave the choke on just a little to make the thing run smoothly. The last time I used the machine I fiddled a little with the various adjusting screws on the carb. with no improvement, so I set them back to where they were.
I figured I could live with the choke being out a little.

My problem is that the last time I used the machine it died on me after about 1-2 hours mowing and simply would not start again. I figured it had simply overheated so I pushed it into the garage.

Now (a week later) it doesn't want to start, or if it finally does (after lots & lots of starter motor winding), it is only for a brief period and it will run like a pig and backfires and soon dies.

It smells strongly of fuel during starter motor winding.
When I pull the plugs out after this (and having not started), they are wet with fuel.

This makes me think there is a spark problem or a timing problem.

I have tried the following:
I have replaced the plugs, I know all 3 of the kill switches are working (I checked them with a multi-meter), I made sure the earth wire to the ig. coil wasn't shorting and was working properly with ig. key switch, I pulled the coil off and checked the winding with ohms on multi-meter (this was ok), The coil is approx. one millimeter away from flywheel which I think is fine, I have checked for spark from both leads (with spark test pen) and this seems to be working, I have removed the plugs and grounded them then wound it over and they both have spark (maybe a little weak ?? not sure), I asked a mower shop guy if this thing runs points and as I suspected it is electronic timing (so I don't believe it has anything I can adjust), I even pulled the flywheel off to check there was not a sheared key or something there that may explain the timing being out (key and keyway was fine), I tried starting it without the air filter (just in case some blockage - no help but desperate), I have sprayed some engine start spray directly into each of the cyclinders through spark plug holes and after some winding got it to start and got a "Really Cool" backfire.

I am suspecting the coil is "Kangaroo-Edward" ("Roo-Ted" for non Australians) but do not know how else to test it (other than how I have stated above) or whether the spark it is putting out is as strong as it should be.

(I thought of letting the wife hold the spark plug lead end and depending on her reaction it might of given me an idea of how strong the spark was - ha ha - but I thought better of it).

I didn't want to buy a new coil if it wasn't the problem.

I don't believe it is a fuel problem due to the fact the plugs are wet.

Am I wrong in my deduction of it being Spark/Timing and what else can I do???

Please help me Fellow Lawn Tractor Guru's, before I just set fire to it and roll it down a hill or beat it with a stick. I know this won't fix it but boy would it make me feel gooooooood!!!

(I have read through many of the other peoples problems on your forum and I felt they were all a little different to mine - Please help!)

Thanks in advance for any help you can offer.

P.S. By the way, I noticed a few people in your forum having a problem with the charging of the battery. I too have suffered this problem in the past.

I thought I would mention that when I pulled the flywheel off, that the amount of dirt/dust build up inside of the flywheel and around the stator was amazing. It was packed in solid and coating the magnet faces and stator faces. I hosed all of this away, cleaned the stator faces, blew it all dry and sprayed it all with CRC/RP7 before putting it back together. I wonder if this may be a major part of the problem. I don't know if it has fixed the problem yet because my machine is not running, but I reckon it can only help. I hope this helps.

    Bookmark   April 5, 2008 at 9:06AM
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Hmm posting to two threads, suggest you stay with your original thread.

Walt Conner

    Bookmark   April 5, 2008 at 10:15PM
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Hi Walt,

I posted this thread here by mistake prior to posting the other one in the correct place. I had gone through the various other peoples and thought I was in the correct place to post it.

I felt rather silly making this simple mistake and was not sure how (if even possible) to remove it.

Regards Kev.

    Bookmark   April 5, 2008 at 11:04PM
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This posting is to request that "Walt" send me the "correct" valve adjustment procedure and the "external" compression release test process.



    Bookmark   May 17, 2011 at 12:49AM
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