View Full Version : Problem with 44" Lazer CT with 18 HP Vanguard eng.
08-29-2008, 08:32 PM
I have a 2005 44" Exmark Lazer CT Model LCT4418BV with mod 356777 B & S Vanguard engine. The unit has 86.5 hours of homeowner use. After running perfectly for the last 3 years, it started have low power yesterday. I have changed the spark plugs, fuel, the fuel filter, cleaned the air cleaner and about everything else that I can think of. It runs fairly smooth until it is under load.
I began to suspect that it might be running on just one cylinder and I just touched the valve covers after running if for a few moments. One is fairly hot and the other is only slightly warm. My suspicions about one cylinder not firing may be confirmed by the fact that one of the old plugs was black and the other was pretty white.
Assuming that it is not firing and given that I have changed the plug, what is the likely cause?
08-29-2008, 09:40 PM
I would say the coil for that cylinder that was cold went bad.
08-29-2008, 10:10 PM
I wouldn't be so quick to replace a coil on this engine. It has a (Y) style kill lead that has a diode in each of the two legs that connect to the coils. If one of these diodes go out it will cause the coil to stop firing.
Test the kill wire lead by disconnecting the one end from the unit wire harness and then from each coil, Use a multimeter set on Ohm's scale. Put the red test lead on the unit harness plug connector and the black test lead on each of the coil plug connectors one at a time checking for a resistance or no resistance. Both coil leads should read the same, Then swap the red test lead for the black and test again but this time they should read opposite what you got before.
If the kill lead harness test good, It would be safe to say a coil took a dump.
08-30-2008, 02:03 AM
I have tracked down the parts list for this engine and have identified the Y kill lead part number. I don't have exploded drawings so I am guessing a little about what I have to remove to get to the kill lead. It looks like the blower housing has to come off and unless I am fooled, the fuel pump, muffler and maybe a couple of other things that are mounted to that housing. Does that sound right and is there anything else that I should know?
BTW, I found a statement on the B & S site that the coil rarely fails so, hopefully, it will be the kill lead.
08-30-2008, 12:43 PM
I have removed the blower housing and took out the Y kill lead. I get an open circuit on both leads no matter how I test it. I can short the meter leads and they go to zero so I know that it is not the meter. Since the engine will run, both leads can't be bad. I'm stumped at this point.
08-30-2008, 03:09 PM
I tried swapping the coils and the problem remained on the same cylinder. I first took that as confirmation that the Y kill lead was in fact bad. Before leaving to get a new one, I decided to put the long (good) wire in place of the short (bad) wire to confirm that the non-running cylinder would then run. It didn't. The cylinder that has been working kept working with the lead disconnected and the non-working one still didn't work. I then disconnected the leads altogether and the working cylinder still worked and the other still didn't.
The only thing that I can think of now is the the problem is mechanical. Is there anything else that I can try without tearing into the engine?
08-30-2008, 08:49 PM
Remove the valve cover on the bad cylinder and take a look.
08-30-2008, 11:52 PM
Thanks for the help.
One of the push rods is lying loose. It does not appear to be broken since each end had a ball shape. The other is loose on the rocker arm but seems to be attached the the valve or at least it has not fallen out.
The next question is how easy is this to fix? If I take it in to a shop, what should it cost to have it fixed. The engine is 3 years old but only has 86 hours. It sure doesn't seem like this should have happened.
08-31-2008, 01:11 AM
Lay the push rod on a flat surface and make sure it is not bent. If it is chances are you have a lifter or valve that is sticking especially since you dont put very many hours on it. I have heard of guys that put some marvel mystery oil in the engine and it frees em up. If its not bent just put it back in and adjust your valves at .004-.006. If you do take it to the shop I would put it back together first, I personally charge more for things that are torn apart when they come in.
08-31-2008, 03:00 AM
Make sure the valve guide bushing hasn't backed out.
This can cause the posh rod to bend and then fall out.
Go to the Briggs site and down load the IPL for your specific engine to see an exploded drawing.
08-31-2008, 09:29 AM
One point of clarification. The loose push rod appears to be the push rod for the tapped valve and it looks to be straight.
This is dumb but I have to ask. Should I go ahead and remove the cylinder head and re-assemble it on the bench or can I just remove the rockers and re-assemble it in place? Also, how does the push rod attach to the valve? Is it just a friction fit?
08-31-2008, 09:50 AM
You should not have to remove cylinder head to reposition push-rod. Just loosen the rocker assembly and put the push-rod back in place. You can then adjust the valve lash according to specs . You probably should go on and adjust both cylinders while you have it down.The push-rod fits down thru the cylinder and into the top of the lifter. The top of the push-rod you will see fits in the indention on the opposite end of the rocker from the valve stem.
08-31-2008, 03:42 PM
OK, first of all, thanks to everyone who contributed to this thread. In the course of about 36 hours, I went from not having a clue what was wrong to having both cylinders firing. I still have to adjust the tappets on the other cylinder and then see if I can remember how to reassemble everything but so far so good.
I followed your leads and also found a B&S reference on their site to reassure me. Both push rods were straight and true. Both valves seemed to move freely as I moved the flywheel by hand, so I just reinstalled the push rods and adjusted the tappet's clearance according the the B&S specs. Both appear to have been on the loose side which I assume caused one to simply drop out with the resulting trauma taking the other one with it.
Thanks again for the help, I was really, really dreading having to borrow a trailer and then hauling this puppy 30 miles to the shop. Hopefully, this will be the last time that I have to do this job.
09-01-2008, 07:16 PM
It would be safe to say a coil took a dump.
Ha haa :laugh: straight out of the workshop manual. I love this technical talk.
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