hot engine won't start

[DEKE]

We have a 3.5 HP Briggs powered pressure washer.  The carb gums up ALL THE TIME.  I've had to take it apart and clean it every time DW forgets to run the gas tank dry. 

Almost every time we use it, after we refuel it will not restart for at least 30 minutes.  Starter fluid doesn't help. Any ideas on what might be wrong?  

[Tim Horton]

At one time I had a chain saw that was like that.. Cold start on second pull, run like a champ, but would not restart hot..

Took it in to have it diagnosed, set it on the counter and told the guy what it does, him saying fly wheel magneto issues.. Seen it a hundred times.. I took it back home and when it was dull and out of gas took it to paid metal recycle.

It would cost more to fix it than to apply that money to a new saw.. I only gave $5 for the old saw at a garage sale..

++++++++

I have 2 cheap 20" mowers with B&S 3.5 hp motors that will not start cold.. You have to take the recoil starter off, spin them with a socket in a drill on the fly wheel nut and hold your hand over the end of the carb to choke them.. Once warm they both restart OK.. First start of the day is a bugger..

Suggestions ??

[Ozarks Tom]

I had a tiller that didn't like starting hot sometimes. Don't know why just now and then, just the way it was. I found putting it on full choke for a pull or two would get it going again. Shouldn't have to choke a hot engine, but that's the only thing that worked for me.

Hey, where's Joebill when we need him?

[Thtwudbeme]

Jun 5, 2020 12:44:04 GMT DEKE said:

We have a 3.5 HP Briggs powered pressure washer.  The carb gums up ALL THE TIME.  I've had to take it apart and clean it every time DW forgets to run the gas tank dry. 

Almost every time we use it, after we refuel it will not restart for at least 30 minutes.  Starter fluid doesn't help. Any ideas on what might be wrong?  

Briggs and Stratton is the first thing that comes to mind.  At one time they produced a good engine, but that was a long time ago.

The second thing that comes to mind is that you seem to run it with ethanol gas.  Why?  Non-ethanol may cost a bit more, but I have never had any problems with my small engines when running non-ethanol through them, especially not gumming issues.

[DEKE]

I'm sure you're right when the gas is left in it. Doesn't make sense to me when it's been running fine, you refuel, and then it won't restart until it cools down.

[farmrbrown]

Jun 6, 2020 3:08:49 GMT DEKE said:

I'm sure you're right when the gas is left in it. Doesn't make sense to me when it's been running fine, you refuel, and then it won't restart until it cools down.

It could be a couple things that will make sense.
1) A vapor lock. Usually won't happen in a small engine but I've seen it before. Really inconvenient if you're in the middle of a lake with a thunderstorm looming.
2) Had a few chainsaws that did it and concluded that the rings, pistons or cylinders were expanding from the heat and causing  problems, either seizing so you couldn't even pull the cord or so sloppy that you lost compression.

Don't know if it'll help but if it's #1 you might cool the fuel and lines and see if that's it. If #2, it won't be easy like holding a cold beer. 

[fordy]

Jun 5, 2020 12:44:04 GMT DEKE said:

We have a 3.5 HP Briggs powered pressure washer.  The carb gums up ALL THE TIME.  I've had to take it apart and clean it every time DW forgets to run the gas tank dry. 

Almost every time we use it, after we refuel it will not restart for at least 30 minutes.  Starter fluid doesn't help. Any ideas on what might be wrong?  

................Engine gets hot , head gasket expands  , may have warped head from heat , ? Remove head , take a metal ruler and run it across block and head and look for gaps where light shines through ! Both surfaces should be flat !

................You can buy a Chonda(Chinese Honda) new engine replacement for ~$120 @ Northern tool , and or Harbor freight ! , fordy 

[DEKE]

Jun 6, 2020 3:22:51 GMT farmrbrown said:

It could be a couple things that will make sense.
1) A vapor lock. Usually won't happen in a small engine but I've seen it before. Really inconvenient if you're in the middle of a lake with a thunderstorm looming.
2) Had a few chainsaws that did it and concluded that the rings, pistons or cylinders were expanding from the heat and causing  problems, either seizing so you couldn't even pull the cord or so sloppy that you lost compression.

Don't know if it'll help but if it's #1 you might cool the fuel and lines and see if that's it. If #2, it won't be easy like holding a cold beer. 

I had always assumed vapor lock, but you may be closer on loss of compression.  I assume that little resistance when I pull the starter cord means the compression is low.  Yes?  I know next to nothing about engines but I thought low compression when DW asked for help. 

There is way too little resistance when I tug the starter cord.  It is DW's toy so I never start it cold.  I'll try it tmr and see if a true cold start has more of a standard resistance on the cord.   

[Deleted]

Jun 6, 2020 1:26:28 GMT Thtwudbeme said:

Jun 5, 2020 12:44:04 GMT DEKE said:

We have a 3.5 HP Briggs powered pressure washer.  The carb gums up ALL THE TIME.  I've had to take it apart and clean it every time DW forgets to run the gas tank dry. 

Almost every time we use it, after we refuel it will not restart for at least 30 minutes.  Starter fluid doesn't help. Any ideas on what might be wrong?  

Briggs and Stratton is the first thing that comes to mind.  At one time they produced a good engine, but that was a long time ago.

The second thing that comes to mind is that you seem to run it with ethanol gas.  Why?  Non-ethanol may cost a bit more, but I have never had any problems with my small engines when running non-ethanol through them, especially not gumming issues.

We always run premium (non-ethanol) gas in our small machines.

[farmrbrown]

Jun 6, 2020 4:10:35 GMT DEKE said:

Jun 6, 2020 3:22:51 GMT farmrbrown said:

It could be a couple things that will make sense.
1) A vapor lock. Usually won't happen in a small engine but I've seen it before. Really inconvenient if you're in the middle of a lake with a thunderstorm looming.
2) Had a few chainsaws that did it and concluded that the rings, pistons or cylinders were expanding from the heat and causing  problems, either seizing so you couldn't even pull the cord or so sloppy that you lost compression.

Don't know if it'll help but if it's #1 you might cool the fuel and lines and see if that's it. If #2, it won't be easy like holding a cold beer. 

I had always assumed vapor lock, but you may be closer on loss of compression.  I assume that little resistance when I pull the starter cord means the compression is low.  Yes?  I know next to nothing about engines but I thought low compression when DW asked for help. 

There is way too little resistance when I tug the starter cord.  It is DW's toy so I never start it cold.  I'll try it tmr and see if a true cold start has more of a standard resistance on the cord.   

I saw this thread/link last night but didn't get around to reading it until today.


forum.mrmoneymustache.com/do-it-yourself-forum!/lawn-mower-will-not-start-when-hot/

As you can see nearly every person had a different answer, including the ones we offered on this thread. 
I would check all the bolts holding the carb and the engine too. They might be a little loose and allowing some air leakage. I can't stand working on small engines but I've found the tiniest imperfections in reassembly, gasket seals, hoses, etc. can make all the difference so don't overlook small things because they do matter.

Those bad chainsaws I had were Poulans, brand new out of the box and in less than 50 hours the cylinders looked like they were shot with rock salt. The "factory authorized dealer" had the audacity to say I must have used straight gas in them with no oil. I didn't even bother to reply to that idiot. I've been doing yard work since I could ride a bicycle and have NEVER used the wrong fuel in ANY motor.
What I DID do was follow the manufacturer directions and learned from that mistake. I went back to old school ways and started mixing more oil in the fuel ratio and haven't had any more trouble?
Why?
After reading hundreds of complaints about the "new emission" crapola to make 2 cycle engines burn cleaner, I realized they were making carbs run too lean and telling you to use less oil in the mix.
Well Duh! No wonder the motors are burning up! That oil is the only lubrication it gets, and running lean makes it worse!
Sorry for the rant on 2 cycles, that's not your engine, but illustrates how easily something can go wrong even if you're doing everything right, especially when they try to "improve" stuff that was working just fine.



 

[comfortablynumb]

put a compression tester on it and see what it is cold, then hot. Thats the first step. If its running hot or cold and not starving for gas its not a gas feed problem. Pull the bowl off while cold, see if its flowing. pull it off when hot, see of its flowing.

As for the magneto, it might need the air gap reset. A cold flywheel is contracted, and a hot one is expanded and, if its too close, it might be hitting the flywheel when its hot... but if that was the case it probably would die when its hot.

But start with a compression test.

Starter fluid doesn't help.

The only reason starter fluid wouldn't make it pop at least, is a bad ignition/spark. even on a low compression engine, if you introduce ether into the cyl, compress it even poorly, and spark it, its gonna pop.  This makes me think you have a bad magneto or its air gap is not right.

[DEKE]

Thanks, Numb, but you have exceeded my mechanical capabilities. I have a tenant that is quite mechanical and is always looking for a way to offset rent, I'll let him take a look at it and tell him my new magneto theory. I'll look real smart unless he asks me a question, then my bluff will fall apart fast.

[joebill]

Sorry it took a while for me to find this. B&S has a special little quirk that everybody else lacks that will shut down a hot engine with a bit of wear on it every single time.

It is called "easy spin starting" and it is an automatic compression release that is so touchy just a little engine wear can finish it off, but it can be repaired with just a little effort.

To test if this is the trouble, give the rope a little twitch to get the engine rolling over. When it comes up on the compression stroke, the flywheel should bounce back a bit, not just coast to a stop, and if it does not, it is short on compression and the gas/air mixture will not ignite without compression.

The "easy spin" quirk is an extra high spot on the cam shaft that very slightly opens and closes the exaust valve on the compression stroke...JUST A TAD, almost not enough to notice. That bleeds off just a small percent of the compression to make it easier for grandma to pull the rope.

Problem is, as the valve face and seat wear down over time, the tolerances are so very tight that the valve will not completely close any more, and compression loss becomes so great that it won't start, plus the hot temperature will expand the length of the valve, making the problem worse.

The cure is to adjust the valve clearance, but the only adjustment possible on those engines is to remove the valves and grind or even file some material off of the (small) end of each valve. The amount you remove is not critical unless you get crazy with it. Take off maybe .020 or .030. Taking off a HUGE amount would inhibit performance.

I always thought that feature was a nasty trick from the outset. Hardly anybody knows how it messes up and a lot of decent engines go to the grave over it. I dunno what a small engine shop charges these days for a valve job including setting the clearance, but odds are they will not do one without the other.

If anybody does one of these, notice the before and after differences in the rope resistance when you crank it. Pretty phenomonal!....Joe

[comfortablynumb]

Easy spin starting... I'll have to remember that one. I've had one of these engines or 2 that just refused to start and there wasn noting wrong with em. That was probably the cause.

I had one on my DR wagon that failed like this.... I gave up and replaced the engine. DR was pretty tight lipped about why they sold me a new engine for it so cheap. I asked if they had problems with the old engines they just said... um... the new ones are better. LOL

I still have that POS engine out in the barn on a shelf.