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View Full Version : Small Gas Engine - Weak Yellow Spark, with a twist



Tony
06-14-2015, 03:02 PM
I'd wager most of you, when you read that title, already had a mental list of what'd
gone wrong. :)

Let me tell you a quick little story, maybe save some of you some time, or maybe its
just me, not keep'n up with the times.

Early AM decided to roll out the logsplitter and stack some wood.. worked about an hour
till my kids came round.. shut 'er down, took a play-break.

When I came back it wouldn't start.

It's a 6.8hp "Axo" engine -- my equivalent of harbor freight I think -- and I've been waiting
for this day to come around; for the engine to turn into a headache.

Gas? check. Air? check. Spark? .. no spark! Grabbed a new plug.. still no spark. Oh boy.

Started break'n her down to pull the engine. Maybe a shorted wire? As I was getting the last
mounting bolt out, and I turned the engine around, I noticed it was missing what appeared to
be a 2nd dip stick plug/cap on the back. This thing has 2 dip sticks?

Maybe it was a good thing it shut down when it did, I might've burned the engine up! No sign
of the missing cap. Mental note: check oil, cap the hole.

Tore the whole engine down.. checked wires, coil, magnet, gap, etc.. all seemed okay.. until
I found a 'spare wire' that terminated in what looked like a sensor in the casting.

Temp sensor?

Long story short, I pulled that sensor wire and my big bright blue spark came back.

This cheap-o engine has an oil level sensor in it!

Again, maybe just me, but i don't even think my 98 Jeep Cherokee has an oil level sensor. :p

After 3 hours, put it all back together, topped off the oil, started up on the first pull.

I've been kicking myself since.

Tony

Black_Moons
06-14-2015, 03:30 PM
This cheap-o engine has an oil level sensor in it!
Again, maybe just me, but i don't even think my 98 Jeep Cherokee has an oil level sensor. :p
After 3 hours, put it all back together, topped off the oil, started up on the first pull.
I've been kicking myself since.
Tony

All the cheapo engines iv seen for sale at princess auto seem to have oil level sensors. I can only imagine how many engines they had to replace from low/no oil level before they decided to install them all.

Willy
06-14-2015, 07:25 PM
I've heard of more than one person go way out of their way in order to bring something into the repair shop only to be told that it's low on oil. Most people don't bother reading the instructions that come with equipment, even after the fact.
At least you figured it out for yourself.

I've always though it was a bit silly that the sensor did not kill the ignition when the level dropped to a dangerously low level, much like some pressure actuate systems.
Having an engine not start after the oil level reaches a low level is like closing the barn door after the horse is out, one can do a lot of damage before the engine is shut down.

A.K. Boomer
06-14-2015, 07:38 PM
Tony don't feel bad - probably about 25 years ago I tracked down an AC "problem" that the customer was complaining about it coming on in the winter time,,, went through it with a fine tooth comb and found that a cam lobe used in the heater systems control was actually coming in contact with a micro switch when the defrost was being used would also turn on the AC too........ told the boss I found it but said it almost looked factory intentional - then he simply stated "that's because it is"

Duh.... never forgot that one i'll tell ya...

Willy
06-14-2015, 08:07 PM
then he simply stated "that's because it is"



They've been doing that for a long, long time, even on partial defrost. It comes on to dehumidify the air so that the windshield remains clear. Below freezing a tempersture sensor, often the engine intake air temp senor, will not allow the A/C to function. I've had my fair share of those complaints as well. Amazing what a trip through the owners manual will bring forth. Small wonder many come on DVDs and thumb drives now, may as well save some trees as no one reads them anyway. I personally know 4 people that have bought new cars this year and when I asked about certain features they haven't a clue as they don't even know or care where the owner's manual is.

Mind you there was one occasion when I spent considerable time "repairing" an under hood light that would work fine and yet after a while it would not work again. After looking through the manual I found out that after 40 min. the body computer would cut all power to the lights so as to save the battery in the event a light was inadvertently left on.:o


Almost a subject for a new thread. Sorry Tony, couldn't resist

A.K. Boomer
06-14-2015, 08:18 PM
yup and in fact was more like 30 years ago...

but it's not just to suck the humidity out for defrost mode - although that being the main reason,,,

running the AC unit occasionally is beneficial for the pumps longevity - in fact a sitting pump that still is catching all the engines vibration with parts in the same spot and bearings not being lubricated will indeed cause "False Brinelling" or "fretting wear" and can and will shorten the life of the pump, lots of other components in the pump going through the same thing...

connecting it to the defrost actually gets two very important things accomplished... otherwise many would find an unpleasant surprise when firing up the old AC unit come summer...

Boostinjdm
06-14-2015, 08:19 PM
Those low oil kill switches are kinda touchy and will kill the ignition for a few seconds. I trip the one in my skid loader (honda clone engine) from time to time going over rough ground or up steep inclines. By the time the engine sputters it's over. Shut the key off and wait a minute or two. Then fire back up on wide open throttle and no choke because the engine is borderline flooded from the shutdown.

oldtiffie
06-14-2015, 09:48 PM
All of those things seem to be covered at start-up POST (power on self test) on my Mazda3.

I leave my car air conditioning "ON" and set at 25 degrees C full time - all year round - as I've been caught (with a previous car) with a "loss of charge" in my air-conditioning compressor twice - never again!!. Cost of additional air-conditioning is way below the cost of servicing or replacement of the AC compressor.

As regards my mower and other 4-stroke gasoline engines, I always check the oil every time I start them at the start of the day - never a problem.

If I do have "loss of spark" its invariably a wrong position of the start/stop lever or a safety interlock just doing its job. Once I realise what the cause is (usually me) I give myself a severe admonishment and a big kick in the ar$e and away I go - lesson learned. punishment administered, swear it won't happen again and away I go rejoicing - until the next bl**dy time!!

Tony
06-15-2015, 08:58 AM
Black: I had the same exact thought, how many burnt up engines did they get before adding the sensor to the
cost of goods?! Which is interesting on quite a few levels if you think about it.

Usually I don't appreciate 'idiot-proofing' by manufactures, but I'll admit it saved me some money this time.
Then again I wouldn't have had the problem in the first place is there wasn't a second oil cap hidden 'round back.

But, if this came from the makers of the spill-proof gas can, I suppose they just redeemed themselves. ;)

-Tony

Forestgnome
06-15-2015, 03:43 PM
Like someone else said, oil level sensor. Briggs Industrial engines have them. Kills the spark.

Black_Moons
06-15-2015, 03:55 PM
I've heard of more than one person go way out of their way in order to bring something into the repair shop only to be told that it's low on oil. Most people don't bother reading the instructions that come with equipment, even after the fact.
At least you figured it out for yourself.

I've always though it was a bit silly that the sensor did not kill the ignition when the level dropped to a dangerously low level, much like some pressure actuate systems.
Having an engine not start after the oil level reaches a low level is like closing the barn door after the horse is out, one can do a lot of damage before the engine is shut down.

No, Its wired to the ignition system, Iv seen it on engines with NO starter at all. If oil level falls while its running, it will kill the motor.

Of course, question is, is that level still high enough for the engine to function properly. did OP's engine lose oil while sitting? maybe some got stuck in the cam shaft area or he left it on an incline? Or maybe the oil contracted/defoamed after cooling down (And had burned some while running).

Maybe the sensor was stuck.

Black_Moons
06-15-2015, 03:59 PM
I leave my car air conditioning "ON" and set at 25 degrees C full time - all year round - as I've been caught (with a previous car) with a "loss of charge" in my air-conditioning compressor twice - never again!!. Cost of additional air-conditioning is way below the cost of servicing or replacement of the AC compressor.

A good idea, But I might suggest you go one step further. in the fall/winter months, while its still above freezing, force the AC to come on by setting the temperature stupidly low. Just a few minutes every couple months will get all the compressor oil through the system, recoat all the surfaces, keep rust/whatever happens in AC systems from happening, etc.

I say this because at 25c, depending on where you live, it could easily be 6+ months without the AC unit kicking on.

CarlByrns
06-15-2015, 05:07 PM
I've always though it was a bit silly that the sensor did not kill the ignition when the level dropped to a dangerously low level, much like some pressure actuate systems.


Every one I've ever seen does just that- grounds the mag and kills the engine. They're just a simple float switch on Briggs. They're pretty popular on engines that are expected to run for a long stretch without anyone tending them, like gensets or pumps.

Willy
06-15-2015, 05:10 PM
Early AM decided to roll out the logsplitter and stack some wood.. worked about an hour
till my kids came round.. shut 'er down, took a play-break.




The OP lost the oil while it was running, it would not re-start after a rest break. He discovered that the second oil fill/dipstick (very common on most small engines) had come out while it was running.

I'm not sure how low the oil level was at this point but have seen this same scenario numerous times on Honda engines. No start condition until a lot of oil was put back into the sump. One 13HP honda just had a sump full of smoke before it was topped off! Yet these same engines ran until it was time to re-start, much like the OP's engine.

How low does it have to be?

CarlByrns
06-15-2015, 07:04 PM
The OP lost the oil while it was running, it would not re-start after a rest break. He discovered that the second oil fill/dipstick (very common on most small engines) had come out while it was running.

I'm not sure how low the oil level was at this point but have seen this same scenario numerous times on Honda engines. No start condition until a lot of oil was put back into the sump. One 13HP honda just had a sump full of smoke before it was topped off! Yet these same engines ran until it was time to re-start, much like the OP's engine.

How low does it have to be?

Good question. I think it depends on the engine- FWIW on my genset oil level is the third thing to check under 'no start' after fuel and ignition switch.

Willy
06-15-2015, 11:43 PM
Carl, in all honesty I have yet to see an engine destroyed, even the 13 HP Honda I spoke of previously, but the issue I have is the fact that while the oil level is too low to start safely, yet it's still good enough to run??

I'm thinking that 13 HP Honda with little more than smoke in the sump has had it's longevity compromised somewhat. That thing was working hard on a hot day and running fine, someone shut it off to refuel when the no start issue reared it's head upon re-start. After a very healthy oil top up it was on it's way again. Personally I'd like to see it shut off earlier especially when it is already too low to start.

Must be a bit of a balancing act though trying to read an oil level at 3,600 rpm.
Apparently done successfully with smoke and mirrors.:)

Black_Moons
06-15-2015, 11:53 PM
Carl, in all honesty I have yet to see an engine destroyed, even the 13 HP Honda I spoke of previously, but the issue I have is the fact that while the oil level is too low to start safely, yet it's still good enough to run??

I'm thinking that 13 HP Honda with little more than smoke in the sump has had it's longevity compromised somewhat. That thing was working hard on a hot day and running fine, someone shut it off to refuel when the no start issue reared it's head upon re-start. After a very healthy oil top up it was on it's way again. Personally I'd like to see it shut off earlier especially when it is already too low to start.

Must be a bit of a balancing act though trying to read an oil level at 3,600 rpm.
Apparently done successfully with smoke and mirrors.:)

I wonder if it reads oil level someplace *after* the oil pump?

That would mean it would shut the engine off as soon as the oil pump started to suck air (or at least not be able to push oil past the float switch.. though foamed oil might not support the float!), but the oil level would also go down after shut off, and it wouldn't be able to start with a low oil level that it could otherwise run at.

if it read it before the oil pump, the opposite would happen, As soon as it started and filled the cam area with oil (and the crankshaft splashed oil around) it would die due to oil level dropping.

Willy
06-16-2015, 12:02 AM
Splash lubrication, no oil pump, hence my previous comment about pressure actuated shut down systems. These are strictly oil level sensors.

Boostinjdm
06-16-2015, 01:53 AM
They can be stupid low and still survive. We used to run briggs flathead racing engines at about a third of recommended oil IIRC to cut down on parasitic drag. We also were changing oil roughly every 30 minutes of run time.

Fasttrack
06-16-2015, 12:51 PM
Carl, in all honesty I have yet to see an engine destroyed, even the 13 HP Honda I spoke of previously, but the issue I have is the fact that while the oil level is too low to start safely, yet it's still good enough to run??


I have! When in high school I used to raid the neighborhood trash for old lawnmowers. I found one by the side of the road and knocked on the door to ask the homeowner if I could take it. They said, "sure, but it ain't going to do you any good. It's broke!". I started asking questions and come to find out that they never changed the oil or topped it off since they bought it. He said he was running it one day when he heard a loud bang it stopped running after a bunch of smoke poured out. When the cord was pulled, it made funny noises.

Well I took it anyway - I figured I could scavenge a few parts off of it. As I dug my way through years of caked on grass clippings, I discovered a large hole in the crankcase. Disassembly showed that the piston had friction welded to the aluminum cylinder bore and the connecting rod snapped. The piston could only be removed by pushing it down into the crankcase. There was a big piece of the bore welded onto the piston skirt. Pretty amazing, actually.

So somewhere between never oiling it and allowing a blanket of grass clippings to surround it, the engine seized in spectacular fashion.

Willy
06-16-2015, 05:00 PM
I've seen lots of destroyed small engines in the past as well, they do take a lot of abuse before totally checking out as a rule. But so far, and I find this surprising, I have not seen those equipped with an oil level sensor burn themselves up. Well not in one session at least.
Was the engine you found equipped with a low oil level ignition cut out switch or was this a case of it dying from abuse and neglect?

CarlByrns
06-16-2015, 05:47 PM
Carl, in all honesty I have yet to see an engine destroyed

The Briggs Vanguard horizontal crank will throw a rod if low on oil and I have the customers ('field testers') to prove it. That engine has full pressure oiling.


even the 13 HP Honda I spoke of previously, but the issue I have is the fact that while the oil level is too low to start safely, yet it's still good enough to run??

Every oil level system I've seen grounds ignition so no oil, no start, no run.



Must be a bit of a balancing act though trying to read an oil level at 3,600 rpm.
Apparently done successfully with smoke and mirrors.:)

Not really. In a splash-lubed engine, the majority of the oil is in the sump, where a float switch (which may be in a baffle 'box') can detect a low-oil condition.

Someone else mentioned B&S kart engines- one of our mechanics raced one and was lubricated with very little (but expensive!) oil. Ran just dandy.

Small engines are amazingly durable given how little they cost and how inexpensively they're made (while meeting emissions requirements, no less). I've seen Vanguards with over 4000 hours on the Hobbs running great.

Fasttrack
06-16-2015, 06:25 PM
I've seen lots of destroyed small engines in the past as well, they do take a lot of abuse before totally checking out as a rule. But so far, and I find this surprising, I have not seen those equipped with an oil level sensor burn themselves up. Well not in one session at least.
Was the engine you found equipped with a low oil level ignition cut out switch or was this a case of it dying from abuse and neglect?

:) Oh no - it was dead from abuse and neglect. No low-oil level sensor on it. When you said you had yet to see an engine destroyed, I figured folks up in Canada were just more conscientious than the yuppies in the neighborhood I grew up in!

Willy
06-16-2015, 09:40 PM
Every oil level system I've seen grounds ignition so no oil, no start, no run.
.

Thanks Carl, yes this is the same as was the case with the OP's engine and the Honda I mentioned, my issue is the fact that while it won't start, it will run at that level. Moot point perhaps as I have already mentioned


:) Oh no - it was dead from abuse and neglect. No low-oil level sensor on it. When you said you had yet to see an engine destroyed, I figured folks up in Canada were just more conscientious than the yuppies in the neighborhood I grew up in!

No, no outbreak of conscientious, mechanically inclined consumers here The same abusive and neglectful ideology flourishes here as well, only the color of the license plates are changed to differentiate the two, oh and maybe the brand of their favorite, to die for, frozen cappuccino.

Speaking of this lot, I see looking at the new Sears lawn and garden brochure that B&S have brought out an engine that never requires an oil change (http://www.jsonline.com/business/new-briggs--stratton-lawn-mower-engine-never-needs-an-oil-change-b99433283z1-290423731.html)for the life of the mower!
Not that you can't or shouldn't change oil, you just don't have to, only top it up now and then when needed. This last point will be a challenge for many I'm sure.
The army of abuse and neglect have recruited another soldier.

From the link above.

"People don't buy something with the idea of maintaining it for 10 or 12 years. Unfortunately, that's not the mind-set anymore," said Patrick Hanson, an engine mechanics instructor at Milwaukee Area Technical College.



Strange thinking this disposable lot. I change oil on my heavily used power equipment mid season and then once again at the end of the season so that it's parked with clean oil off season.
The thinking that people can't be bothered puzzles me. They spend an entire season mowing and watering a lawn, yet can't be bothered to spend a couple of bucks and 15 minutes to change oil once a year.:confused:

Tony
06-17-2015, 10:09 AM
Well it appears then that it's me desperately behind the times.

Next thing you'll tell me is that they automatically shut down if they run out of gas. :o

Then engine is new.. it'd probably only seen 6 hours of run time prior to this
'incident'. My only thought was fresh gas and an air filter check.

Puckdropper
06-17-2015, 10:01 PM
Well it appears then that it's me desperately behind the times.

Next thing you'll tell me is that they automatically shut down if they run out of gas. :o

Then engine is new.. it'd probably only seen 6 hours of run time prior to this
'incident'. My only thought was fresh gas and an air filter check.

Mine has that feature... I've developed a work around by simply starting to mow at the farthest point away from the gas can and work my way back! Once it went in to automatic no-fuel shutdown over by the neighbor's yard and that's a long way to haul a 5 gallon gas can.

Just out of curiosity, do any mowers have an oil view tube or some sort of gauge? Put it where I can see it, and I'll take a quick look when I go to mow.