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Briggs - Gas Blowing Out of Carb
#1
G
GAVolunteer
G
GAVolunteer
Briggs Engine 127802-0640-01 95091859
Carb has primer bulb
Toro Push Mower
Problem-Symptoms:
1. Engine starts and runs great for a few minutes and then runs "rough" for 15-20 seconds and then runs smooth for another minute or so and then runs rough again.
2. After troubleshooting, I noticed that the new paper air filer was wet with gas and the bottom of the air cleaner base was wet with gas.
3. With the air filter removed, the engine runs great and does not sputter or run rough.
4. With the air filter removed, I noticed a heavy mist of gas is blowing out of the carb. I believe when the filter gets wet with gas, the engine gets starved for air and then runs rough.
5. I put a known good carb in the engine and the second carb did the same thing.
Question: What causes gas to get blown out of the carb? How do I trouble shoot this?
Background.
1. The owner of the mower was mowing in very tall gas and "hit something". This caused the dipstick to get blown out of the tube spraying oil everywhere. He could not get the mower restarted and ended up breaking the pull rope.
2. I checked the flywheel and the key was not sheared. It looked fine.
3. I cleaned the carb, changed the oil, new spark plug, new rope.
4. I checked the blade and it was not damaged. I sharpened the blade and made sure it was balanced.
Thanks for your help.
Carb has primer bulb
Toro Push Mower
Problem-Symptoms:
1. Engine starts and runs great for a few minutes and then runs "rough" for 15-20 seconds and then runs smooth for another minute or so and then runs rough again.
2. After troubleshooting, I noticed that the new paper air filer was wet with gas and the bottom of the air cleaner base was wet with gas.
3. With the air filter removed, the engine runs great and does not sputter or run rough.
4. With the air filter removed, I noticed a heavy mist of gas is blowing out of the carb. I believe when the filter gets wet with gas, the engine gets starved for air and then runs rough.
5. I put a known good carb in the engine and the second carb did the same thing.
Question: What causes gas to get blown out of the carb? How do I trouble shoot this?
Background.
1. The owner of the mower was mowing in very tall gas and "hit something". This caused the dipstick to get blown out of the tube spraying oil everywhere. He could not get the mower restarted and ended up breaking the pull rope.
2. I checked the flywheel and the key was not sheared. It looked fine.
3. I cleaned the carb, changed the oil, new spark plug, new rope.
4. I checked the blade and it was not damaged. I sharpened the blade and made sure it was balanced.
Thanks for your help.
#2
Michael72
Michael72
Key in blade adapter ok??...it might be a key or key-way built in to adaptor
#3
B
bertsmobile1
The decompressor opens up to the inlet which blows back through the carb.
This only happens at cranking speeds.
Excessive blow back can be causes by valves being out of time with crank which will also cause rough running
Roug running can be caaused by out of time spark, check the flywheel key
B
bertsmobile1
Briggs Engine 127802-0640-01 95091859
Carb has primer bulb
Toro Push Mower
Problem-Symptoms:
1. Engine starts and runs great for a few minutes and then runs "rough" for 15-20 seconds and then runs smooth for another minute or so and then runs rough again.
2. After troubleshooting, I noticed that the new paper air filer was wet with gas and the bottom of the air cleaner base was wet with gas.
3. With the air filter removed, the engine runs great and does not sputter or run rough.
4. With the air filter removed, I noticed a heavy mist of gas is blowing out of the carb. I believe when the filter gets wet with gas, the engine gets starved for air and then runs rough.
5. I put a known good carb in the engine and the second carb did the same thing.
Question: What causes gas to get blown out of the carb? How do I trouble shoot this?
Thanks for your help.
The decompressor opens up to the inlet which blows back through the carb.
This only happens at cranking speeds.
Excessive blow back can be causes by valves being out of time with crank which will also cause rough running
Roug running can be caaused by out of time spark, check the flywheel key
#4
G
GAVolunteer
Good suggestion. I did a visual check on the key the other day. It looked ok. It may be slightly sheared which would explain everything. I'll remove the key and put in a new one.
Thanks
G
GAVolunteer
Roug running can be caused by out of time spark, check the flywheel key
Good suggestion. I did a visual check on the key the other day. It looked ok. It may be slightly sheared which would explain everything. I'll remove the key and put in a new one.
Thanks
#5
T
Tinkerer200
Don't understand this connection?
Walt Conner
T
Tinkerer200
Key in blade adapter ok??...it might be a key or key-way built in to adaptor
Don't understand this connection?
Walt Conner
#6
Michael72
Just pointing out that when we know that the blades hit something that we auto look at flywheel key and sometimes the key or key-way in blade adapter is sometimes overlooked.
Michael72
Don't understand this connection?
Walt Conner
Just pointing out that when we know that the blades hit something that we auto look at flywheel key and sometimes the key or key-way in blade adapter is sometimes overlooked.
#7
G
GAVolunteer
G
GAVolunteer
I replaced the flywheel key and retested. Fine mist of gas still came out of carb.
Checked the valve clearance. Intake valve was .0025. Exhaust .007. Removed head and valves. Cleaned carbon buildup which was not too bad. Lapped the valves. Carefully filed down intake valve stem to .006 clearance. New head gasket and valve cover gasket.
I thought fixing the intake valve would fix the problem, but it did not. Mower still has fine mist of gas coming out of the carb. It hits the metal plate on the air filter base and with the air filter removed, collects at the bottom of the cover and eventually drips in the deck. If the air filter is installed, the filter soaks up the gas.
Any other ideas or suggestions? The gas issue is a real safety concern. Thanks for the help.
Checked the valve clearance. Intake valve was .0025. Exhaust .007. Removed head and valves. Cleaned carbon buildup which was not too bad. Lapped the valves. Carefully filed down intake valve stem to .006 clearance. New head gasket and valve cover gasket.
I thought fixing the intake valve would fix the problem, but it did not. Mower still has fine mist of gas coming out of the carb. It hits the metal plate on the air filter base and with the air filter removed, collects at the bottom of the cover and eventually drips in the deck. If the air filter is installed, the filter soaks up the gas.
Any other ideas or suggestions? The gas issue is a real safety concern. Thanks for the help.
#8
lugnut1
lugnut1
first guess: would have been float, needle and seat issue.
(but you changed carbs and still have same issue.)
second guess: would be timing issue.
third guess: blow bye past rings (being you did valve's)
I'd do a compression check on it, and or a leak down test.
(but you changed carbs and still have same issue.)
second guess: would be timing issue.
third guess: blow bye past rings (being you did valve's)
I'd do a compression check on it, and or a leak down test.
#9
upupandaway
From your symptoms, the gap in the valve train between the tappet and valve is too small. When u start it the gap is fine and as it heats up the gap closes too much and u get a valve left open and it sprays gas out to the filter leaving a puddle of gas. Remove the air filter and hold a sheet of paper over the air intake and it is blowing(spraying gas) the paper up instead of suck down is not normal.
To keep it simple, what i did is get a big screwdriver to pry the valve open and slipped in a file to grind it down a little and check with a feeler gauge .06 for intake and .08 exhaust i think... dont quote me on these numbers.
Don't know why but all 4 briggs 12hp i have found did this shortly after acquiring them. The last one i did about 6yrs ago, knock on wood.
Still what leaves me scratching my head is i dont see how hitting tall grass will stretch a valve but that is what the symptoms point to.
upupandaway
Briggs Engine 127802-0640-01 95091859
Carb has primer bulb
Toro Push Mower
Problem-Symptoms:
1. Engine starts and runs great for a few minutes and then runs "rough" for 15-20 seconds and then runs smooth for another minute or so and then runs rough again.
2. After troubleshooting, I noticed that the new paper air filer was wet with gas and the bottom of the air cleaner base was wet with gas.
3. With the air filter removed, the engine runs great and does not sputter or run rough.
4. With the air filter removed, I noticed a heavy mist of gas is blowing out of the carb. I believe when the filter gets wet with gas, the engine gets starved for air and then runs rough.
5. I put a known good carb in the engine and the second carb did the same thing.
Question: What causes gas to get blown out of the carb? How do I trouble shoot this?
Background.
1. The owner of the mower was mowing in very tall gas and "hit something". This caused the dipstick to get blown out of the tube spraying oil everywhere. He could not get the mower restarted and ended up breaking the pull rope.
2. I checked the flywheel and the key was not sheared. It looked fine.
3. I cleaned the carb, changed the oil, new spark plug, new rope.
4. I checked the blade and it was not damaged. I sharpened the blade and made sure it was balanced.
Thanks for your help.
From your symptoms, the gap in the valve train between the tappet and valve is too small. When u start it the gap is fine and as it heats up the gap closes too much and u get a valve left open and it sprays gas out to the filter leaving a puddle of gas. Remove the air filter and hold a sheet of paper over the air intake and it is blowing(spraying gas) the paper up instead of suck down is not normal.
To keep it simple, what i did is get a big screwdriver to pry the valve open and slipped in a file to grind it down a little and check with a feeler gauge .06 for intake and .08 exhaust i think... dont quote me on these numbers.
Don't know why but all 4 briggs 12hp i have found did this shortly after acquiring them. The last one i did about 6yrs ago, knock on wood.
Still what leaves me scratching my head is i dont see how hitting tall grass will stretch a valve but that is what the symptoms point to.
#10
T
Tinkerer200
T
Tinkerer200
What often happens is some pertain fact is accidentally overlooked, omitted.
Walt Conner
Walt Conner
#11
G
GAVolunteer
I believe I found the problem. The crankshaft is "a little" bent. I removed the blade and adapters to check the blade adapter key and pulley key. They were fine. After reinstalling the blade and pulley, I turned the blade several times and the blade bolt seemed to have a slight oval pattern. I attached a wooden skewer stick to the underside of the mower with the point of the stick centered on the bolt. When I turned the blade, I could see a small oval pattern of the bolt as it turned.
What is perplexing is that the flywheel key was not sheared yet the crankshaft appears to be bent. When the engine is running, there does not appear to be any vibration.
Would a bent crank cause the timing to be slightly off and cause a fine spray of gas to blow out of the carb?
This is a 1995 engine. Before I junk the engine for parts, I want to be sure that my diagnosis passes the "smell test". Any other tests or troubleshooting I need to do?
Thanks,
Robert
G
GAVolunteer
Key in blade adapter ok??...it might be a key or key-way built in to adaptor
I believe I found the problem. The crankshaft is "a little" bent. I removed the blade and adapters to check the blade adapter key and pulley key. They were fine. After reinstalling the blade and pulley, I turned the blade several times and the blade bolt seemed to have a slight oval pattern. I attached a wooden skewer stick to the underside of the mower with the point of the stick centered on the bolt. When I turned the blade, I could see a small oval pattern of the bolt as it turned.
What is perplexing is that the flywheel key was not sheared yet the crankshaft appears to be bent. When the engine is running, there does not appear to be any vibration.
Would a bent crank cause the timing to be slightly off and cause a fine spray of gas to blow out of the carb?
This is a 1995 engine. Before I junk the engine for parts, I want to be sure that my diagnosis passes the "smell test". Any other tests or troubleshooting I need to do?
Thanks,
Robert
#12
Michael72
The bolt might give a different reading to the shaft itself in terms of it being bent... as in the bolt is slightly bent)....Its why I mentioned the blade adapter earlier on....Was the blade fitted when you felt no vibration?.. is it burning oil?...compression rising up past piston rings wouldnt help matters....see my post.. "something to look at"... in this case the timing was out at camshaft and scored piston and cylinder...
Michael72
I believe I found the problem. The crankshaft is "a little" bent. I removed the blade and adapters to check the blade adapter key and pulley key. They were fine. After reinstalling the blade and pulley, I turned the blade several times and the blade bolt seemed to have a slight oval pattern. I attached a wooden skewer stick to the underside of the mower with the point of the stick centered on the bolt. When I turned the blade, I could see a small oval pattern of the bolt as it turned.
What is perplexing is that the flywheel key was not sheared yet the crankshaft appears to be bent. When the engine is running, there does not appear to be any vibration.
Would a bent crank cause the timing to be slightly off and cause a fine spray of gas to blow out of the carb?
This is a 1995 engine. Before I junk the engine for parts, I want to be sure that my diagnosis passes the "smell test". Any other tests or troubleshooting I need to do?
Thanks,
Robert
The bolt might give a different reading to the shaft itself in terms of it being bent... as in the bolt is slightly bent)....Its why I mentioned the blade adapter earlier on....Was the blade fitted when you felt no vibration?.. is it burning oil?...compression rising up past piston rings wouldnt help matters....see my post.. "something to look at"... in this case the timing was out at camshaft and scored piston and cylinder...
#13
KrashnKraka
I am with you on this one, cylinder pressure leaking back past an inlet valve.
Makes sense.
I am wondering if in the circumstance you describe there isn't maybe a valve
spring issue?
Like, busted partially, lost tension or even the wrong spring (temperature coefficient).
And in the OP's case he reads as very switched on so maybe he is finding an existing
symptom post the blade 'damage'.... you think?
KK
KrashnKraka
Don't know why but all 4 briggs 12hp i have found did this shortly after acquiring them. The last one i did about 6yrs ago, knock on wood.
Still what leaves me scratching my head is i dont see how hitting tall grass will stretch a valve but that is what the symptoms point to.
I am with you on this one, cylinder pressure leaking back past an inlet valve.
Makes sense.
I am wondering if in the circumstance you describe there isn't maybe a valve
spring issue?
Like, busted partially, lost tension or even the wrong spring (temperature coefficient).
And in the OP's case he reads as very switched on so maybe he is finding an existing
symptom post the blade 'damage'.... you think?
KK
#14
G
GAVolunteer
I rechecked the crankshaft with the blade and adapter removed. The amount of "wobble" was much less about 1/16th". I then checked put the blade and adapter back on and checked the each end of the blade at a fixed point. One end was 1/16" shorter. It could be the blade was shorter one one side. But it was consistent with the crankshaft measurement.
Which makes me wonder if that small amount of variance in the crankshaft would cause the timing and carb issues.
When I lapped the valves, I checked the piston and cylinder and there was no scoring.
I have not felt any vibration - before or after I removed and reinstalled the blade. IT does not appear to be burn in oil.
That was a neat test. When the paper is about 1" from the carb opening, the paper gets wet with gas quickly. That clearly showed the amount of gas blowing out of the carb. If the paper is put closer, the carb sucks the paper with quite a bit of pressure.
Also, I had already ground down the intake valve stem to .006 clearance and did a leak down test both cold and hot. See previous post. I believe the valve is closing completely.
From all of the tests and posts, I believe I have a timing issue. Looks like it is time to look inside the engine.
G
GAVolunteer
The bolt might give a different reading to the shaft itself in terms of it being bent... as in the bolt is slightly bent)....Its why I mentioned the blade adapter earlier on....Was the blade fitted when you felt no vibration?.. is it burning oil?...compression rising up past piston rings wouldnt help matters....see my post.. "something to look at"... in this case the timing was out at camshaft and scored piston and cylinder...
I rechecked the crankshaft with the blade and adapter removed. The amount of "wobble" was much less about 1/16th". I then checked put the blade and adapter back on and checked the each end of the blade at a fixed point. One end was 1/16" shorter. It could be the blade was shorter one one side. But it was consistent with the crankshaft measurement.
Which makes me wonder if that small amount of variance in the crankshaft would cause the timing and carb issues.
When I lapped the valves, I checked the piston and cylinder and there was no scoring.
Was the blade fitted when you felt no vibration?.. is it burning oil?
I have not felt any vibration - before or after I removed and reinstalled the blade. IT does not appear to be burn in oil.
Remove the air filter and hold a sheet of paper over the air intake and it is blowing(spraying gas) the paper up instead of suck down is not normal.
That was a neat test. When the paper is about 1" from the carb opening, the paper gets wet with gas quickly. That clearly showed the amount of gas blowing out of the carb. If the paper is put closer, the carb sucks the paper with quite a bit of pressure.
Also, I had already ground down the intake valve stem to .006 clearance and did a leak down test both cold and hot. See previous post. I believe the valve is closing completely.
From all of the tests and posts, I believe I have a timing issue. Looks like it is time to look inside the engine.
#15
T
Tinkerer200
T
Tinkerer200
Note that most B&S engines relieve compression via the Intake Valve so you are going to naturally get some blow back when starting and at idle. Running great then badly then great again does not sound like timing to me and the amount of gas you are describing sounds like flooding to me. By the way, when you lapped the valves,did you use Bluing or anything to be sure you had a good seat?
Walt Conner
Walt Conner
#16
G
GAVolunteer
G
GAVolunteer
Thanks for the feedback.
I did not use any bluing. Afterwards, I did a leak down test with engine cold and hot. Only had 10% leakage which I assumed indicated a good seal between the valve and seat on both the intake and exhaust valves. I could hear a little air coming from the oil dipstick tube. But not an excessive amount. Did not hear any air from the muffler or carb.
I agree with the flooding idea. There are no adjustments on the carb and I've tried two different carbs both with the same result. I assume the only cause of flooding would be a bad carb needle or seat. Any ideas on how to troubleshoot a flooding issue?
By the way, when you lapped the valves,did you use Bluing or anything to be sure you had a good seat?
Walt Conner
I did not use any bluing. Afterwards, I did a leak down test with engine cold and hot. Only had 10% leakage which I assumed indicated a good seal between the valve and seat on both the intake and exhaust valves. I could hear a little air coming from the oil dipstick tube. But not an excessive amount. Did not hear any air from the muffler or carb.
the amount of gas you are describing sounds like flooding to me.
I agree with the flooding idea. There are no adjustments on the carb and I've tried two different carbs both with the same result. I assume the only cause of flooding would be a bad carb needle or seat. Any ideas on how to troubleshoot a flooding issue?
#17
D
Deeruser
D
Deeruser
English pleaseWhat often happens is some pertain fact is accidentally overlooked, omitted.
Walt Conner
#19
S
slomo
S
slomo
Or the flywheel key and its groove.Key in blade adapter ok??...it might be a key or key-way built in to adaptor
#20
S
slomo
S
slomo
Is the spark plug black?
Take an old plug. Gap to 1/4" wide. Check for a good blue spark.
Wonder if someone put a steel key in the flywheel groove causing it to not shear??
If the crank is bent, it's done. Or find a mower shop that has a crank straightener.
Take an old plug. Gap to 1/4" wide. Check for a good blue spark.
Wonder if someone put a steel key in the flywheel groove causing it to not shear??
If the crank is bent, it's done. Or find a mower shop that has a crank straightener.
#21
KrashnKraka
This is a dead engine.
A engine no more.
Ze Injun sheeza roeted.
No more engine is woik.
--
.mea culpa Queen Victa!
KrashnKraka
Engine is pharked, done.English please
This is a dead engine.
A engine no more.
Ze Injun sheeza roeted.
No more engine is woik.
--
.mea culpa Queen Victa!