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B&S model 31H7770202E1 18 HP (craftsman LT1000)

#1

PamG

PamG

This engine is on a craftsman riding mower and will only run for 20 minutes from cold, and then 15 minutes after a 20 minute cooldown. Heat seems to be the issue. Have checked oil, airfilter, cap, plug and changed away from ethanol gas. It literally just dies…no rough running at any time. Someone on another forum suggested it could be the ignition going to open circuit when getting hot. Any suggestions?


#2

ILENGINE

ILENGINE

Ignition would be my first guess, but will need to confirm loss of spark after engine dies with a open gap spark tester, not a blink style tester. Need possible could be a failing fuel solenoid on bottom of carb, but that is not as common but does happen.


#3

PamG

PamG

ILENGINE said:
Ignition would be my first guess, but will need to confirm loss of spark after engine dies with an open gap spark tester, not a blink style tester. Need possible could be a failing fuel solenoid on bottom of carb, but that is not as common but does happen.
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My seat has a sensor on it so the engine dies if I stand up…and that’s exactly how this engine is acting…like I got out of the seat at the 20 minute mark.


#4

PamG

PamG

PamG said:
My seat has a sensor on it so the engine dies if I stand up…and that’s exactly how this engine is acting…like I got out of the seat at the 20 minute mark.
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ILENGINE said:
Ignition would be my first guess, but will need to confirm loss of spark after engine dies with a open gap spark tester, not a blink style tester. Need possible could be a failing fuel solenoid on bottom of carb, but that is not as common but does happen.
Click to expand...
If the spark tester shows loss of spark at the 20 minute mark…what does that mean?


#5

ILENGINE

ILENGINE

PamG said:
If the spark tester shows loss of spark at the 20 minute mark…what does that mean?
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That basically confirms that the ignition module is heat failing. And would require the replacement of the ignition module


#6

PamG

PamG

Ok thanks.


#7

sgkent

sgkent

or ignition switch. get the VOM out and look for where the voltage disappears


#8

PamG

PamG

You mean a multimeter? Not sure what a VOM is…..


#9

ILENGINE

ILENGINE

PamG said:
You mean a multimeter? Not sure what a VOM is…..
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VOM=Volt Ohm Meter aka multimeter


#10

S

slomo

My first thought is trash in the fuel tank. Might flush it out like new. Blow out with compressed air confirming she is spotless. As Bertsmobile1 said, there is clean and there is CLEAN.

New fuel lines might be called for. They deteriorate internally and can block flow. Probably a new fuel filter while you are there. Freshen up the ol' girl.


#11

PamG

PamG

ILENGINE said:
VOM=Volt Ohm Meter aka multimeter
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Ok so weird thing…just now was able to mow my complete lawn non stop! It’s much cooler today too, but the engine still gets hot.


#12

PamG

PamG

slomo said:
My first thought is trash in the fuel tank. Might flush it out like new. Blow out with compressed air confirming she is spotless. As Bertsmobile1 said, there is clean and there is CLEAN.

New fuel lines might be called for. They deteriorate internally and can block flow. Probably a new fuel filter while you are there. Freshen up the ol' girl.
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Awesome! Just figured out how to pull off the cover, so that’s something I’ll look into!


#13

S

slomo

PamG said:
Awesome! Just figured out how to pull off the cover, so that’s something I’ll look into!
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And clean the cooling fins and block like a new one.


#14

PamG

PamG

slomo said:
And clean the cooling fins and block like a new one.
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Any suggestions on what to use to clean them? I have something called “purple power” that’s basically a degreaser…would that work?

Now I just need to find the heat shield…figuring once I remove the cover it should be near the muffler?


#15

S

slomo

PamG said:
Any suggestions on what to use to clean them? I have something called “purple power” that’s basically a degreaser…would that work?

Now I just need to find the heat shield…figuring once I remove the cover it should be near the muffler?
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Brush off the bulk. Compressed air, scrub brushes and degreaser as you like. You will see ribbed cooling fins that need cleaned. Search youtube on cleaning mower cooling fins. Lots of videos on this critical yearly maintenance step. This is for ALL small engines that are air cooled. Trimmers, blowers and mowers..... Clean the engine block like new. Below is a youtube link giving you an idea.





#16

PamG

PamG

slomo said:
Brush off the bulk. Compressed air, scrub brushes and degreaser as you like. You will see ribbed cooling fins that need cleaned. Search youtube on cleaning mower cooling fins. Lots of videos on this critical yearly maintenance step. This is for ALL small engines that are air cooled. Trimmers, blowers and mowers..... Clean the engine block like new. Below is a youtube link giving you an idea.



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Got down to the fins. There wasn’t much there except closer to the carburetor…tried my best but I don’t have compressed air available. Can I get this area wet with degreaser?

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#17

S

slomo

PamG said:
Got down to the fins. There wasn’t much there except closer to the carburetor…tried my best but I don’t have compressed air available. Can I get this area wet with degreaser?
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That breather cover with the black hose coming out. You see the oil? You have a small leak there. I would say fix the oil leak first. Then scrub away with degreaser and water.

It's not the area but the slight oil leak. Not a huge deal.......


#18

PamG

PamG

slomo said:
That breather cover with the black hose coming out. You see the oil? You have a small leak there. I would say fix the oil leak first. Then scrub away with degreaser and water.

It's not the area but the slight oil leak. Not a huge deal.......
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Do you mean this circled area? I don’t want to assume what you’re referring to…clearly there’s a gasket under that connection…so replace that gasket?

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#19

PamG

PamG

slomo said:
That breather cover with the black hose coming out. You see the oil? You have a small leak there. I would say fix the oil leak first. Then scrub away with degreaser and water.

It's not the area but the slight oil leak. Not a huge deal.......
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And does this thing look normal to you? I have no idea what it is…

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#20

S

slomo

Dirty starter motor.


#21

S

slomo

PamG said:
Do you mean this circled area? I don’t want to assume what you’re referring to…clearly there’s a gasket under that connection…so replace that gasket?
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New gasket or breather with gasket time, yes.


#22

PamG

PamG

slomo said:
New gasket or breather with gasket time, yes.
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I’ve now looked and there are thousands of breather tubes on the B&S parts site and nothing comes up for breather gasket…any suggestions on where to find it?


#23

ILENGINE

ILENGINE

PamG said:
I’ve now looked and there are thousands of breather tubes on the B&S parts site and nothing comes up for breather gasket…any suggestions on where to find it?
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www.partstree.com

PartsTree - Home of OEM Parts for Outdoor Power Equipment

Parts lookup and repair parts diagrams for outdoor equipment like Toro mowers, Cub Cadet tractors, Husqvarna chainsaws, Echo trimmers, Briggs engines, etc.
www.partstree.com www.partstree.com

Item 9 on this diagram, but be aware this is only used before code date 07071900. After that date it uses RTV sealant.


#24

A

Auto Doc's

It will need a new starter gear soon; the top edge of the gear is banged up from years of use.
PamG said:
Got down to the fins. There wasn’t much there except closer to the carburetor…tried my best but I don’t have compressed air available. Can I get this area wet with degreaser?
Click to expand...
I recommend you get a can of brake cleaner and spray it, let it sit a couple of minutes and repeat the process until clean. It dries fairly quick and will not cause problems later. The gasket looks like it has been seeping at the breather. Try to snug the screws a little. If it is still doing it later on, then replace the gasket.


#25

9

90210

PamG said:
This engine is on a craftsman riding mower and will only run for 20 minutes from cold, and then 15 minutes after a 20 minute cooldown. Heat seems to be the issue. Have checked oil, airfilter, cap, plug and changed away from ethanol gas. It literally just dies…no rough running at any time. Someone on another forum suggested it could be the ignition going to open circuit when getting hot. Any suggestions?
Click to expand...
YouTube Taryl Fixes all he recently did a video on a mow that was doing that ….
PamG said:
This engine is on a craftsman riding mower and will only run for 20 minutes from cold, and then 15 minutes after a 20 minute cooldown. Heat seems to be the issue. Have checked oil, airfilter, cap, plug and changed away from ethanol gas. It literally just dies…no rough running at any time. Someone on another forum suggested it could be the ignition going to open circuit when getting hot. Any suggestions?
Click to expand...


#26

R

RevB

PamG said:
If the spark tester shows loss of spark at the 20 minute mark…what does that mean?
Click to expand...
Coil replacement. If needed.....
1000013134.png


#27

woodstover

woodstover

Auto Doc's said:
It will need a new starter gear soon; the top edge of the gear is banged up from years of use.

I recommend you get a can of brake cleaner and spray it, let it sit a couple of minutes and repeat the process until clean. It dries fairly quick and will not cause problems later. The gasket looks like it has been seeping at the breather. Try to snug the screws a little. If it is still doing it later on, then replace the gasket.
Click to expand...
Can that gear be flipped over or does it only go on one way? Just curious.


#28

A

Auto Doc's

Hello woodstover,

Sorry, the gear cannot be flipped. If you replace it place a mark with paint or nail polish on it to make sure of the direction. Most are flat on one side but have a recess cutout on the other side.


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