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Purchase a 10yr old MTD mower with a Briggs & Stratton 4.5hp at a yard sale. Owner was not certain if it would run but I did manage to get it to fire with a few shots of carb cleaner in the carburetor. Decided to clean it up with a good gas tank cleaning, new primer bulb, adjusted governor speed, blade sharpened, carb cleaning (replaced diaphragm), oil change and spark plug renewal, and finally - cleaned/oiled the air filter. Reassembled and filled the gas tank. It started on the 2nd pull and off I go cutting the grass. Ten minutes later the revs dropped off as the engine struggled - then quit. I could not get it going. I performed the following checks:

- check for spark: ok
- check oil level: ok
- check fuel level: full
- checked the kill switch/brake mechanism: not familiar with this but all seemed well

After fiddling around I managed to get it going another 10+ minutes of grass cutting and the same thing happened again. Revs dropped and quit. Acts like it runs out of gas in spite of the tank being full. Did notice the spring ring inside the rubber spark plug boot was broken so it may be a little loose on the spark plug. So I used pliers to squeeze it onto the spark plug. Got it going again but the same issue occurred. I'm at a loss as to what is wrong. Has anyone else experienced such? Very frustrated.

Sure does sound like it's fuel starvation.

Let it set for a little while.

Leave the gas cap loose so air can replace the gas drawn from the tank.

Restart and see what happens.

Thanks for the advice. I tried it with a loosened gas cap after sitting. it started again and ran for awhile but conked out again. I switched carb/gas tank assemblies with a similar mower that works and still no luck. Wondering if the coil may be defective?


B & S engine details:
Model Type Code
10T502-0457-B1 07032954



p.s.
Forgot to mention that when I took the cowling off after purchasing there was a rodent nest inside. Think I better investigate again for any wires which may have been chewed on.

In your first post, you said, "--check for spark. OK."

Did you do that check right after it quit running?

No, I did not think to as I was focusing on a fuel issue. Next time it conks out I will check for spark immediately.

I'm thinking either ignition coil or a sticking valve.

cpurvis said:

Sure does sound like it's fuel starvation.

Let it set for a little while.

Leave the gas cap loose so air can replace the gas drawn from the tank.

Restart and see what happens.

Click to expand...

i did that restarted and stoped again

When it stops give it a squirt of starter fluid or carb cleaner down the carb.
If it fires up & runs till it burns off the spray then you have a fuel supply problem.
Get an inline spark tester install that and go mow
When it stops have a quick look at the tester when cranking
No spark = ignition problem
spark = fuel / valve problem.

I am definitely in the fuel supply category.

As recently as of last summer (August of 2018) I had already completed the following:

• replaced the starter solenoid (and added rock-solid ground wire),
• replaced the entire carburetor (this one had a backfire inhibitor solenoid built-in; luckily my existing electrical harness had a positive wire sitting nearby unused, just had to create a ground wire),
• and lastly replaced the battery.

So Saturday I pulled the tractor out of the shed, cleaned it off of debris, filled the tank with gas and "Mechanic in a bottle" additive, topped-off the oil, cleaned all the primary electrical connections with a wire brush, and checked the air filter (already clean). Before replacing the air filter, I poured a few drops of gas into the throat of the carb to prime the starting process.

Then I started the mower: It took a few seconds of cranking but it started and ran clean. Continued to run clean while I cleared the yard of obstancles (pulled a hose out of the way).

After it was warmed-up, I was able to clear about six lengths of the yard, going very slowly because the grass was taller than I would have liked. After an hour I had cleared a swath equal to about a quarter of the total yard, so I disengaged the blades and drove up to the house to get some water. Sadly, about halfway there the engine started to sputter and then died.

I can start it relatively easily (starts after 10 seconds of cranking), and then it sounds perfectly ok to me, and continues to run for about 30 seconds to a minute, but somewhere in there it will just sputter and die. If I pour a bit of gas into the throat of the plastic assembly in front of the carb when it starts to die, it'll continue to run further, then die when it burns through the remaining fuel. It dies whether or not the blades are engaged, and whether or not the gears are active.

Any other suggestions before I pull the carburetor off and tear it apart to inspect it further?

-David

Dave,
Do not know why you tacked this post onto an old thread but the fuel test proves you have a fuel supply problem.
Can be anywhere from the tank cap through to the carb.
Start by loosening the tank cap the instant the engine stops.
If you hear it suck as the cap is unscrewed the the cap is bad.
If the cap is the only problem then it should run fine if the cap is loose.

Bertsmobile1,

I thought it best to continue the thread since I was actually having the same problem as the OP, and there did not seem to be a solution to this thread.

I apologize, but I already tried the cap test and it did not start to run better when the cap was removed, nor did I hear a sucking sound while loosening the cap, but suppose that aspect is arguable since the sound of the engine might have drowned -out that particular sound out.

-David

People panic, join the forum, find the problem then never bother to come back with a "problem solved" post

It is a process of elimination.
Grab a can of starter fluid and an inline red spark tester.
Fit the spark tester then go mow.
When the engine starts to die have a look at the tester.
If the tester continues to flash all the way to the bitter end and then flashes strongly when you are cranking the engine and it is not starting you have then eliminated the coil & spark plug lead.
\

The engine can stop for a few reasons .
Not enough fuel or too much fuel is one of them.

SO when it stops give the carb a SHORT shot of starter fluid.
If it fires right up then you have a fuel starvation problem.

If it does not start then you have an excess fuel situation

And of course do all of this with a nice new properly gapped spark plug.

If your engine has an oil level sensor, make sure that the oil is full to the top.\
Had a customer who perpetually runs the engine with low oil ( never checks it before he starts to mow ).
After about 10 minutes or so, a lot of the oil that was in the sump when he started is distributed all around the engine.
The oil level in the sump drope below the preset cut off ( appear to be a bit too high ) and the mower stops dead .
OTOH he pays me $ 30 to turn up, put about a pint of oil in the engine then he carries on mowing to repeat the same in about 2 to 3 months time.

Let us know what happens & we will walk you through what else is needed to be tested.

Continuing to see the problem after only about 30 seconds each time. Pouring more gas into the carb delays the eventual death of the engine.

I'm drawn to an observation by ILENGINE on a different thread about the solenoid on my carb possibly being defective and causing the plunger in the solenoid to close and shut off the fuel supply.

Know of a way to test that possibility? I can't see how to remove the solenoid, but if it is removable and replaceable, I would happily attempt that.

DAMatson said:

Continuing to see the problem after only about 30 seconds each time. Pouring more gas into the carb delays the eventual death of the engine.

I'm drawn to an observation by ILENGINE on a different thread about the solenoid on my carb possibly being defective and causing the plunger in the solenoid to close and shut off the fuel supply.

Know of a way to test that possibility? I can't see how to remove the solenoid, but if it is removable and replaceable, I would happily attempt that.

Click to expand...

The solenoid unscrews. If i remember correctly uses a 1/2 wrench. maybe have to be ground slightly thinner than normal to reach in and get on the two flat surfaces.

Yeah, it'll be tough for sure to get in there with a wrench, but before I started that angle of attack I've tried looking for a replacement solenoid, but came up empty handed.

Alright, I had been suspecting that the Fuel Solenoid as the problem, so I removed the bowl with the solenoid and replaced it with the old bowl with a straight screw-on plug. I used the NEW main fuel tube jet because it had a newer o-ring on it, and the bowl-to-carb gasket is brand new as well.

While it wouldn't start unless I primed the carb, the mower started, ran fine for more than a minute (a record for me, since it usually dies after 30 seconds), so now I'm certain the original problem was due to the Fuel Solenoid. I continued to let it sit running for about 4 or 5 minutes, while I cleaned up the mess of tools. I then decided to take advantage of the opportunity since it was mostly sunny out to actually get some mowing done.

Got about halfway across the yard when the engine started to sputter again, so I took the burden off the engine by coming to a stop, putting the gear in Neutral, and disengaging the blades. Immediately the engine perked right back up for about 10 seconds, after which it sputtered yet again and died. This was after continous good running for 7 minutes, the last two under load (in gear, and blades engaged). Now I'm really confused.

It cranks ok, but the engine still won't start-up when turning the key still, so I suspect there is still a clogged port in the original old bowl.

So I prime the carb and it starts and runs fine for a minute and thirty-seconds. This happens repeatedly.

Since the problem is now effectively worse, I took my old bowl off the new Carb again, then pulled the Fuel Solenoid off of my new Bowl and replaced it with the plain threaded plug from the old carb and re-installed the new Bowl back onto the new Carb. Still using the new Gasket and Fuel tube. Effectively, the entire NEW Carb is now installed back in, except that the Fuel Solenoid has been removed and replaced with a plain threaded plug.

It now starts right-up again without needing priming (so that would tend to indicate that my previous thought about the old bowl still having a plugged port is likely correct), but still dies after 1 minute to 2 minutes. So now I'm considering that when I replaced the bowl these last two times, maybe I mucked something up.

The first question I have is: the main fuel tube has a series of 3 micro holes (2 grouped together near the o-ring, and a 3rd hole about the middle of the tube) on two sides directly across from each other. Do those have to be aligned in a certain direction when placed in the carb bowl? I had thought that I had re-aligned them exactly how I found them on the NEW Bowl when I pulled it out originally, but maybe I got that alignment wrong.

Thoughts?

Check the vent on your gas cap. Under load the engine uses a lot more fuel. If fuel can't get to the carb, it sputters and dies. Also, fuel filter if it has one.

Thank you cpurvis!

The cap itself was confirmed as not being the cause a lot earlier when I pulled the cap off before the sputtering and eventual death of the engine.

However, your suggestion led me to investigate the fuel-line where I found a plastic curled burr in the gas-tank nozzle feed that the fuel line plugs into. The curl of this burr had hung-on to some gunk and was acting like a slinky with a movable dam that would uncoil far enough and allow some fuel through, but would apparently (at some point) coil back up and cut off the flow of gas. I can only presume that this burr originated from the milling of the fuel line plug on the gas tank.

I drained and removed the tank, and that's when I found and removed the coiled burr and the attached gunk. The hoses from the tank to the carb were all original, so I replaced them all as well, replaced the inline fuel filter, and now everything is working fine. I was even able to get in some mowing time before the mosquitos came out.

So the Fuel Solenoid definitely failed and was my primary/original problem. The plastic burr with gunk on it was a secondary issue that only served to create some additional head scratching. Thank you all for the contributions!

Good! Glad you got that resolved!

cpurvis said:

Good! Glad you got that resolved!

Click to expand...

If popping some more fuel down the carb throat perks up the engine then you still have a fuel problem.
Remove the fuel line from the carb and crank the engine.
You should get a strong flow the full diameter of the fuel line if all is well.
I use a 2' length of fuel line on the pump held strait up in the air to access if the pump is working well enough.

Fuel pumps do occasionally go bad and can not supply enough fuel to feed the carb.
Crud also builds up in the fuel tank and blocks off the outlet.
I check for that by rigging up a temporary fuel tank.
Something about a quart is good if you want to give that a try.

Hi BertsMobile!

After removing the plastic burr (and it's attached gunk), everything is working fine now. Just wanted to provide the happy ending that you guys deserve, but which so often go unanswered/unresolved, etc. Thank you again!

So was it a casting flash in the fuel tank outlet and a plug of debris in the fuel tank hanging on it ?

bertsmobile1 said:

So was it a casting flash in the fuel tank outlet and a plug of debris in the fuel tank hanging on it ?

Click to expand...

I had the exact same problem with mine. My BF at the time replaced the coil, the fuel line, the gas cap and after all of that, it was the head gasket. In the 10 year old mower I bought new, the head gasket continued to blow over and over the last year. Now the deck is so screwed up and will not stay level, that I have a perfectly good body that has been garage kept, great tires, new transmission and a good motor that I cannot use anymore. Frustrating!!!

You must have a B & S Intek engine.
The head & barrel have a bad habit of warping & burning, in particular between the cylinder & pushrod tube.
I usually stone both when doing a head gasket.
In extreme cases I get Lanni at coppergasketsUS to cut me some 1/16" copper ones.
Just remember they will arrive 1/2 hard so need to be annealed before fitting.

The carburetor, almost always, has some free-floating debris in the bowl intermittently fouling the proper flow. I am afraid you need to tear it down and clean it out.
I have some similar mowers UC-9iOjFuLSRw26Vh-GP7Nwg