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#4543360 - 10/14/17 04:35 PM Briggs 4.5hp - hard to start when hot
Finz Offline


Registered: 06/06/13
Posts: 692
Loc: Northern NJ
Read a post on here weeks ago (about generators?.) and the poster had the same symptoms and someone mentioned the cause but I'll be darned if I can find it again

Have a Yard Machine lawn vacuum with a 4.5hp briggs engine

Starts on 1st - 3rd pull when I roll it out of the shed.

Once hot, however, it refuses to catch ( like right now) so I have to take a break and wait for it to cool down.

Now there IS an interlock on the bag which can get finicky but I'm aware of this and it's not the cause for the inability to start.

Choke on... choke off... partial throttle... full throttle... has no impact

One issue that could be relevant: the gas cap allows gas to weep out of the Neck of the filler. Just replaced the cap and it still weeps.... pretty sure I picked up the proper replacement. Actually 95% sure I ordered the right replacement although not an OEM

Anyone have any thoughts as to why this happens...?

Thank you

--bob
_________________________
God Bless America... We really need it about now

06 Odyssey
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11 Civic 1.8 sedan
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#4543371 - 10/14/17 04:52 PM Re: Briggs 4.5hp - hard to start when hot [Re: Finz]
Kamele0N Offline


Registered: 02/09/15
Posts: 2041
Loc: Slovenia
Did you check a spark when hot? Maybe its worn out CDI unit or condenser...


Edited by Kamele0N (10/14/17 04:53 PM)
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#4543373 - 10/14/17 04:54 PM Re: Briggs 4.5hp - hard to start when hot [Re: Finz]
JohnnyJohnson Online   content


Registered: 10/22/09
Posts: 2745
Loc: Wet side WA
Originally Posted By: Finz
Read a post on here weeks ago (about generators?.) and the poster had the same symptoms and someone mentioned the cause but I'll be darned if I can find it again

Have a Yard Machine lawn vacuum with a 4.5hp briggs engine

Starts on 1st - 3rd pull when I roll it out of the shed.

Once hot, however, it refuses to catch ( like right now) so I have to take a break and wait for it to cool down.

Now there IS an interlock on the bag which can get finicky but I'm aware of this and it's not the cause for the inability to start.

Choke on... choke off... partial throttle... full throttle... has no impact

One issue that could be relevant: the gas cap allows gas to weep out of the Neck of the filler. Just replaced the cap and it still weeps.... pretty sure I picked up the proper replacement. Actually 95% sure I ordered the right replacement although not an OEM

Anyone have any thoughts as to why this happens...?

Thank you

--bob


It is always great on a hot summer day to have a good reason for that next cold beer while you wait for it to cool off.


Edited by JohnnyJohnson (10/14/17 04:54 PM)
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#4543390 - 10/14/17 05:23 PM Re: Briggs 4.5hp - hard to start when hot [Re: Finz]
andyd Online   content


Registered: 09/25/04
Posts: 7149
Loc: Marshfield , MA
I wonder if the gas in the final stages of mixing in a hot intake evaporates and now you don't have the stuff (vacuum) to start the process. Just for grins check the carb/manifold/block screws
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#4543399 - 10/14/17 05:32 PM Re: Briggs 4.5hp - hard to start when hot [Re: Finz]
Finz Offline


Registered: 06/06/13
Posts: 692
Loc: Northern NJ
I'll check for spark... hadn't thought of that

I KNEW I was setting myself up for the "taking a break" comment smile

I'll take the carb off and reassemble... maybe just look into replacement as it's 15 years old. Be surprised if more than $20

Thanks all
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#4543423 - 10/14/17 06:01 PM Re: Briggs 4.5hp - hard to start when hot [Re: Finz]
hyperscion Offline


Registered: 11/14/09
Posts: 132
Loc: oklahoma
ok. dad same problem with a a new mower and i have had this with honda and B&S. We mow ALOT... leave about 1 inch of air space in gas tank when filling up to mow. lube spray all throttle linkinge from handle to engine. I use schaeffer's NEUTRA in all our gas cans.... it cleans carbs,stabilizes gas, and is a fuel lubricator,,,GREAT STUFF. We also only use redline oil or amsoil oil,,0w30. It made a huge diff in our seven push mowers and 2 drivers.
When shut down hot, I think some of the mowers got a little flooded. but not anymore.
goodluck

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#4543428 - 10/14/17 06:12 PM Re: Briggs 4.5hp - hard to start when hot [Re: Finz]
Merkava_4 Offline


Registered: 01/30/07
Posts: 17501
Loc: Clovis, CA
What are the engine numbers Finz ?

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#4543435 - 10/14/17 06:21 PM Re: Briggs 4.5hp - hard to start when hot [Re: Finz]
mk378 Offline


Registered: 09/27/15
Posts: 1420
Loc: USA
If you haven't been keeping the cooling system clean, it could be overheating. Pull the air shroud and clean the cylinder fins etc.

This does sound a lot like a coil that stops working due to heat soak. Spark test would tell. You can disconnect any kill switches, oil sensors, etc from the coil kill wire to test only the coil.

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#4543455 - 10/14/17 06:42 PM Re: Briggs 4.5hp - hard to start when hot [Re: Merkava_4]
Finz Offline


Registered: 06/06/13
Posts: 692
Loc: Northern NJ
Originally Posted By: Merkava_4
What are the engine numbers Finz ?


12H802-1777-D1 02092557
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God Bless America... We really need it about now

06 Odyssey
06 Civic coupe
05 Accord 2.4 sedan
11 Civic 1.8 sedan
18 Civic 1.5l Turbo sedan

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#4543459 - 10/14/17 06:46 PM Re: Briggs 4.5hp - hard to start when hot [Re: mk378]
Finz Offline


Registered: 06/06/13
Posts: 692
Loc: Northern NJ
Originally Posted By: mk378
If you haven't been keeping the cooling system clean, it could be overheating. Pull the air shroud and clean the cylinder fins etc.

This does sound a lot like a coil that stops working due to heat soak. Spark test would tell. You can disconnect any kill switches, oil sensors, etc from the coil kill wire to test only the coil.


I hear what you're saying but I don't have the first clue as to how check that. Cleaning out fins... sure. Check for spark,...? Pull plug and pull cord with plug grounded against engine....?

But the rest? I'll try to find a YouTube or something

Thank you
_________________________
God Bless America... We really need it about now

06 Odyssey
06 Civic coupe
05 Accord 2.4 sedan
11 Civic 1.8 sedan
18 Civic 1.5l Turbo sedan

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#4543470 - 10/14/17 06:53 PM Re: Briggs 4.5hp - hard to start when hot [Re: hyperscion]
Finz Offline


Registered: 06/06/13
Posts: 692
Loc: Northern NJ
Originally Posted By: hyperscion
ok. dad same problem with a a new mower and i have had this with honda and B&S. We mow ALOT... leave about 1 inch of air space in gas tank when filling up to mow. lube spray all throttle linkinge from handle to engine. I use schaeffer's NEUTRA in all our gas cans.... it cleans carbs,stabilizes gas, and is a fuel lubricator,,,GREAT STUFF. We also only use redline oil or amsoil oil,,0w30. It made a huge diff in our seven push mowers and 2 drivers.
When shut down hot, I think some of the mowers got a little flooded. but not anymore.
goodluck


Thank you... all gas is already treated with Stabil and a splash of MMO and" because of the stupid leaky gas caps, I fill the tank halfway or so

I'll check out Neutra.... never heard of it

After reading that Generator post - which was really a discussion about oil - I replaced the oil with Rotella T6. 5w-40
_________________________
God Bless America... We really need it about now

06 Odyssey
06 Civic coupe
05 Accord 2.4 sedan
11 Civic 1.8 sedan
18 Civic 1.5l Turbo sedan

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#4543564 - 10/14/17 08:42 PM Re: Briggs 4.5hp - hard to start when hot [Re: Finz]
WobblyElvis Offline


Registered: 09/23/14
Posts: 1345
Loc: Toronto Canada
Re torque the head bolts and check for loose bolts at the intake manifold.

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#4543621 - 10/14/17 10:06 PM Re: Briggs 4.5hp - hard to start when hot [Re: Finz]
boraticus Offline


Registered: 04/19/09
Posts: 2905
Loc: Canada
I'd guess it's electrics as mentioned in some of the above posts. Failing that, it could possibly be tight valves. When the engine heats to the point of metal expansion, the valves may not be closing sufficiently to create necessary compression. Thus reluctance to start.

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#4543662 - 10/14/17 11:57 PM Re: Briggs 4.5hp - hard to start when hot [Re: Finz]
bubbatime Offline


Registered: 03/18/08
Posts: 5627
Loc: South Florida
Drop the spark plug gap from 0.030 to 0.020. If that works your coil is going out.
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#4543674 - 10/15/17 01:00 AM Re: Briggs 4.5hp - hard to start when hot [Re: Finz]
Merkava_4 Offline


Registered: 01/30/07
Posts: 17501
Loc: Clovis, CA
Originally Posted By: Finz
12H802-1777-D1 02092557


Those last set of numbers, the code number, tells me you have a carburetor with an automatic choke. The thermostat is probably not pulling the choke off. With the choke still on and the engine hot, it's not going to start. Replace thermostat 790830 and exhaust gasket 691881.

You can verify by pulling the air cleaner off. If the choke plate is still closed when the engine is hot, that's your problem. That engine came with 3 different carburetors depending on the date code: Primer Carb, Manual Choke Carb, and Auto Choke Carb. The automatic choke carb was for date codes before 05091900.

Personally, I'd convert it over to a primer carb system.

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