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Briggs 4.5hp - hard to start when hot #4543360
10/14/17 04:35 PM
10/14/17 04:35 PM
Joined: Jun 2013
Posts: 701
Northeast
Finz Offline OP
Finz  Offline OP
Joined: Jun 2013
Posts: 701
Northeast
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
Re: Briggs 4.5hp - hard to start when hot [Re: Finz] #4543371
10/14/17 04:52 PM
10/14/17 04:52 PM
Joined: Feb 2015
Posts: 2,203
Slovenia EU
Kamele0N Offline
Kamele0N  Offline
Joined: Feb 2015
Posts: 2,203
Slovenia EU
Did you check a spark when hot? Maybe its worn out CDI unit or condenser...

Last edited by Kamele0N; 10/14/17 04:53 PM.

2011 Hyundai i30 1.4 CVVT Shell Helix Ultra 5w40
1997 Toyota Landcruiser KZJ95 3.0 TD Shell Rimula R6M 10w40
Re: Briggs 4.5hp - hard to start when hot [Re: Finz] #4543373
10/14/17 04:54 PM
10/14/17 04:54 PM
Joined: Oct 2009
Posts: 3,239
Wet side WA
JohnnyJohnson Online content
JohnnyJohnson  Online Content
Joined: Oct 2009
Posts: 3,239
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.

Last edited by JohnnyJohnson; 10/14/17 04:54 PM.

2004 Corolla 124900
Out: VML 5w-30 TG4967 OCI 5007 Miles
In: EDGE EP 5W-30 Bosch 3311 122537 7-18-18
2006 Duramax 74277
Out: T6 5W-40 M1-303
In: T6 5W-40 XG9100 74705 4-22-18
Re: Briggs 4.5hp - hard to start when hot [Re: Finz] #4543390
10/14/17 05:23 PM
10/14/17 05:23 PM
Joined: Sep 2004
Posts: 7,533
Marshfield , MA
andyd Offline
andyd  Offline
Joined: Sep 2004
Posts: 7,533
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


'16 Camry LE STP synth 0w20 and STP filter. the Fridge

1994 Ranger ,the Rat, 5w30 dino, STP filter

'16 Camry SE, Valvoline HM 0w20 and OEM filter
Thick oil is better grin2
Re: Briggs 4.5hp - hard to start when hot [Re: Finz] #4543399
10/14/17 05:32 PM
10/14/17 05:32 PM
Joined: Jun 2013
Posts: 701
Northeast
Finz Offline OP
Finz  Offline OP
Joined: Jun 2013
Posts: 701
Northeast
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


God Bless America
Re: Briggs 4.5hp - hard to start when hot [Re: Finz] #4543423
10/14/17 06:01 PM
10/14/17 06:01 PM
Joined: Nov 2009
Posts: 132
oklahoma
hyperscion Offline
hyperscion  Offline
Joined: Nov 2009
Posts: 132
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

Re: Briggs 4.5hp - hard to start when hot [Re: Finz] #4543428
10/14/17 06:12 PM
10/14/17 06:12 PM
Joined: Jan 2007
Posts: 17,501
Clovis, CA
Merkava_4 Offline
Merkava_4  Offline
Joined: Jan 2007
Posts: 17,501
Clovis, CA
What are the engine numbers Finz ?

Re: Briggs 4.5hp - hard to start when hot [Re: Finz] #4543435
10/14/17 06:21 PM
10/14/17 06:21 PM
Joined: Sep 2015
Posts: 1,531
USA
mk378 Online content
mk378  Online Content
Joined: Sep 2015
Posts: 1,531
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.

Re: Briggs 4.5hp - hard to start when hot [Re: Merkava_4] #4543455
10/14/17 06:42 PM
10/14/17 06:42 PM
Joined: Jun 2013
Posts: 701
Northeast
Finz Offline OP
Finz  Offline OP
Joined: Jun 2013
Posts: 701
Northeast
Originally Posted By: Merkava_4
What are the engine numbers Finz ?


12H802-1777-D1 02092557


God Bless America
Re: Briggs 4.5hp - hard to start when hot [Re: mk378] #4543459
10/14/17 06:46 PM
10/14/17 06:46 PM
Joined: Jun 2013
Posts: 701
Northeast
Finz Offline OP
Finz  Offline OP
Joined: Jun 2013
Posts: 701
Northeast
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
Re: Briggs 4.5hp - hard to start when hot [Re: hyperscion] #4543470
10/14/17 06:53 PM
10/14/17 06:53 PM
Joined: Jun 2013
Posts: 701
Northeast
Finz Offline OP
Finz  Offline OP
Joined: Jun 2013
Posts: 701
Northeast
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
Re: Briggs 4.5hp - hard to start when hot [Re: Finz] #4543564
10/14/17 08:42 PM
10/14/17 08:42 PM
Joined: Sep 2014
Posts: 1,447
Toronto Canada
WobblyElvis Offline
WobblyElvis  Offline
Joined: Sep 2014
Posts: 1,447
Toronto Canada
Re torque the head bolts and check for loose bolts at the intake manifold.

Re: Briggs 4.5hp - hard to start when hot [Re: Finz] #4543621
10/14/17 10:06 PM
10/14/17 10:06 PM
Joined: Apr 2009
Posts: 2,933
Canada
boraticus Offline
boraticus  Offline
Joined: Apr 2009
Posts: 2,933
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.

Re: Briggs 4.5hp - hard to start when hot [Re: Finz] #4543662
10/14/17 11:57 PM
10/14/17 11:57 PM
Joined: Mar 2008
Posts: 5,841
South Florida
bubbatime Offline
bubbatime  Offline
Joined: Mar 2008
Posts: 5,841
South Florida
Drop the spark plug gap from 0.030 to 0.020. If that works your coil is going out.


17 Chrysler Pacifica Mobil 1 5W30
13 Yamaha XT250 Valv MC 10W40
12 Suzuki S40 Rotella 15W40
10 Acura TSX 2.4 PZL Plat 5W30
06 GMC Sierra Nextgen 10W30


Re: Briggs 4.5hp - hard to start when hot [Re: Finz] #4543674
10/15/17 01:00 AM
10/15/17 01:00 AM
Joined: Jan 2007
Posts: 17,501
Clovis, CA
Merkava_4 Offline
Merkava_4  Offline
Joined: Jan 2007
Posts: 17,501
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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