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Portable generator engine help.


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Find some kind of squirt can bottle that will tolerate gasoline and fill it with gasoline.  Pull the air filter off and what ever else you need to so you can squirt gasoline into the carb. When the engine wants to die, see if you can get it to run good on “Mexican fuel injection”. If it will, you have a carb problem. If there is very little response to it, you have an ignition failure. 

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5 minutes ago, yellowrosefarm said:

Carb main jet plugged, or an outside chance the hose from the tank to the carb is partially plugged or has come apart inside. Does that plastic tank have a screen inside above the fuel outlet?

No screens, no visible crap when the carb has been off, that doesn’t mean something gummy isn’t clogging up the works. 

 

2 minutes ago, BoilerRed said:

Fuel line breaking down and dumping debris into the carb?

I suppose it is conceivable.  

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2 minutes ago, vtfireman85 said:

No screens, no visible crap when the carb has been off, that doesn’t mean something gummy isn’t clogging up the works. 

 

I suppose it is conceivable.  

Rig up a gallon jug and clear fuel line straight to the carb.  Hang it high to gravity feed.  You will at least eliminate everything upstream of the carb.

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4 minutes ago, Matt Kirsch said:

Burned valve? If it's not fuel and not ignition then it's mechanical. As hot and as lean as it got I would not doubt but it has a burned valve.

With 175 lbs compression? 
i did to a leak down test as well, found nothing. 

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Just now, vtfireman85 said:

With 175 lbs compression? 

I had a Kohler on a Cub Cadet that had good compression cold. It started right up and sounded great, for a couple of minutes. Then it would start breaking up and eventually it would die. You could restart it but it would not stay running. Turned out it had a burned valve that sealed fine until the engine built a little heat.

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3 hours ago, nomorejohndeere said:

crankcase oil fuel tainted?

 

Doesn’t smell like it 

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Stuck valve? Do compression as soon as it quits? May make sense of glowing muffler, I think.

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5 hours ago, nomorejohndeere said:

crankcase oil fuel tainted?

 

 

2 hours ago, vtfireman85 said:

Doesn’t smell like it 

Gasoline in the oil will make an engine run rich if the blowby is routed into the intake tract like the EPA says is should be.  It doesn’t sound like this engine is running rich.  

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Valve that is sticking when it gets heated up?? Does it build up compression once it quits? I know it is difficult to do a compression test quickly but does it crank over differently, quicker or easier? 

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I tripped over this so for the record - something Generac that mightn't apply here

""@Ossqss; have a 20 year old Generac 5000 that started giving me fits. It would fart and wheeze acting like it was having fuel problems. I cleaned the tank and several times cleaned the carburetor. Then noticed that the Idiot light in the on-off switch was cutting off as the engine farted off and after a while got down on my hands and knees and read the little placard there that said that the machine had a low oil ignition cut off. Strange, the dip stick read nearly full. I filled it a bit overfull and Damn ! It ran fine, If it is about 1/8th inch over full.
My guess is the dip stick used is not the correct one and at half level is actually low So that the low level switch is cutting off the ignition.
Bet if you over fill a bit and reconnect that cut off switch your old Generac will run fine…pg."

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I am heading off for a week on Sunday, i am going to revisit this machine upon my return, stay tuned.. 

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Another thought could be a vacuum leak around the base of the carburetor or spacer causing it to run a lean, thereby heating up the heads to the point that a valve dragged. Have you taken a infrared gun and check the temps on the head?

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2 hours ago, busted knuckles said:

best answer yet I think. I have had fine metal or crud stop one from working before.

I have a B&S on a generator with a low oil/chip detector shutoff. A tiny bit of fuzz would shut it down. I put a magnetic drain plug on it and it still wouldn't start one time with an almost undetectable amount of fuzz on it. I check the oil on every fill so that got disconnected.

Chip detectors on lots of helicopter gearboxes have "Zappers" that the pilots can activate to determine if it's just fuzz giving them a chip light or a disaster about to happen. Fuzz get burned off but a piece of gear tooth or bearing won't. A little too sophisticated for a Briggs?.

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What is the valve clearance? Sounds like a decent chance the exhaust valve doesn't have sufficient clearance. When all the parts get to operating temp and have swelled, the valve no longer closes fully. This is a common problem, especially on L head engines. And worse is people chase the carb, adding fuel until the cylinder washes.

Put a load on the engine and listen when it gets to the point where the problem starts. You are listening for a "squeaking" sound in the exhaust pulses. Also, have your compression tester ready to go, do the test when it gets hot.

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8 minutes ago, Cattech said:

What is the valve clearance? Sounds like a decent chance the exhaust valve doesn't have sufficient clearance. When all the parts get to operating temp and have swelled, the valve no longer closes fully. This is a common problem, especially on L head engines. And worse is people chase the carb, adding fuel until the cylinder washes.

Put a load on the engine and listen when it gets to the point where the problem starts. You are listening for a "squeaking" sound in the exhaust pulses. Also, have your compression tester ready to go, do the test when it gets hot.

Wouldn't it be simpler to just readjust the valves, I have never had that happen but as usual you are making good sense.

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20 minutes ago, Cattech said:

What is the valve clearance? Sounds like a decent chance the exhaust valve doesn't have sufficient clearance. When all the parts get to operating temp and have swelled, the valve no longer closes fully. This is a common problem, especially on L head engines. And worse is people chase the carb, adding fuel until the cylinder washes.

Put a load on the engine and listen when it gets to the point where the problem starts. You are listening for a "squeaking" sound in the exhaust pulses. Also, have your compression tester ready to go, do the test when it gets hot.

.003 as per Generac 

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What sort of compression difference should I expect from a hot engine? 

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13 minutes ago, vtfireman85 said:

What sort of compression difference should I expect from a hot engine? 

I wouldn't expect a big change if everything is in good order. < +/- 10%. Idea is not finding a large change.

Also keep in mind, what is a little leakage during a compression check, is a whole lot different when spinning 3600 RPM and the cylinder pressure is well over 500 PSI each firing stroke. So a lack of change doesn't truly mean you have ruled out a problem. 

If your valve clearance is sufficient to spec I may be mistaken. As you mentioned, this thing doesn't have many hours, so seat wear shouldn't be an issue yet, would have to have been tight from new.

Just pointing out a commonly overlooked issue. The glowing muffler is one of the first things I look for if I suspect valve leakage in a small engine.

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16 hours ago, Ian Beale said:

I tripped over this so for the record - something Generac that mightn't apply here

""@Ossqss; have a 20 year old Generac 5000 that started giving me fits. It would fart and wheeze acting like it was having fuel problems. I cleaned the tank and several times cleaned the carburetor. Then noticed that the Idiot light in the on-off switch was cutting off as the engine farted off and after a while got down on my hands and knees and read the little placard there that said that the machine had a low oil ignition cut off. Strange, the dip stick read nearly full. I filled it a bit overfull and Damn ! It ran fine, If it is about 1/8th inch over full.
My guess is the dip stick used is not the correct one and at half level is actually low So that the low level switch is cutting off the ignition.
Bet if you over fill a bit and reconnect that cut off switch your old Generac will run fine…pg."

Further discussion there - apparently those low oil sensors can get bridged by metal dust from engine wear and short out

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2 hours ago, Ian Beale said:

Further discussion there - apparently those low oil sensors can get bridged by metal dust from engine wear and short out

In the case of this one it has a pressure sensor, not a level sensor, using the same 999 engine the LP units do. They can be finicky and problematic, easy enough to jump past and ill try it. I suspect something more sinister, but definitely a good thing to rule out. They seem to jump around between N.O. and N.C pressure switches randomly. Makes it difficult to have the right ones in stock, some are 1/8” some 1/4” thread, some 1 wire, some 2.. it’s annoying.  

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