4th cylinder still dead!!!!!

envader

Seaman
Joined
Aug 21, 2007
Messages
57
i have checked everything cleaned carbs 3 times, good comp. good spark, fuel, I tried sea foam. Still nothing i took it to the lake this morning and under a load it starts to jug imediatly
 

rickdb1boat

Supreme Mariner
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Jan 23, 2002
Messages
11,195
Re: 4th cylinder still dead!!!!!

Have you done a compression test yet? Could be a weak cylinder. Also, hook a timing light to each wire when the engine is under a load and see if you still have spark..
 

envader

Seaman
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Aug 21, 2007
Messages
57
Re: 4th cylinder still dead!!!!!

yes all cylinders have 120+ i will try a timing light
 

ezeke

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Sep 19, 2003
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12,532
Re: 4th cylinder still dead!!!!!

edit
 
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envader

Seaman
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Aug 21, 2007
Messages
57
Re: 4th cylinder still dead!!!!!

Yes i have tried a diff plug what is helicoil.?
 

ezeke

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Sep 19, 2003
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12,532
Re: 4th cylinder still dead!!!!!

edit
 
Last edited:

Dhadley

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Feb 4, 2001
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16,978
Re: 4th cylinder still dead!!!!!

What motor are we talking about?
 

envader

Seaman
Joined
Aug 21, 2007
Messages
57
Re: 4th cylinder still dead!!!!!

no there is no helicoil. it is a 1975 johnson 135hp 4v
 

Dhadley

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Feb 4, 2001
Messages
16,978
Re: 4th cylinder still dead!!!!!

If you have spark but the plug is still wet, it may be a fuel pump problem. The pulse line is connested to #4. If the diaphram is leaking it will flood #4.
 

envader

Seaman
Joined
Aug 21, 2007
Messages
57
Re: 4th cylinder still dead!!!!!

the plug is dry all the time . could it be a ring problem
 

Dhadley

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Feb 4, 2001
Messages
16,978
Re: 4th cylinder still dead!!!!!

If the plug is dry all the time -- like new & dry -- then it's a fuel delivery problem. Either fuel isn't getting thru the carb or the piston is pulling air from somewhere rather than pulling fuel.
 

envader

Seaman
Joined
Aug 21, 2007
Messages
57
Re: 4th cylinder still dead!!!!!

Replaced intake gasket reeds look to be in good shape i believe the fuel delivery is good what could the source of air be could the head be cracked
 
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