Author Topic: oil spewing from vacuum fuel pump on kohler 20hp v-twin.  (Read 5441 times)

dmb0702

  • Guest
oil spewing from vacuum fuel pump on kohler 20hp v-twin.
« on: June 09, 2014, 09:56:37 AM »
Hi I have a sears craftsman GT riding mower with the 20hp Kohler engine.  Recently I noticed the engine was laboring while the mower was engaged and the engine seemed to have a hard time continuing to run when going up hill.  I stop the tractor to check the gas and opened the hood to check the plug cables.  On the right hand side where the vacuum fuel pump is, there was oiled sprayed everywhere.  I also checked the oil which was level but grey and smelled of gas.  I went to google and found what I thought to be the problem was a head gasket.  I replaced that this weekend and took the tractor for a ride.  Same problem occured, so this time I wiped up all the oil mess and held a fresh sheet of paper towel over the right side to see if I could see where the oil was coming from.  Once the engine got up to temperature it started sputtering here and there and then started spraying what appears to be oil from the brass breather hole on the vacuum fuel pump.  I should also state I replaced the plugs and changed the oil even though the plugs looked fine.  The combustion chambers on each side of the engine had some black residue but looked the same on each side.  I use a scotch brite pad to clean up as best as I could but some still remained.  I fear that the rings may be bad on this engine and I don't have the skill or tools to replace them.  I bought this tractor used 6 years ago and it has worked great for me until this season.  Always change the oil at the beginning of every summer. Any suggestions you would have would be appreciated. 

smallengineshop

  • Sr. Member
  • ****
  • Posts: 264
Re: oil spewing from vacuum fuel pump on kohler 20hp v-twin.
« Reply #1 on: June 09, 2014, 09:44:28 PM »
It sounds like something is causing to much crankcase pressure to develop in your engine and the excessive pressure is pushing the oil out. Some likely causes could be a plugged hose, bad breather valve or blown head gasket.
John 3:16 For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life.

dmb0702

  • Guest
Re: oil spewing from vacuum fuel pump on kohler 20hp v-twin.
« Reply #2 on: June 10, 2014, 08:51:01 AM »
I replaced both head gaskets this past weekend and still have the problem.  I will check the hoses, but is it possible the vacuum fuel pump is bad? 

smallengineshop

  • Sr. Member
  • ****
  • Posts: 264
Re: oil spewing from vacuum fuel pump on kohler 20hp v-twin.
« Reply #3 on: June 11, 2014, 06:48:31 PM »
Have you tried doing a leak down test to make sure the top-end (piston, rings, cylinder, valves) is in good working order?
John 3:16 For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life.

dmb0702

  • Guest
Re: oil spewing from vacuum fuel pump on kohler 20hp v-twin.
« Reply #4 on: June 12, 2014, 01:26:45 PM »
I have not, I have read about leak down tests but don't know how to preform one.  It's not in my owners manual.

smallengineshop

  • Sr. Member
  • ****
  • Posts: 264
Re: oil spewing from vacuum fuel pump on kohler 20hp v-twin.
« Reply #5 on: June 14, 2014, 02:02:48 AM »
If you go to the Kohler engine website you can download the manual for your engine. Is your engine the CV20? If it is, than here is the link for the manual:

Kohler Engine CV20 Service Repair Manual

If your engine is not the CV20, than go here to find your engine and download the manual:

Find Kohler Engine Service Manual

In the manual it talks about performing a leak down test, and there are video's on YouTube that will show you how to perform the test. It sounds like you might have excessive gases leaking past the piston and piston rings, which is called Blow-By. Some blow-by is normal especially when the engine is cold, but when it becomes excessive, than the crankcase pressure will increase forcing oil out of the engine. Excessive blow-by will also explain why you are smelling gas in the oil and why your tractor has lost power.

I am working on a video where I talk about crankcase pressure and blow-by. I should have it uploaded sometime this weekend.
John 3:16 For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life.

dmb0702

  • Guest
Re: oil spewing from vacuum fuel pump on kohler 20hp v-twin.
« Reply #6 on: June 16, 2014, 09:52:23 AM »
I found that the hose coming from the breather valve was crimped between the air filter plate and the engine.  The previous owner must have replaced the hose with just a piece of Napa fuel line its to large for the opening.  That stopped the oil spew when I fixed it.  Now my engine is still running rich.  I am going to try and adjust the carburetor but think I should clean it at the same time, what are your thoughts? I have a CV675 engine and can't find the service manual for it on Kohlers site.  Do they have a different number that is the same as CV675?  Thank you so much for your help btw, you were right on with the hose being blocked.

smallengineshop

  • Sr. Member
  • ****
  • Posts: 264
Re: oil spewing from vacuum fuel pump on kohler 20hp v-twin.
« Reply #7 on: June 17, 2014, 04:14:55 PM »
Glad you found the problem.

I think the CV20 is the correct manual for your engine, because they list the CV670-CV680 in the engine specification section.

In the fuel section of the manual there is a troubleshooting section for a rich running condition. Possible causes are:

  • Clogged air cleaner.
  • Choke partially closed during
    operation.
  • Low idle fuel mixture is improperly
    adjusted.
  • Float level is set too high.
  • Dirt under fuel inlet needle.
  • Bowl vent or air bleeds plugged.
  • Leaky, cracked, or damaged float.

The manual also lists solutions for each problem.

I would check the easy items first before disassembling the carburetor.
John 3:16 For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life.

The Small Engine Shop

Re: oil spewing from vacuum fuel pump on kohler 20hp v-twin.
« Reply #7 on: June 17, 2014, 04:14:55 PM »