12 HP Kohler compression question

[608KEB 795]

I bought a 1999 WH 312-8 last winter for my father. When starting it if it kills.  When he tries to restart it. It won't turn over unless he removes the spark plug to relieve the built up compression. The engine has the OHV. How can we fix this?

[Ed Kennell 38,579]

Have you checked the valve clearances?  They could be too loose not allowing the valves to open and release the compression.

Could be the ACR  (automatic compression release) has failed.  If the cylinder is flooded with fuel, could be a carb needle valve failure or hole in the float in  the carb bowl.

[gwest_ca-(File Mod) 11,088]

Click on the picture

Garry

[cleat 6,297]

My 312 has a Kohler Magnum. Is the manual similar ?

 

[WHX?? 49,100]

Battery, starter & cables up to snuff?? ...just a thought.

[608KEB 795]

On 6/28/2018 at 6:07 AM, Ed Kennell said:

Have you checked the valve clearances?  They could be too loose not allowing the valves to open and release the compression.

Could be the ACR  (automatic compression release) has failed.  If the cylinder is flooded with fuel, could be a carb needle valve failure or hole in the float in  the carb bowl.

I was wondering if it had a ACR. Where is that located. That would be the first thing I should check.

[608KEB 795]

It won't turn over because of pressure that has built up in the cylinder. If I take the plug out. It'll turn over no problem. If I put plug back in it starts right up.

Edited July 1, 2018 by 608KEB

[608KEB 795]

On 6/28/2018 at 7:54 AM, WHX20 said:

Battery, starter & cables up to snuff?? ...just a thought.

Yes

[953 nut 55,700]

            So, when you begin to back out the spark plug do you hear the pressure releasing? It couldn't hurt to clean and tighten all electrical connections including grounds. Also, have the battery load tested.

[608KEB 795]

On 7/1/2018 at 6:42 PM, 953 nut said:

            So, when you begin to back out the spark plug do you hear the pressure releasing? It couldn't hurt to clean and tighten all electrical connections including grounds. Also, have the battery load tested.

I'll check it and report my findings

[608KEB 795]

Could someone post a picture  as to where the ACR is located on this motor? I did not find it in the manual.

Edited July 17, 2018 by 608KEB

[Anglo Traction 761]

Hi, I confess to know virtually zero about this engine, but to offer some clarity. 

I believe your engine is as per the Service Manual link provided by Garry earlier, i.e CH12.5.   ACR System is described in Section 10 page 1 (page 89 of the Manual).

As your engine operates with Hydraulic Valve Lift using full Oil pressure, I would suspect the possible cause lies with intermittent sticking Valve Lifters (or Oil pressure) on start up, or the ACR lifting pin is faulty. 

For an engine to build up such pressure in the cylinder and to have to undo the Spark Plug to relieve it, neither valve is lifting when it should, but at least you must have good seals on piston rings and  valve seats to store the pressure.

I'm sure there are members here with experience of this model and will point you in the right direction to resolve it.

Regards        

Edited July 17, 2018 by Anglo Traction

[608KEB 795]

15 hours ago, Anglo Traction said:

Hi, I confess to know virtually zero about this engine, but to offer some clarity. 

I believe your engine is as per the Service Manual link provided by Garry earlier, i.e CH12.5.   ACR System is described in Section 10 page 1 (page 89 of the Manual).

As your engine operates with Hydraulic Valve Lift using full Oil pressure, I would suspect the possible cause lies with intermittent sticking Valve Lifters (or Oil pressure) on start up, or the ACR lifting pin is faulty. 

For an engine to build up such pressure in the cylinder and to have to undo the Spark Plug to relieve it, neither valve is lifting when it should, but at least you must have good seals on piston rings and  valve seats to store the pressure.

I'm sure there are members here with experience of this model and will point you in the right direction to resolve it.

Regards        

Thank you, I read through it. Am I going to have to take the engine apart to fix this? The manual says the ACR is on the cam shaft?