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Ask Hank F. Your Own Question
Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14893
Experience:  Certified on Onan and Generac generators
19372534
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Hank - I am looking knowledgeable on marine

Customer Question

Hi Hank - I am looking for someone knowledgeable on marine generators. Specifically, a mid-90s Kohler 4CZ.
Submitted: 1 year ago.
Category: Small Engine
Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Customer: replied 1 year ago.
The generator starts fairly easily but it runs too fast. The output voltage in 150+ VAC. Then, after about 30-40 seconds (repeatable) it will shut down. After a few minutes, it will start again. It started doing this rather suddenly so I don't see why it would need a governor adjustment. I checked the excitation capacitor and it seems to charge with a DVM (in resistance mode). It does not appear to be shorted or open circuited.
Expert:  Hank F. replied 1 year ago.
Hello. Thanks for requesting me. Sorry for the delay. You are correct in that it is probably not a governor issue. Although governors can need adjustment, it is pretty uncommon, and is the last step to take (assuming no other components have been replaced). The capacitor has nothing to do with the engine running too fast - it is only for voltage regulation.But the engine running too fast will cause over voltage. Also, when working on engine speed, do not go by voltage. You need to set the speed by frequency. The over revving is most often caused by a lean condition - to little fuel getting through the carburetor.As gas gets old, it turns to varnish and clogs up the passagewaysinside the carburetor, not allowing enough gas to get to the engine.Today’s gasoline formulation goes bad in as little as 30 days.This condition is cumulative. Every time gas sits, the varnishbuilds up just a little more, like coats of paint, until eventually gas can notflow. It will not happen overnight, but the symptoms can show up allof a sudden, even while simply stopping to refill with gas.The use of fuel additives, such as Sta-Bil or Sea Foam will notstop this process from happening. They will greatly slow it down, but the gaswill still go bad. This can also happen even on a brand new engine or brand new carb.When the carb is built, it is run at the factory to tune it.After tuning, they do not always get properly cleaned, or may nothave enough/any preservative injected. Believe it or not, this is actuallyfairly common. When this happens, either the engine simply will not start, or itwill not run without the choke on (this reduces the amount of air gettingpulled into the engine, changing the fuel/air mixture), or it will run butsurges. Another issue that varnish in the carb can cause is that thevarnish may not allow the float needle to seal properly against the seat,causing the flow of gas to not shut off when the bowl is full. The result willbe gas overflowing the carb and running into the cylinder, and possibly out theair intake. If the gas gets into the cylinder, it will seep past the rings anddown into the crankcase. This will be evidenced by your oil level beingover-full and/or the oil smelling like gas.If this is the case, you will need to change the oil and filter,if it has a filter.Varnish can also cause the float needle to stick shut, and notallow any gas to flow from the carb bowl into the engine. The only 2 solutions are to either replace the carburetor or giveit a good, thorough cleaning.When removing the carb, make sure to take a good picture, or makea good drawing of where all springs and linkages are attached. This will makereassembly much easier.Most people believe that cleaning a carb involves removing thebowl and wiping it out, then spraying some carb cleaner through it.This is simply insufficient. It takes months or years for thisaccumulation to build up – it just can not be removed in minutes. To properly clean the carb, you must remove it, disassemble it(making sure to remove all non-metal parts), and soak it in a commercialsolvent for several hours. Soaking it overnight is even better.Then clean all solvent off with a spray type carb cleaner, makingsure to get lots of cleaner into every hole and passage there is. Pay specialattention to the tiny holes in the bore of the carb, under the throttle platefor the carbs that have these holes. Use lots of cleaner. And make sure to wearsafety goggles to avoid getting the over spray into your eyes. There will beover spray.Dry the carb with low pressure compressed air.When reassembling the carb, make sure to use a carb kit, when oneis available for your carb. Occasionally, even a good cleaning is not going to be sufficient,and you may end up having to replace the carb anyhow. Be prepared for this. If for some odd reason this does not help, please let meknow so I can assist you further..
Customer: replied 1 year ago.
The spark plugs look beautiful though (nice dark tan color). If I wanted to check the running rpm, where do I find a signal? The plug wires are too short to clamp on an inductive pick up tachometer. Any suggestions?
Customer: replied 1 year ago.
More history here...
The generator ran fine until I replaced a burnt wet exhaust hose and the HET sensor on that exhaust port. The previous owner had evidentially let the generator run without fresh water intake. I took the boat to the lake and it was suddenly acting up (high idle and shutting down).
Customer: replied 1 year ago.
What else can I do to troubleshoot without tearing into a carb rebuild. It seems that the kit for this is no longer available.
Expert:  Hank F. replied 1 year ago.
You check frequency through the AC output - not at the spark plugs. You could try and just adjust the governor down, but you run the risk of burning the engine up if it is running too lean.
Customer: replied 1 year ago.
OK... I figured out why the generator was shutting down. After some internet searching, I figured out that the mixing elbow where water is injected into the exhaust had a large piece of corrosion stuck in it. The rest of my problem ( high idle) was cured with an idle adjustment. I ran the generator for about 4 hours and pulled the plug. They looked very good (no sign of lean mixture).
Customer: replied 1 year ago.
Hank - I am sure you are a very competent mechanic. However, when I asked my question, I was very specific to the generator that I was having issue with. I asked " I am looking for someone knowledgeable on marine generators. Specifically, a mid-90s Kohler 4CZ." If you understood this generator, you would have recommended a number of troubleshooting steps to track down why it was shutting down after 30-40 seconds. You recommended no troubleshooting plan for this. There are four diodes on the control board that tell a good story of what is going on. You ignored this part of the problem and eluded immediately to needing a carb rebuild. I ended up resolving it myself after several hours of internet searching and hands-on measurements. The generator runs fine now. I am sure that if you were here in person troubleshooting, you would have figured out root cause in short term. Unfortunately, that is not the case. I am a pretty mechanically inclined guy. Knowing what I now know about this generator, I would not have indicted the carburetor first. I will probably request a refund. I hope you understand.