Lessons Learned Help - Onan MDKBN - Impellor Key

[rlynch03]

Anyone have experience replacing a failed key (#13) for the shaft on your water pump impellor shaft?

Looks easy enough if the slot is clean, still need to check that.

Maybe easier to just replace the body (#3).

Any help appreciated...

 

[Woody]

Why do you think the key has failed? According to the diagram yours has a 'woodruff key'. It's only job is to keep the impeller fixed in position so it rotates with the pump shaft.

My pump is different, different style key, if not install correctly the key can work endways, rub on the end coverplate and literally wear away. Because you have a woodruff style key yours can't do that. The only way it could fail is to shear off.

As far as replacement, you should be able to replace the key at the same time that you would replace the impeller.

 

[rlynch03]

Why do you think the key has failed? According to the diagram yours has a 'woodruff key'. It's only job is to keep the impeller fixed in position so it rotates with the pump shaft.

My pump is different, different style key, if not install correctly the key can work endways, rub on the end coverplate and literally wear away. Because you have a woodruff style key yours can't do that. The only way it could fail is to shear off.

As far as replacement, you should be able to replace the key at the same time that you would replace the impeller.

because there is no key there only a little nub.

 

[ttmott]

because there is no key there only a little nub.

There isn't much there. the keyway on the impeller isn't very large. You can carefully tap it out with a punch the same width as the key. Tap downward on the end of the key and it will rotate right out. I'd remove the pump from the generator before anything like that - two easy to get to bolts and it's out.

 

[Jaybeaux]

@rlynch03 I was taught that it is easier on the generator to remove the pump housing from the unit and work on it at a bench. Easy to remove. Disconnect the inlet and outlet hoses, and then its the 3 bolts/nuts/etc.

Now, both my Generators (on 2 different boats) did NOT have woodruff keys on the water pump impeller shaft. There was just a "flat spot" on the shaft which mated up to the flat spot on the impeller hub.

You say you have a MDKBN.....this is from my generator manual.

Jaybeaux

 

[rlynch03]

Thank you guys. Trying to find the key to order.

Also noticed the governor on the generator is leaking oil from the bottom. See picture. Anyone replaced it for the same reason?

One of those weekends…things breaking before a big trip (10 days to the Indian River Inlet off the Atlantic in DE, this coming weekend…



1) generator down 2) Alternator isn’t working right. I can live with this until fixed as long as I can get the generator going again to charge the batteries. 3) generator governor is leaking (a little) oil.

 

[Mjresq4]

Google Onan key 132-0374, seems readily available with bunch of sites to order from.
https://shop.cummins.com/CSSNAStore/s/product/a2w4N000003sJUiQAM/onan-key-1320374

 

[Alex F]

Thank you guys. Trying to find the key to order.

Also noticed the governor on the generator is leaking oil from the bottom. See picture. Anyone replaced it for the same reason?

One of those weekends…things breaking before a big trip (10 days to the Indian River Inlet off the Atlantic in DE, this coming weekend…



1) generator down 2) Alternator isn’t working right. I can live with this until fixed as long as I can get the generator going again to charge the batteries. 3) generator governor is leaking (a little) oil.

View attachment 148068

What you're looking for is called "governor actuator". I happened to replace mine couple years ago, but not b/c it leaked, it rather failed and the genny wouldn't stay running as the actuator was failing to maintain proper RPMs. This is about $700-$800 part. Perhaps you can get away with just new gasket, rather than a totally new actuator.

 

[rlynch03]

What you're looking for is called "governor actuator". I happened to replace mine couple years ago, but not b/c it leaked, it rather failed and the genny wouldn't stay running as the actuator was failing to maintain proper RPMs. This is about $700-$800 part. Perhaps you can get away with just new gasket, rather than a totally new actuator.

Great point I will look closer at the gasket. Is the governor a bolt on replacement? I did see it was pricey. Two or three times over the last year the generator has shut down with an Over Voltage Code. Do you recall the code you received when yours was falling?

Thank you for the intel!

 

[rlynch03]

Anyone have experience replacing a failed key (#13) for the shaft on your water pump impellore shaft?

Looks easy enough if the slot is clean, still need to check that.

Maybe easier to just replace the body (#3).

Any help appreciated...

View attachment 148053

Have any of you had to perform the “major service” (21) in the diagram? I may try that rather than the whole body. I do get a little oil past into the Impellor also.

 

[Alex F]

Great point I will look closer at the gasket. Is the governor a bolt on replacement? I did see it was pricey. Two or three times over the last year the generator has shut down with an Over Voltage Code. Do you recall the code you received when yours was falling?

Thank you for the intel!

This pic might help

A = actuator
G = governor

If I recall, actuator is held by two bolts and governor by 4 bolts.

It's been a while, so I can't say for sure. I looked though my notes and here's what I got.

Code 36 (start/stop solenoid went out. Also known as the actuator)

OVERFREQUENCY—CODE NO. 14 (Engine governor unable to maintain rated frequency)

Corrective Action:

1. If the line circuit breaker or any other circuit breaker has tripped, start the genset before resetting the breaker. (Frequency can overshoot when a circuit breaker trips under load.) If the genset continues to run, turn off or disconnect all loads, reset the breaker and bring the loads on one at a time without overloading the genset.

2. Tighten loose fuel line fittings so that air cannot be drawn in by genset lift pump suction.

3. Prime the fuel system to remove air in the fuel lines (Page 2-3).

4. Remove the governor actuator and replace it if malfunctioning (Page 4-8).

5. Disconnect connector P1 (black) from controller A1 (Page 4-1) and measure resistance between Pin 5 and A12+ and between Pin 12 and A12−. If either lead is open, check for a missing, bent or corroded pin or faulty wiring and repair as necessary.

6. Replace controller A1 (Page 4-1).



UNDERVOLTAGE—CODE NO. 13 (Controller unable to maintain rated voltage)

Corrective Action:

1. Push line circuit breaker (Page 2-2) to OFF, start the genset and measure output voltage. If output voltage is normal, reduce the number of connected appliances, especially when air conditioners and battery chargers are running. If output voltage is low, test and service the generator (Page 5-2) as necessary.

2. Replace controller A1 (Page 4-1).

 

[rlynch03]

This pic might help

It's been a while, so I can't say for sure. I looked though my notes and here's what I got.

Thank you much for all the info and detail. Very helpful.

 

[rlynch03]

Update on the Generator Sea Water Pump broken Impellor key. I ended up purchasing the entire SW Pump. It was a few hundred bucks but I am glad I did. The kit was broke off and burned (welded) in for lack of better words. So, without trying to grind the old one out I replaced the whole pump.

Back up and running again.

 

[ttmott]

Today's work - Onan Service. I guess it was due..

 

[Jaybeaux]

@ttmott Not gonna lie, I’m a bit surprised! Did you e tract the bits from the Heat Exchanger?

(I know you did!)

Jaybeaux

 

[ttmott]

@ttmott Not gonna lie, I’m a bit surprised! Did you e tract the bits from the Heat Exchanger?

(I know you did!)

Jaybeaux

Yea, this impeller had about 600 or 700 hours on it. Plus, twice in the Bahamas the generator shut down on loss of water pessure due to weeds in the water being sucked up into the strainer. I was noticing a bit more noise in the exhaust and the temperature had gone from 156 to 165 degrees the last time the boat was used. I did extract the pieces from the front end of the Hx. The anode also has about 600 hours and has eroded normally.
We run the generator from the time the boat leaves the dock until it comes back.
Oil and filter changes are a bit better every 200 hours and/or annually.