16 horse Onan

[hummod 0]

I just started a 16 horse Onan on one of my tractors for the first time today.

I took the plugs out to check for spark and blew a moderate amount of rusty

water out the front cylinder when cranking. I put the plugs back in after drying

them out. Water was only in the front cylinder. The tractor did start but only

seems to be running on one cylinder. Also there is exhaust and unburnt fuel

blowing out the carb. There is little crankcase ventilation present. The engine

only has around 250 hours on it. Does this sound like a valve seat problem or

something else? I have a different engine to put on it but I wanted to know if

the original engine is more than a boat anchor or not. Also, during all this the

oil light is flashing.

Thanks,

Larry (hummod)

[04fxdwgi 0]

Sounds like a rebuild is in order. If there was that much water in the cylinder, then

there is probably water in the oil also and now in the bearings and everything else, since it has been run.

The piston is probably all corroded and rings rusted and frozen into the ring gooves and cylinder walls all messed up from the water also.

The blowback into / thru the carb indicates the intake valve "hanging up"

(not closing) due to being siezed in the open position or rusted badly, a loose valve seat, or worse.

I would say the engine will be good as a basic door stop until rebuilt.

If it were an 18 or 20 HP unit, I would have been interested in acquiring it from you

to rebuild for a spare motor, since all these Onans (16/18/20's) are worth rebuilding unless they completely blew like a hand grenade.

[hummod 0]

Thanks for the response. I was able to get the engine apart and verify that there was

indeed an intake valve stuck open. I pulled the head and I was surprised to see the

cylinder wall in good condition. All I did was touch the valve and it popped back into

position. The cup shaped insert on the end of the valve was cracked into small pieces

and needed replaced. I put it all back together and it seems to run fine now with no

strange noises. I still have a flashing oil light but it comes an goes and may be a wire

or sensor problem. There was plenty of oil going to the top end while I was cranking

it with the lifters exposed. I will pull the head again soon to make sure everything still looks ok.

Larry (hummod)

[04fxdwgi 0]

Thanks for the response. I was able to get the engine apart and verify that there was

indeed an intake valve stuck open. I pulled the head and I was surprised to see the

cylinder wall in good condition. All I did was touch the valve and it popped back into

position. The cup shaped insert on the end of the valve was cracked into small pieces

and needed replaced. I put it all back together and it seems to run fine now with no

strange noises. I still have a flashing oil light but it comes an goes and may be a wire

or sensor problem. There was plenty of oil going to the top end while I was cranking

it with the lifters exposed. I will pull the head again soon to make sure everything still looks ok.

Larry (hummod)

Glad to hear you have it going. You must forgive my "doom and gloom" note

earlier.

I am used to building HiPo auto, marine and Harley engines and ususally find

things a tad worse than described by the owners. Usually when someone

describes "a little water", the engine is usually nearly full, as in most marine

engines I have done. I have filled some small engines through the spark

plug hole with mystery oil to free up the rings, usually, giving good results.

[wh500special 2,053]

I still have a flashing oil light but it comes an goes and may be a wire

or sensor problem.

Larry,

If the light is flashing it is trying to indicate low oil pressure. I think a loose wire would prevent the lamp from lighting since all the sender does is provide a ground path for the lamp when the pressure is low.

Before you run the engine any more you might want to get an oil pressure gauge, remove the sender for the indicator lamp, and install the tube for the gauge in that hole. Or, "tee" it in. Start and run to see if you're getting pressure. Not sure what it is supposed to be on one of these, but I'd guess 30psi would be good to see (a real mechanic like TT would know the value).

If you have pressure when cold you'll also need to warm it up and make sure it doesn't drop off when hot.

If the pressure is low or non-existant you'll need to find out why. If it seems normal, then you might need a new sender or have other gremlins in the electrics.

Steve

[hummod 0]

I fixed the oil light problem last night. The two wires on the oil pressure sensor were swapped. This caused the oil light to light when the engine was running. I moved the wire to the normally closed side of the sensor where it belongs and everything works fine now. There is an added benefit in that the hour meter works

now too. The hour meter is grounded through the oil pressure switch. I guess that was the cure for owners that left the key on by mistake and ran up the hours on the meter. I wonder what else I will find assembled wrong.

Larry (hummod)