Onan won't run at all

[waffle 26]

Well.... bought a 416H with the twin P216 engine that original owner said can't start anymore with the plan on going all through the whole tractor and bringing it back to life. After spending time and too much money on new tires, all fluids and filters, etc, can't get it to run at all. Had many Kohler engines with zero trouble getting them going. very little experience with these Onan engines and ready to give up and shove aside or sell like it is.... Maybe somebody can give me a clue on something I have missed....

 

 What I have done to engine so far....... Had zero spark so bought the ignition module kit that a guy sells on Ebay and now have great spark. Fuel to cylinders gets there fine. Compression check shows 110psi to both cylinders. Spark plugs good. All I get is backfire thru the carb and engine just spits and sputters badly but won't run even a few seconds. Acts like timing is way off but have no experience with how to time these oman's or why it would be off. 

 

  What else can i do before I throw in the towel for now?

[rmaynard 15,509]

Where did you check for spark? Do you actually have spark at the tip of the plugs? Have you replaced the plugs? I'm just grasping at straws here.

[Ed Kennell 38,203]

I assume you pull the plugs and find a wet plug to know it is getting fuel.   Could a too rich fuel mixture be drowning the plugs.  Liquid gasoline will not burn, It has to be a vapor.

[ri702bill 8,327]

And let us not forget to check the condition of the infamous 9 pin connector for signs of meltdown......

[waffle 26]

  Yes, swapped plugs with another Onan that I have that runs fine, spark is great at the plugs and won't try to start with a dry or wet plug.... I even swapped plug wires from front and back cylinders on the coil just because in case previous owner tried something and got them swapped. Speaking of that, have seen plug wires hooked up differently on youtube videos and wonder what not all the same........swapping plug wires did not seem to make any difference at all that I could tell...... Don't know anything about a 9 pin connector, but I'll go look now.

[Ed Kennell 38,203]

 

42 minutes ago, waffle said:

..swapping plug wires did not seem to make any difference

And it shouldn't, on the Onan twins, both cylinders fire at the same time every revolution of the crankshaft. One cylinder fires on the power stroke while the other cylinder fires on the exhaust stroke

[Bill D 1,922]

Was the flywheel properly torqued after the module was replaced?  If not is the flywheel key sheared?  That will throw the timing off as the trigger ring will not be in the correct spot.  That happened to another member here.  Is the ignition module correct for that engine.  I've seen different part numbers for that module.  I don't know if that affects timing.

 

How many hours?  Did someone decarb the cylinders and set the valve lash?  If so did they do it correctly?  The valves could be opened slightly if the lash isn't set correctly, even if you're showing good compression.

[c-series don 8,719]

My first thought was flywheel key sheared? But I’m guessing as well. 

[waffle 26]

Interesting on the firing of the cylinders. So does that mean no matter which way you put the wires in, all will work fine?  Well the part number on the trigger and the module are #166-0785 and #166-0767. The key is very good on the shaft and the engine only has 638 hours on it. Maybe I assumed wrong that the valves are adjusted at least good enough to run when I got the 110psi reading? I have not actually checked yet and if you guys think maybe its a problem, then I will but not til tomorrow when I have time.

[rmaynard 15,509]

This may be a wacky suggestion, but just out of curiosity, take off the air cleaner and spray some starter fluid, carb cleaner or brake cleaner directly into the throat of the carb and see what happens when you try to start it.

Before I replaced the carburetor on my 416-H, I could crank it for what seemed like minutes and it would not fire. But a shot or two of brake cleaner fired her right up.

If she runs on the "starter" fluid, you have a carb or pump problem. 

[Ed Kennell 38,203]

3 hours ago, waffle said:

So does that mean no matter which way you put the wires in, all will work fine?

Yep.        Sounds like the only part left is the carb.   Have you done any cleaning/adjusting to the carb?     Does it act any different with the choke open vs closed during start up?

Any chance the muffler is totally blocked?

[waffle 26]

Well, checked the valves and they were right in spec, hardly had to adjust..... Cleaned the carb, put back on as all looked fine..... Tried to start using starter fluid. Same thing, just spit and backfired a bit again acting like somehow timing off but don't know what to do about that..... Guess my patience has run out, very frustrated. Bought hoping to bring back to life, put one of my snowblowers on it and sell it as a nice turnkey machine for somebody. Spent to much money and time on it at this point and I'm in need to work on other projects so going to shove aside I guess... thanks for all your suggestions as it is much appreciated.... Anybody want to buy a mystery project!!!!! 

[rmaynard 15,509]

I would not give up on this engine. First, you said that the previous owner could not get it to start. Are you able to contact the PO and ask a few questions like; did he do any work to it? How long ago was it last running? 

There has to be a clue somewhere as to what happened to it. If he or someone else took it apart, why? Did the engine just stop running suddenly or was it a slow death?  Did it make any weird noises prior to stopping? Any engine that just suddenly stops without making any internal noise should be able to be repaired. If you have the facilities and the time, I would do a complete tear down and rebuild. A P-216 is just too nice of an engine to give up on.

[waffle 26]

Well an older lady bought this new so one owner. I bought from her son who told me she went out and bought another lawnmower when the deck of this was seizing up from a bad bearing which I have fixed for another WH I have. He told me it has been sitting for a few years outside and when he tried to start it would not. He was a mechanical inclined guy based on what else I saw around there place he works on so don't trust he did not try to work on this and quit. Just saw no evidence of it being messed with but who knows. I have spent enough and no more time to tear apart til maybe winter here in Western NY when things are quiet. Hoping I will find a running Onan in a good parts tractor I can just transplant into this or just sell along with a few other WH snowblowers I need to get out of my way. We shall see. Anybody want a mystery problem project to buy!....

Edited August 23 by waffle

[waffle 26]

great news update..... well decided to dig in deeper to give it one more shot before setting aside... And the one thing I told myself to be careful of and don't screw it up, I screwed up. When I swapped al the parts out for the new ignition module kit I bought, I put the magnet in backwards!!! So it was all my boneheaded fault for not remembering to check the magnet went in with the "Flywheel side out" actually out! Sorry guys! Learned a lot about these Onan engines during this exercise for sure. Starts and runs like a champ now.

[lynnmor 7,307]

Here is a photo of the part:

[oliver2-44 9,758]

2 hours ago, waffle said:

great news…… Starts and runs like a champ now.

That all that matters.