Onan 7000 Generator problems

[Sean Marconette]

I should be able to have the valve covers pulled tomorrow night. I will try and get some pictures.
Thanks

[Rich Biebel]

Sean I just read a note on one fault code page that says if the fault code shutdowns alternate between 37 and 47 it is a bad ignition coil.

You have said that you get 37 and 47 fault codes I believe.

I have seen coils fail but not very often and they do fail when they get hot. Usually only one.

Another possibility is a failed wire from the coil. It is one piece and molded in. I had one machine mice chewed thru the wire. They are carbon core wires and easily damaged right at the spark plug end....

Yes I know the coils are in the bottom of the machines lower tray.....and totally inaccessible without complete disassembly......


Sean I read some more info and here is where your problem is......

The machines controller senses engine speed from the ignition coils.....it senses generator speed from the generator at what is known as the quadrature windings. That is a small winding that makes a small AC voltage in the stator. If you lose quad output....you lose main AC output.....That never happens on your machine.....If you lose a coil the machine may shut down and does not restart probably because the coil is still not firing.....just a guess but about as good as I can come up with.

Those 2 sensing circuits are what the controller uses to compare engine speed and generator frequency. It will shut the machine down if it does not sense the proper signals from both....

I'd replace both coils....

[Sean Marconette]

The only time I have seen the code 47 was Sunday when running it in the driveway. Following checking the initial shutdown code I then tried restarting and then subsequent failures of code 37. At this point coils look to be far less expensive than heads! There are two different coils as the high tension leads are different lengths. I did inspect them both, but that means nothing with high voltage finding a path to ground.
I did order the replacement control module last night from ASAP. Supposedly it ignores all interruptions except for oil pressure and stator voltage. Could you PM the prices for the coils and a way to contact you please. I might as well have valve cover gaskets too.

Thanks Rich!

[Rich Biebel]

Yes I will Sean...

[Sean Marconette]

Well finally some progress. Side by side of the OEM Onan control module and the new ASAP module. Each cylinder head, with no signs of problems other than the valve lash was as follows:
Left (cyl#1) intake .014" and exhaust .013"
Right (cyl#2) intake .014" and exhaust .018"
I adjusted the lash to spec of .004"

The heat sink on the ASAP module is about 1/4" longer than the OEM module.

And finally for those who need to know the safe way of lifting and supporting the generator to remove the bottom structure and access the belt and coils.

I am sure the parts will be here by Tuesday and I can put this back together and in the trailer. Thanks for the help Rich

Sean

[Rich Biebel]

Heads look clean..and loose on the lash is noisy but is better than tight.

I use a set of 4 chains with a loop I made up for those machines and have two overhead rolling cranes so lifting anything is easy.

I also have a 4' square all steel heavy work table for a bench....I do all my work on that or use a forklift for diesels......Makes it a lot easier to be able to raise or lower the machine to a good working height.....

Our shop was once a steel tank fabricating business. They made any size tank and the ceiling is 20' high.....and with the cranes they could build some very large tanks....

You'll be an expert on these when your done Sean.......

[Sean Marconette]

Rick,
Although spec states .004 for valve lash, as hot as these things run is that pushing it? Should I open up the lash more?

It make all the difference in the world to have the right tools to safely work on stuff. I was half tempted to make a spreader bar for the engine hoist instead of the lifting straps that I am using. But that means planning on having to work on this more in the future! Its sitting on jack stands until I work on it, otherwise it will be lifted 4' off the floor so I can access the bottom. I can't imagine working on this thing if it was last year before I built my shop.

The overhead cranes would be great, heck the fork lift would make this even easier to get this thing in and out of the trailer a lot faster. I am sure this is a tinker toy compared to the large generators that you typically work on!

Take care
Sean

[Rich Biebel]

Sean I set the valve lash with a .004" feeler gauge. The studs tend to loosen up from the heat. I always check the exhaust side studs to make sure their tight. The lash gets tighter as you lock the locknut.....Very tedious to get them right and tight....They seem to run much better with the lash set to .004" and I just advise my steady regular customers that we need to check the valve lash every other time I do a full service on them which is at 500hrs....assuming their machines are working well....

The heat transfer from the valves to the springs/retainers etc. is usually noticeable on the exhaust side just by the color of the metal of those parts.....

The exhaust stud can loosen up and a pushrod pops out and maybe damage a rocker......all this from the heat.....

[Sean Marconette]

I can set the 16 valves on my stocker quicker than I did on the 4 valves for the generator. It did take some trial and error on where I was and then locking the adjuster down how much more they would move. So that makes sense. Do the valves tend to loosen about .010" after 500 hrs? I could easily see where a pushrod could fall out of place if this maintenance was not performed.

Sean

[Rich Biebel]

Sean they do tend to get looser rather than tighter.
BUT if the exhaust does get tighter, the lash is so small it can lead to early head failure as I have described earlier.

This is a fairly common issue on small engines with solid lifters.

It was new to me when I first started working on this equipment.

They run fine cold and after a warm up and maybe some load gets applied they start to run badly.....shut it off....cools down.....cycle starts all over again....

Onan flathead engines did this pretty regularly......They had a very wide exhaust lash spec at .013"

Exhaust valve needs to touch the seat every cycle to shed some heat of combustion from the valve....No touch.....valve overheats and it magnify's the problem.....

Small engines were a whole new world to me going back 15-20 years ago...

Chasing some of these problems has always been a challenge to say the least....