Onan Engine P220G-I/10955G Ignition Problem

[Tinbender 5]

Toro 520 H 73502 6900471

Onan Engine P220G-I/10955G, Model 941811, SN L9534457677 in

Ignition problem history:

At times engine starts and runs fine other times engine will turn over but not start.  When I connect a spark tester the engine will start right up but will only start with the spark tester attached.  If I let the engine warm then remove spark tester the engine will start normal but misses and at times only one cylinder fires.  What's with the start up when spark tester is connected?

 

Coil primary resistance is in limits but there is no secondary resistance. I would think the engine would not start at all, puzzles me.

 

Either way I need a coil.  The parts manual shows a part number 166-0761 but I see substitute coils available. Is Ignition Coil Kit 541-0522 the correct replacement?

 

Thanks in advance.

[6bg6ga 272]

There has to be secondary resistance. Take your meter set to 100K scale and put one probe in each spark plug cable holes.    Normal resistance is going to be between 14500 -19800 ohms. My guess is the coil is faulty along with the coil wires. Take a resistance test of the spark plug wires while moving them. 

Edited April 24, 2017 by 6bg6ga

[6bg6ga 272]

Jacks small engine has PN 166-0820  for electronic ignition. You will need the mounting bracket for this coil. You get the coil and bracket under the 541-0522 part number. The old coil166-0761 that didn't need the additional bracket is no longer available unless you find someone with a NOS part. I personally do not recommend using someone's used old coil  but that's your call.

 

 

Edited April 24, 2017 by 6bg6ga

[cafoose 3,400]

I had this problem back in March and I mowed with it yesterday and it ran great so I tried starting it hot after I shut it off and it fired for one second and then did not start. I just now tested the primary coil resistance cold (I did not start it yet today) and got 3.1 ohms and the secondary gives no reading. It still starts cold and keeps running until I shut it off then will not start. I think I'm just going to replace the coil. Here is my original post:

 

 

 

[cafoose 3,400]

I just ordered this we'll see what happens when I get it.

 

http://www.ebay.com/itm/Genuine-Onan-166-0820-Electronic-Ignition-Coil-12V-For-P-Series-OEM-/221994040389?hash=item33afe03c45:g:qugAAOSwQJ5USWwu

[6bg6ga 272]

I'll tell you what is happening. If you check the coil secondary resistance when it is cold it will read. You manage to start and run the engine and the coil's secondary goes open and then it won't start. The coil is nothing but a transformer and a transformer has a primary and secondary winding.  It is impossible for the coil to function with the secondary having no reading because that would mean the secondary is open.

1 hour ago, cafoose said:

I just ordered this we'll see what happens when I get it.

 

http://www.ebay.com/itm/Genuine-Onan-166-0820-Electronic-Ignition-Coil-12V-For-P-Series-OEM-/221994040389?hash=item33afe03c45:g:qugAAOSwQJ5USWwu

 

You will need to order the mounting bracket that goes with the coil otherwise it will not mount. The original coil had a bracket built into it.

 

 

One could also parallel two single coils together as long as the primary resistance is kept within norms which would mean adding about 1.5 resistor in series with the dual coils.

Edited April 25, 2017 by 6bg6ga

[ericj 1,579]

i have heard of guy's on here buying the harley's coils, becuase they also fire both cylinder at the same time just like onan's. search for onan replacement coils on here.

 

 

 

eric j

[6bg6ga 272]

5 minutes ago, ericj said:

i have heard of guy's on here buying the harley's coils, becuase they also fire both cylinder at the same time just like onan's. search for onan replacement coils on here.

 

 

 

eric j

As long as the primary coil resistance falls between 2.90 and 3.60 your in business. The secondary resistance being a little lower will probably lower the spark output a touch. Should work fine unless the engine is really tired.

 

As i mentioned you can parallel two standard coils as long as you make sure the resistance falls between 2.9 and 3.6 ohms. Generally a standard coil runs about 4 ohms so one would simply add about 1.2 ohms to the circuit and it would work fine.

Edited April 25, 2017 by 6bg6ga

[Tinbender 5]

There is no secondary resistance reading on any range scale with either my DMM or analog meter, coil is cold. Plug wires show continuous continuity when flexed. I am puzzled how this thing even fired. I guess the coil could have totally crapped out when I last shut the engine down, beyond me. Thanks to everyone for your help/input.

 

I should have mentioned leakdown test was excellent and compression is 100 psi both cylinders.

 

Thanks 6bg6ga I ordered a 541-0522 coil and found this Instruction Sheet for installing it.

 

 

c548.pdf

[6bg6ga 272]

6 hours ago, Tinbender said:

There is no secondary resistance reading on any range scale with either my DMM or analog meter, coil is cold. Plug wires show continuous continuity when flexed. I am puzzled how this thing even fired. I guess the coil could have totally crapped out when I last shut the engine down, beyond me. Thanks to everyone for your help/input.

 

I should have mentioned leakdown test was excellent and compression is 100 psi both cylinders.

 

Thanks 6bg6ga I ordered a 541-0522 coil and found this Instruction Sheet for installing it.

 

 

c548.pdf

Tinbender,

 

Don't take anything I said wrong. Its just that a coil isn't going to function with either an open primary or an open secondary. I would bet money the engine ran and the coil ended up going open. The only other possibility is that you didn't make connection with your probes when checking it. My money is on the coil going open because I have had that happen with automotive coils in the past.

[Tinbender 5]

17 minutes ago, 6bg6ga said:

Tinbender,

 

Don't take anything I said wrong. Its just that a coil isn't going to function with either an open primary or an open secondary. I would bet money the engine ran and the coil ended up going open. The only other possibility is that you didn't make connection with your probes when checking it. My money is on the coil going open because I have had that happen with automotive coils in the past.

 

I didn't take it wrong, I appreciate your input. I was totally puzzled to find the coil had an open circuit.  I used probe extenders on both my DMM and Analog Multimeter so I know I had contact.  To satisfy my curiosity I'm going put it back together and see if it will start.  I'm thinking when I hook up the spark tester is when the coil comes to life.  I vaguely recall something about how this happens from aircraft electrical training many years ago.  My mind is not as clear as it once was.

[Tinbender 5]

Just to satisfy my mind I tested resistance on my MF135 coil and it showed 9600 ohms then I checked the Onan coil again and meter did not move (open).  I hooked the Onan coil up and to my astonishment the engine fired up and ran normal. I mowed for over two hours and right and once the engine briefly missed.  The new coil arrived and it tested at 21,600 ohms both on DDM and analog meters.  It baffles me how the engine even fired with a coil showing “open.”  Anyway, I am going to install the new coil with new plug wires.

If anyone has an answer to how this coil could work I would like to hear it. Thanks to all for your input, help and suggestions.

[6bg6ga 272]

The only thing I can think of is possibly it has a hair line wire fracture that expands enough to work intermittently. But it shouldn't be working

[Tinbender 5]

Update – After installing the new coil and plug wires I immediately noticed the engine had more power. The power loss caused by the old coil was not really noticeable because it happened over a long period of time.  The engine now performs like a new one.  I remain baffled how the old coil worked with no secondary resistance and how at times one cylinder would miss.  The other odd thing which has corrected itself is what I thought was a throttle cable issue.  Before, engine RPM would slowly creep down requiring an increase in throttle to bring it up. That is not happening with the new coil.

[cafoose 3,400]

14 hours ago, Tinbender said:

After installing the new coil and plug wires I immediately noticed the engine had more power. The power loss caused by the old coil was not really noticeable because it happened over a long period of time.  The engine now performs like a new one.  I remain baffled how the old coil worked with no secondary resistance and how at times one cylinder would miss.

Same here I noticed that after installing a new coil in mine and it runs even better since I put a new module in. I also had a surge problem occasionally and cleaned the carburetor with some improvement but now the surging is virtually gone

[Ed Stoller 19]

If the coil high voltage secondary is open, a spark can jump the gap at the fault gap as well as  fire the plugs too. The excessive total spark gap may be delaying the spark and causing the lack of power.

[6bg6ga 272]

That situation doesn't happen very often if at all.  If it did happen the timing would be far off and power would be very low that it would barely run. Its more likely the coil went open under certain temp conditions. But then again that's my .02 without being able to examine it for myself. I think we're grasping at straws here.

[Tinbender 5]

On 6/5/2017 at 6:27 AM, 6bg6ga said:

That situation doesn't happen very often if at all.  If it did happen the timing would be far off and power would be very low that it would barely run. Its more likely the coil went open under certain temp conditions. But then again that's my .02 without being able to examine it for myself. I think we're grasping at straws here.

 

Not "grasping at straws" at all just reporting facts of my experience which may help others.  I thing Ed Stoller is correct in his analysis.

Edited June 10, 2017 by Tinbender

[6bg6ga 272]

4 hours ago, Tinbender said:

 

Not "grasping at straws" at all just reporting facts of my experience which may help others.  I thing Ed Stoller is correct in his analysis.

 

 

Without being able to examine it  an internet analysis is just a flip of the coin. Sure, it could have happened as Ed speculated but then again this would be a 1 in 10,000 shot.  The conditions you had just don't happen very often. The main thing is you took the advice and changed it and all is well now.