520h.. Cranks but no start..

[Mt Zion 520H 43]

So I was mowing for about 45 minutes when I heard a pop and engine shut off. I checked fuses thinking maybe one went and they are fine. Tried to restart and it cranks and cranks but won't start. What might be the issue?

Thanks in advance.

[lynnmor 6,847]

One problem area is the ignition module, it can fail when hot.  One test is to stick a spark plug on a wire and ground the threaded part, then crank while watching for spark.  Let the engine cool down and try again.  Here is some information about that.

[Gasaholic 183]

Look at the coil also, see if it looks like it sits down "inside" the blower housing under air filter housing, or if it sits on a newer bracket that sits the coil a bit higher. Onan had a common issue with those coils - a high failure rate - and issued a new service kit with new coil and a bracket that brings coil up higher out away from engine block to reduce heat failures. - last I knew of kit was around $250 (coil plus bracket kit plus instruction sheet & hardware)  That's one of the first things I looked at when I got an Onan Performer (Or the Toro branded one) at my shop. about 80% of the time a crank with no spark was a result of failed coil. (as long as I was seeing 12V at coil from battery, that is.)  only once ever did I see the trigger ring experience a failure (but that was when the alternator magnets got something in them and grenaded) and the rest of the time it was coil wires, shorted spark plug,  or no power getting to coil (tractor wiring problem) 

[lynnmor 6,847]

3 hours ago, Gasaholic said:

Look at the coil also, see if it looks like it sits down "inside" the blower housing under air filter housing, or if it sits on a newer bracket that sits the coil a bit higher. Onan had a common issue with those coils - a high failure rate - and issued a new service kit with new coil and a bracket that brings coil up higher out away from engine block to reduce heat failures. - last I knew of kit was around $250 (coil plus bracket kit plus instruction sheet & hardware)  That's one of the first things I looked at when I got an Onan Performer (Or the Toro branded one) at my shop. about 80% of the time a crank with no spark was a result of failed coil. (as long as I was seeing 12V at coil from battery, that is.)  only once ever did I see the trigger ring experience a failure (but that was when the alternator magnets got something in them and grenaded) and the rest of the time it was coil wires, shorted spark plug,  or no power getting to coil (tractor wiring problem) 

Cheap aftermarket coils with hardware are available, I have success using them but I am sure quality varies.  If @Mt Zion 520H follows the information linked in my first post he should be able to find the actual problem without wasting money on unneeded parts.

[Mt Zion 520H 43]

17 hours ago, lynnmor said:

Cheap aftermarket coils with hardware are available, I have success using them but I am sure quality varies.  If @Mt Zion 520H follows the information linked in my first post he should be able to find the actual problem without wasting money on unneeded parts.

Thanks brothers.

I pulled fuses, harness plug and sprayed with contact cleaner. Pulled spark plugs, cleaned up a little with sandpaper (weren't that bad), sprayed them off with contact cleaner and inside the boots. Put the rear back in and used front plug for spark check but got nothing against different metal locations.

Guess I gotta go deeper and pull the air cover off.. Etc etc.. I don't have a tool to pull fly wheel off at the moment though. Any other way to check before going that far?

[Gasaholic 183]

NO need to pull front cover or flywheel if it is the coil, which I would bet it most likely is. As I mentioned, I do not believe I have pulled flywheel for an ignition problem on any but perhaps 2 or 3 Onan performers in the last 30-plus years if wiring, coil wires & plugs are eliminated (Power to coil when cranking? both plugs grounded? Some Onans I don't remember which, needed both cylinders grounded via plug wires hooked to plugs, with plugs grounded, to produce spark on either side.)  Plug wires from time to time can fail, but I'll lay odds you need a new coil, as I mentioned. A practiced, experienced tech can have the job done in 10 minutes or less. - pop air cleaner cover & base off the carb, unhook coil (note where wires go), remove old bracket (if you are using the update kit)  pop in new bracket & coil, wire 'er up and away you go. Shrouds don't really need to be removed (Though I usually will at least unbolt them and pop front shroud off so I can get air hose nozzle in and blow out cooling fins and check the oil filter base for leakage which was another common problem with the Performers) 

 

I recall now a quick test I would do with those was to put a test LIGHT on the coil/module wires to check for 12v to coil, and when cranking the test light would flicker/flash if the coil was firing , but would not do that when coil was bad (Though coil can still have failure)  only reason you would have to remove flywheel would be to replace the reluctor ring & sensor (that sends timing trigger to the coil/module) and as mentioned, I don't think I have ever had to replace those except a couple times or so.. the way they are designed, there is very little to go wrong with them unless you physically damage something. It's either plugs, plug wires, power supply to coil, or the coil itself, and once you eliminate the easy stuff, only thing left is the coil/module which sits under the air cleaner base. 

Edited August 27, 2023 by Gasaholic

[Mt Zion 520H 43]

1 hour ago, Gasaholic said:

NO need to pull front cover or flywheel if it is the coil, which I would bet it most likely is. As I mentioned, I do not believe I have pulled flywheel for an ignition problem on any but perhaps 2 or 3 Onan performers in the last 30-plus years if wiring, coil wires & plugs are eliminated (Power to coil when cranking? both plugs grounded? Some Onans I don't remember which, needed both cylinders grounded via plug wires hooked to plugs, with plugs grounded, to produce spark on either side.)  Plug wires from time to time can fail, but I'll lay odds you need a new coil, as I mentioned. A practiced, experienced tech can have the job done in 10 minutes or less. - pop air cleaner cover & base off the carb, unhook coil (note where wires go), remove old bracket (if you are using the update kit)  pop in new bracket & coil, wire 'er up and away you go. Shrouds don't really need to be removed (Though I usually will at least unbolt them and pop front shroud off so I can get air hose nozzle in and blow out cooling fins and check the oil filter base for leakage which was another common problem with the Performers) 

 

I recall now a quick test I would do with those was to put a test LIGHT on the coil/module wires to check for 12v to coil, and when cranking the test light would flicker/flash if the coil was firing , but would not do that when coil was bad (Though coil can still have failure)  only reason you would have to remove flywheel would be to replace the reluctor ring & sensor (that sends timing trigger to the coil/module) and as mentioned, I don't think I have ever had to replace those except a couple times or so.. the way they are designed, there is very little to go wrong with them unless you physically damage something. It's either plugs, plug wires, power supply to coil, or the coil itself, and once you eliminate the easy stuff, only thing left is the coil/module which sits under the air cleaner base. 

Thanks for that info brother.

I was just out doing some tests and here's what I found..

With dvom Pos lead to Neg post and Neg lead to beg on battery; Voltage jumps from 12 to 5 volts halfway and back when manually turning flywheel clockwise.. Not a steady climb... Instructions don't say it it should be or not but does say should be 12v to 1v. Maybe I'm doing it wrong but can't get it to go from 1 to 12v.. And don't see timing markings on the shroud housing.

 Ohms on the posts are off too so seems that needs replaced and hopefully I'll be back in business.

Edited August 27, 2023 by Mt Zion 520H

[Gasaholic 183]

Yup coil failure. The reason a test light would flicker (and the voltage switches from 1 to 12 v) is from the ignition module transistor switching between open circuit and ground (Which is what breaker points do) and the transistor is being triggered by the reluctor ring (There is a press-fit ceramic-ish ring that presses onto the crankshaft and then the ring sensor mounted to block that uses magnetism to turn on and off the circuit, which is where the timing setting comes in. I recall first time we had to replace that, boss had to order a VERY expensive special tool kit from WheelHorse/Toro/Onan to remove and replace that stuff. Should have heard him cussing when he looked up the price!) 

 

The fact that voltage WON'T switch to 1V (which is when the transistor switches to ground / points closed) would indicate that there is a short internally in the electronics (albeit a high resistance) that allows voltage to flow through - If there's voltage flowing in the primary windings of the coil all the time, there's no collapse of the electromagnetic field that induces the voltage in the secondary winding (which translates into a 20,000 volt spark to jump your spark plug gap under compression) So, if there's never a collapse of that voltage from 12 to 1 (or less) volts which has to happen quite quickly there's never enough voltage induced into the secondary to produce spark.  What I think happens usually internally to the coil is the insulating media (Sort of an epoxy) surrounding the circuits breaks down and cracks through due to high heat (Since the original configuration the coil sat pretty close to the engine block in an area that does not see a whole lot of cooling air flow) and eventually develops enough contamination (dust/carbon/silicates) to short the circuit to ground, allowing continuous voltage flow through primary winding.  The new Onan coil update kit from Onan when you ordered a new coil included a new bracket and some hardware bits and instruction sheet to move the coil mounting a little bit higher away from the block to reduce heat related failures.  I'd suspect aftermarket coils may not include those pieces, so if I was installing an aftermarket coil knowing what I know from prior OE kits, I'd probably at least try to mount it as far away from engine heat/block as possible.  

 

Most of the coil failures I HAVE seen like that are almost always on machines that were NOT well maintained, but not always, so I'd say preventing future failures, maintenance of the cooling system would be pretty important - at least annually popping tins off and blowing out accumulated crud & debris. (Or with every oil change) 

[lynnmor 6,847]

Installation instructions for the new type of coil, I think that aftermarket coils are mounted the same way but rarely have these instructions.

 

You likely don't need timing instructions but they are contained in the page you copied and pasted in your post.  The timing mark can be seen down the hole where the pipe for the air cleaner enters and you guess if it aligns with the screw shown.

 

I have had one coil fail and two ignition modules fail, testing the modules are hit or miss since they fail under heat and test fine a couple of minutes later. 

 

A simple flywheel puller can be made from a steel plate drilled to match the four holes in the flywheel face.  In the center, drill and tap a hole for a bolt.  Fasten the plate using four screws, then turn the center bolt in till it pops the flywheel.  Instructions are on page 10-6 of your Onan Service Manual.

[Mt Zion 520H 43]

4 hours ago, Gasaholic said:

 

 

2 hours ago, lynnmor said:

 

Thanks again Fam.

Where should I look for another coil? Ebay? Not finding much on amazon.. Like 1 with 4 ratings and only 1 review.. Lol.

 

[Mt Zion 520H 43]

Just to share..

[Mt Zion 520H 43]

Ugh.. Can't upload other pic. Between that is all about 5.24v. Lol

[lynnmor 6,847]

4 minutes ago, Mt Zion 520H said:

 

Thanks again Fam.

Where should I look for another coil? Ebay? Not finding much on amazon.. Like 1 with 4 ratings and only 1 review.. Lol.

 

There is a ton of them on Amazon.

[Mt Zion 520H 43]

Guess this is the one.. Listing is a little confusing to me with the info but does say for Onan P220G. Wish me luck..

Partman Ignition Coil Fit for Onan P218G P220G P224G Model 541-0522 166-0820 HE166-0761 HE541-0522 166-0772 https://a.co/d/inpZe5H

[Mt Zion 520H 43]

Yup. That was it. Thanks again brothers.