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Save Old Iron

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Save Old Iron last won the day on April 9 2015

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About Save Old Iron

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    Listen up. I ain't just talkin' to hear my head roar

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  1. 518H 18HP Onan

    GW, In a properly functioning module , the magnetic sensor operates in either a full on or full off mode. Think of it as a light switch in your home. Either you are able to move the toggle on the light switch enough to make it flip on or off. If you don't apply enough force to "flip the switch" it just doesn't do anything and stays in it's last position. There would be no half on condition due to a weak magnet. Remember, there are 2 magnets in the trigger ring, on turns the module on and the other turns the module off. If the OFF magnet gets weak, the module will never turn off. If the ON magnet gets weak, the module will never turn on. The investigation I did for the bench test of the ignition module showed me the module seems to power up in the ON mode. So yes, the test light would come on when the ignition key is turned on. As the engine cranks. the trigger ring would turn the module on and off - thus flashing (flickering) your test light. If the tractor stopped running and you performed that same test while the tractor would not start, if the light did not flash as the engine cranked, the module is not turning on and off and therefore becomes the prime suspect of why there is no further spark. This movie is worth watching. The small black transistor on the white perf board is what is located in the "nose" of the ignition module. Pay particular attention when he describes the LATCHED version of this sensor. The magnet must be one polarity to turn on the LED and the opposite polarity to turn OFF the LED. Consider the blue LED that lights up to be the ignition coil. The magnets in his hand are the trigger ring and the black transistor looking sensor is the ignition module.
  2. 518H 18HP Onan

    I need to add to this statement. Although magnets do not lose and regain strength it is more accurate to say magnets can vary in strength when ambient temperature changes drastically (~10% lose in strength going from 32F to +200F). Less expensive ferrite magnets can vary much more than current day Neodyne composition counterparts. But once again, I do not know how hot the temps get around the trigger ring and module. If the magnets are barely adequate when cold and loose strength as the engine blocks heats up, and the ignition module looses sensitivity when it heats up, those two factors could be responsible for killing the spark. Marginal parts that fade in performance when heated - classic electronic ignition issue. You say one magnet on the trigger ring appears to be much stronger than the other. A simple test would be to lay a paper clip and the trigger ring on a piece of paper. With one magnet in the trigger ring facing the paper clip, move the trigger ring closer to the paper clip until the paper clips jumps into the ring. Measure the distance it takes to get the clip to jump on one trigger magnet versus the other. I imagine they should be about the same. If you see a big difference, the trigger ring would definitely be suspect. Jesse, are you now running with just one thickness of gasket on the ignition module? or none?
  3. 518H 18HP Onan

    Jesse, Cleat here is the best method to check the current drawn by your test lights. Mine checks out at about 120 milliamps or 0.120 amps. This amperage will certainly not strain the ignition module even when used in conjunction with the ignition coil. I have seen some test lights where the user had replaced out a defective bulb with a much higher powered car dome light that draws significantly more amperage. Note, the meter is set to read in amps with the positive lead in the designated AMPS socket. Don't forget to switch the positive lead back to the VOLTS socket and function switch back to OFF when you are finished with this test.
  4. 518H 18HP Onan

    That is correct. I'm not sure what the airflow is behind the flywheel and if the module enjoys any level of forced air cooling during engine operation. The module will be exposed to elevated temperatures from the block - probably 10's of degrees higher than the oil temperature in the block. The module is also likely to be exposed to "heat soak" issues when the tractor is shut down while the engine is hot and all air cooling is lost from the flywheel. The heat insulator would delay radiant heat transfer to the module while the engine was cooling down. Conductive heating would be present thru the module mounting bolts - no practical way to eliminate that. Best case scenario is if you mount the insulator, you issue may be cured - or at least you may start to see 30 - 40 - 50 minute runs before shutdown. This will confirm we have made a change to the predictable 20 minute shutdown cycle. IF the ignition module is compromised and still shuts off after 40 -50 minutes, you may be forced to try to put the old module back in and give it a try before buying another module. Hopefully the insulator makes a noticeable change or even cures your issue. I was rolling around the thought of "misting" the air screen area with water while the tractor was nearing its 20 minute shutdown - to see if the shutdown time was extended or disappeared. Just tossing out ideas. I have no idea what the airflow looks like behind the flywheel.
  5. 518H 18HP Onan

    The module absolutely needs a good ground. The BLACK wire from the module IS NOT A GROUND WIRE, The black wire from the ignition module performs the same function as the wire coming from the points to the coil negative post on a K series ignition - the wire BECOMES GROUNDED when the points close or the ignition module is triggered by the magnets in the trigger ring. When the second magnet in the trigger ring passes the ignition module, the black wire becomes an open circuit - just as in the points based K series ignition. The metal tab on the ignition module is the module GROUND. The heat insulator does isolate the metal tab from the engine block but the metal bolts thru the tab to the engine block establish the ground to the ignition module. As long as the module metal tab is grounded with the mounting screws, the insulator not an issue. Yes, the insulator can be too thick and displaced the ignition module nose too far away from the trigger ring. Try one thickness of the gasket material. The reason I steered you away from paper or rubber is to prevent paper from becoming wet and disintegrating when you hosed the tractor down and possibly sucked water into the module area. Paper would compress / disintegrate, loosen the module on the block and cause future issues. Same with Silicone or rubber, eventually they would compress and loosen the mounting bolts and result in an intermittent ground. Compressed asbestos-like material would be best and mimics the OEM material.
  6. 518H 18HP Onan

    Jess, bench testing the modules is probably not valuable to you as your issue has never been a no start condition. We know the modules work , but only for 20 minutes. Unless you pulled out a hair dryer and heated the modules up, bench testing is not going to help us here. I'll put together a quick movie in the next few days to show the off tractor test setup and how the module and trigger ring interact.
  7. 518H 18HP Onan

    I Ran ground to neg post from block good , one less connection to question. I have 3.5 OHMS on the Harley coil and 3.8 OHMS on the original Onan coil both are electrically similar and within published Onan primary resistance spec's. I would guess the Harley coil did not fry the ignition module. I took my test light and hooked 1 of the alligator clips to the positive side of the battery and the other to the negative post of the coil . The light stayed on ? yes, with the engine off and the ignition switch on, the off tractor testing I did indicated the ignition module powers up with current flowing thru the ignition coil. The coil being charged up when the ignition key powers up the module is probably intentional so the engine doesn't have to crank over too many times to get the first spark from the coil. No real issues so far. Question - you mentioned "one of the alligator clips" - does your test light have more than one clip ? I'm going to post another image later this morning on how to check how much current your test light draws. This may be a factor in why it causes a running engine to die. The tractor would not start with the test light hooked up so I removed it and it started right up but as soon as I try and connect the test lead to the coil the tractor would die Interesting and unexpected. When I used this procedure to test my ignition modules, it was on an engine that already had a dead coil, It never ran to begin with so obviously I never experienced an issue with the test light causing the engine to "die" when the light was connected. Interesting. Question - did the test light flash while the engine was cranking? All said and done, that was the visual indication we need to check the module. Flashing during cranking is all we really need to check the module when it dies after 20 minutes of running. I took my meter and read the OHMS on the 2 ignition module Red & Blk leads and got around 18.69 OHMS just for the heck of it . Is this something I should be getting ? I read OHMS to ground on each of the same 2 wires I get 3.5 on the Red and nothing on the Blk . Does this mean my new ing module is shot or is this the way the position of rotor might be at the time . Ohms testing on an transistorized electronic circuit is typically meaningless. Ohms measurement may be useful if the module is completely shorted and you get a 0 ohms reading, but in a transistorized module, even swapping the meter leads on the same two wires of the module can give completely different readings. As evidence of this, consider how we check a diode for proper function. Same diode device, ohmmeter reads completely opposite readings when the leads are swapped - and that's normal and anticipated to happen. Add to this a meter to meter difference in the voltage applied to the device used on the ohm meter function range and you will easily see different brands of ohmmeters will show different ohm readings. The same meter will also show different readings on the same transistorized device as you switch the meter between different resistance ranges on the meter! I have no data on how an ignition module should read with an ohmeter. I have one used spare module and another in a "one of these days years I'll get to it 520H. Should I just order another new ing module and rotor and start there again ? I'm going to go out and pull it apart and get the flywheel off and see if I can see anything in there again? If you can wait until this weekend, I know I have a spare (used) trigger ring (white color). If you want to try it with my spare ignition module, I can ship those out to you next week. I know I won't be needing them for some time. The 520H is low on my list of things to do before retirement.
  8. 518H 18HP Onan

    Hey Jesse, good to see you're back at the 518 issue. You are getting like me, everything takes two years anymore. Some random thoughts for you on the twenty minute run issue. I'm sure your head is swimming in all the help and opinions being offered on "what to replace next". You know from working with me before I do not suggest random replacement of parts on a "guess" and I treat other peoples' money as if it were my own. So, a few comments and then my suggestion for moving forward in the correct fashion on this fix. Harley Coil there are at least 3 different types of coils out on the market. For our purpose we will call them the 5 ohm coil, the 3 ohm coil and the 0.5 or "half ohm" coil. We can immediately take the "half-ohm" coil off the list of usable coils. These sub 1 ohm coils are STRICTLY for use in high energy electronically controlled automotive environments. Yes, the ignition module on the Onans are electronically controlled, but the ignition module in the Onan does not come close to the same level of design refinement seen in the automotive world. Measure the primary resistance of your Harley and Onan coils. They should be in the 3 to 5 ohm range. Stator / Regulator Do not pursue any further troubleshooting or parts replacement in the charging system. These parts only serve to keep the battery charged. A properly functioning battery should keep the 520 running for at least 1 hour even if the charge system were disconnected. I have read about your volt gauge reading being maxed out. Going forward, replacement of the voltmeter is a good idea. We need to keep an eye on the function of the regulator to assure the charge voltage doesn't skyrocket to over 16 volts. Excessive charge voltage not only will damage the battery, but can easily contribute to over stressing the ignition module. Higher voltage to the ignition module means more heat generated by the ignition module. And speaking oh heat ... Ignition Module Insulator Get one !! The last one I bought was less than $5. The addition of the insulator could very well resolve -or at least help - your problem. As a simple test, if you have access to hi temp gasket material sold at automotive stores, a homemade insulator one or two layers thick may give us some insight if heat is the root cause of your issue. Use the asbestos style compressed material for exhaust systems, not paper, rubber or Silicone. The gasket material must be rigid so it does not compress under tightening of the mounting bolts on the ignition module. 9 PIN Connector/ Jumper wires / Safety Switches. I never saw anyone mention to run a separate GROUND wire directly from the engine block back to the battery negative terminal. Bypassing the 12 volt pin in the connector by jumping the coil + to the battery + was mentioned several times but never the ground wire also located in the 9 pin connector. The ignition module needs both. Hopefully the block is grounded thru the negative battery cable, but you have to ask yourself why the Onan also has a ground wire thru the 9 pin also. Definitely worth a try. Any additional effort to bypass safety switches is just leading you in circles. The jumper from the battery to the ignition coil positive post eliminated all the wiring, ign switch. and safety switch concerns. Regulator black pigtail wire many engines that use this style of regulator mount the regulator into a plastic (un-grounded) engine shroud. The pigtail allows the metal regulator case to be grounded to the engine block by connecting this pigtail to a metal area of the engine block. It is not a bad idea to use this pigtail even on a metal shrouded engine. The ground to the regulator then does not depend on good contact between several metal shrouds to establish a good charging system ground to the regulator case. Trigger Ring Magnets Magnets tend not to lose and then regain their magnetism in 20 minutes. Think hard, when have your magnetized screwdrivers ever lost then regained their power. Weak or marginal magnets installed in black trigger rings during manufacturing - fine - that is believable. Losing and gaining magnetism - not sure anyone has seen that happen. My thoughts on how to proceed Place one jumper wire from the engine block to the battery NEGATIVE post. Grab your INCANDESCENT bulb test light. LED based testers will not work for this test. Start the tractor, run at idle. Connect the alligator clip of the test light to the POSITIVE - repeat POSITIVE battery terminal . Touch the test light to the coil NEGATIVE post and watch the lamp flash. The lamp will only flash ON briefly when the ignition coil grounds out the ignition coil. Run the engine throttle up and down and get very comfortable with the "look" of the flashing test light. This will set your visual baseline for a properly operating ignition module. While the engine is still running well, switch the alligator lead on the test light to the NEGATIVE battery lead. With the test lead wire going to the negative terminal, THE TEST LAMP WILL FLICKER OFF BRIEFLY on the ignition module grounding the coil. Choose which configuration you are more comfortable with. Hopefully you will be good with the testor wire lead connected to the POSITIVE battery lead, Some testers are quicker to respond than others due to various brands of bulbs used, so chose which method allows you to detect the flickering most clearing. Again, become very comfortable with the "look" of a properly running engine on the flickering tester. When the engine dies, hookup the tester to in the same configuration you feel most comfortable with and crank overt he engine while monitoring the coil negative post. Do not worry about the ignition coil POSITIVE terminal as any change in brightness there while cranking only shows how much your battery voltage is varying as the battery strains against the starter current - not a helpful observation. NO FLICKERING = bad ignition module FLICKERING just like when the engine was running OK = ignition module is still functioning. I would say I'm betting you will find the ignition module will be the cause of your issue., but let's check it out first and leave guessing for those with fatter wallets! I don't get much time anymore to do much online troubleshooting but I will stick with you on this one Jesse. BTW below is a slide showing the internal function of the ignition module. It is over simplified but shows the "guts" of the module are really nothing more than a magnetically controlled on and off switch that grounds the negative lead of the ignition coil. When one magnet in the trigger ring passes the nose of the module, the switch is turned on , whe the OPPOSITE pole magnet passes the nose, the internal switch is turned off and the coil fires a spark. Very simple - just like the mechanical points on the K series engines. Instead of a mechanical cam lobe, this circuit uses opposite polarity magnets to alternately turn on and then off a switch to power the ignition coil. For those of you playing at home and are more electronically inclined, the autopsy I performed years back on one of these modules reveled a Darlington pair BJT switch driver fed by a latched hall effect sensor mounted in the "nose" - about $2 worth of components just begging for someone to home-brew a replacement.
  9. Caption This 5/24/16

    then shorty after the arrival of the internet came the smartphones with cameras forcing a new view of the world courtesy of the uniformed user
  10. flywheel problem???

    spark plug wires are such good antenna that you can use them to read engine rpm
  11. flywheel problem???

    If the AC Volt functions OK with the wall socket test, try twisting the meter leads into a braid, place the meter on the ground as far from the spark plug / wire as possible and take the readings again. The meter leads are most likely acting as an antenna and the spark plug wire as a broadcast station (very similar to the interference picked up by an AM radio when held near a fluorescent light). I use Fluke 87 III meters routinely and have not noticed any interference issues when checking open stator leads - I always lay my meter on the ground and not on the engine tins or near the ignition system.. At full throttle, the spark plug fires 60 times per second and the stator design produces 18 AC cycles per spark - so the stator is about 1000 to 1100 HZ - well within the capability of a decent digital meter.
  12. flywheel problem???

    I don't know what a "beautiful" sine wave looks like but here is what the stator output (bottom trace) and points side voltage trace (upper trace) look like on an average WH charge / ignition system (thanks Mark!). No unusually high crest factors here, the quality is good enough for a tachometer to register correct RPM's on a 520. So long as the users meter is not defective, we should see a steady reading. I don't believe we ever asked what brand / model of meter you were using. If you set it to AC Volts and measure a wall outlet in your home, you should see a steady 115 to 120 VAC. Some less expensive meters are poorly shielded against radio frequencies - such as the radiation interference from a solid core spark plug wire.
  13. Caption This 5/24/16

    oh Shorpy_8b07379a, why can't you be more like Shorpy_8b07379b?
  14. 520h electrical problems

    will somebody please tell gravity to start doing its job correctly - apparently it works OK in western NY state
  15. Plastic belt cover on pto 520H

    at this point, no data has ever been presented to confirm any reduction in rear cylinder temperature by ventilating the belt cover. Evidence shows more effort has been made to perform the mod than investigate the benefit (if any) realized from the mod. My sense is this mod falls squarely under the 500 series "tribal knowledge" category and best that can be said is (like chicken soup) "it couldn't hurt".
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