TC10284 109 #1 Posted October 5, 2018 I picked up a 1991 41-20OE02 520-H the other weekend. The guy said it wouldn't fire. He had also replaced the fuse block with one that wasn't like the original (4-way), including took off the fuel pump and tried to install an electric fuel pump. So I took off the electric fuel pump, replaced with a new fuel pump just like the original (the pulse kind), and also bought a new 4 way fuse block. Today I connected all the wires to the new fuse block. He gave me the original fuse block that he clipped off (I cringed when I saw this). Put the wires back in their original location: White and purple on fuse location 1 Red and red on fuse location 2 Pink and pink on fuse location 3 Connected a battery, engine turns over, but no fire. It's definitely getting fuel. I can smell it on the plugs and I can see it pumping through the filter. I tried pulling the spark plugs, one at a time, and I see no spark from either one. The only time I see spark is when I flip the key from Run to Off. I don't think it's wiring. I feel like it might be the ignition coil or capacitor. But I do not know how to test this. The other issue I have is that the dash lights come on as soon as I connect the battery. What I think is happening here is that the replacement fuse block has one side where all the PICO 1598D connectors connect to is getting energized on the dash lights. So I'm thinking I might be able to clip it between fuse location 2 and 3 to break that connection. Wouldn't that work? I pulled the fuse and the dash lights went out when I did so. This is the item: https://images-na.ssl-images-amazon.com/images/I/61MLvIzHm9L._SL1500_.jpg Share this post Link to post Share on other sites
520hC-120 136 #2 Posted October 5, 2018 How to check if you have power in and out of a coil. Get your test light or voltmeter. Put key in run position. Get a good ground on test light or voltmeter. Put positive or light on negative post for coil should have constant light. Crank engine over and light or volt reading should pulsate. guys correct me if I’m wrong I haven’t needed to do this in a while Share this post Link to post Share on other sites
WVHillbilly520H 10,369 #3 Posted October 5, 2018 I like the inline spark testers... https://www.harborfreight.com/in-line-spark-checker-63590.html...here's some pages from the Onan manual 1 Share this post Link to post Share on other sites
TC10284 109 #4 Posted October 5, 2018 11 hours ago, WVHillbilly520H said: I like the inline spark testers... https://www.harborfreight.com/in-line-spark-checker-63590.html...here's some pages from the Onan manual Thanks! I'll give this a try and let you guys know. 1 Share this post Link to post Share on other sites
gwest_ca-(File Mod) 10,441 #5 Posted October 5, 2018 A good set of wiring diagrams. Click on the picture Garry Share this post Link to post Share on other sites
lynnmor 6,698 #6 Posted October 5, 2018 Because there is a spark when operating the ignition switch, my guess is the ignition module is defective. Share this post Link to post Share on other sites
TC10284 109 #7 Posted October 5, 2018 3 minutes ago, lynnmor said: Because there is a spark when operating the ignition switch, my guess is the ignition module is defective. Sorry to sound dumb, but that's the same as the ignition coil, isn't it? Share this post Link to post Share on other sites
lynnmor 6,698 #8 Posted October 5, 2018 Just now, TC10284 said: Sorry to sound dumb, but that's the same as the ignition coil, isn't it? No, look at the pages posted above. 1 Share this post Link to post Share on other sites
TC10284 109 #9 Posted October 5, 2018 3 minutes ago, lynnmor said: No, look at the pages posted above. I see what you're saying now. Share this post Link to post Share on other sites
TC10284 109 #10 Posted October 6, 2018 On 10/4/2018 at 9:18 PM, WVHillbilly520H said: I like the inline spark testers... https://www.harborfreight.com/in-line-spark-checker-63590.html...here's some pages from the Onan manual I tested the coil using the method in your pictures. I got 3.5 ohm on the primary wires. On the secondary set, I get infinity. So I'm guessing this coil is bad. To confirm, I tried another voltmeter. And went even further by connecting the plug wires to the coil to make sure I was making contact with the coil and that my voltmeter terminals weren't too short. Guess I'll be ordering another coil. 1 Share this post Link to post Share on other sites
cleat 4,895 #11 Posted October 6, 2018 I just ordered 2 coils straight from China, They come with the mounting brackets and I have one installed and it works great. I paid $39.85 with free shipping. This was an ebay purchase (Ignition Coil Fit Onan 541-0522 166-0820 HE166-0761 HE541-0522 P Models New) is the listing description . Cleat 1 Share this post Link to post Share on other sites
TC10284 109 #12 Posted October 7, 2018 4 hours ago, cleat said: I just ordered 2 coils straight from China, They come with the mounting brackets and I have one installed and it works great. I paid $39.85 with free shipping. This was an ebay purchase (Ignition Coil Fit Onan 541-0522 166-0820 HE166-0761 HE541-0522 P Models New) is the listing description . Cleat Thanks! I ordered one. Share this post Link to post Share on other sites
BMW Phil 0 #13 Posted October 10, 2018 Have you checked the oil pressure safety switch? I picked up a 520-H last summer, non-runner, for free. Got it back to the shop and found no spark. Ran a jumper from bat+ to coil+ and it started right up! I changed the oil, with some Seafoam added, ran it awhile, and put away my jumper wires. Been using it ever since. Share this post Link to post Share on other sites
TC10284 109 #14 Posted October 11, 2018 On 10/10/2018 at 5:07 AM, BMW Phil said: Have you checked the oil pressure safety switch? I picked up a 520-H last summer, non-runner, for free. Got it back to the shop and found no spark. Ran a jumper from bat+ to coil+ and it started right up! I changed the oil, with some Seafoam added, ran it awhile, and put away my jumper wires. Been using it ever since. No I haven't. Only disconnecting the oil safety switch. I got the new coil in today and will try it once it stops raining from Hurricane Michael. Share this post Link to post Share on other sites
cleat 4,895 #15 Posted October 11, 2018 Never seen one with the low oil pressure switch as part of the ignition circuit. Some of them stop the hour meter with no oil pressure. I have one of those coils in operation now and it works great. Cleat Share this post Link to post Share on other sites
TC10284 109 #16 Posted October 12, 2018 On 10/6/2018 at 5:30 PM, cleat said: I just ordered 2 coils straight from China, They come with the mounting brackets and I have one installed and it works great. I paid $39.85 with free shipping. This was an ebay purchase (Ignition Coil Fit Onan 541-0522 166-0820 HE166-0761 HE541-0522 P Models New) is the listing description . Cleat Might be a dumb question, but I looked at this some tonight and I'm not exactly sure how to get the replacement to fit into mine. The original has a squared side on it, while the replacement is a completely cylinder. Do I remove the third screw that sits a little further out on the metal plate? Share this post Link to post Share on other sites
cleat 4,895 #17 Posted October 12, 2018 Not the best picture but all I have on the computer right now. New coil gets clamped into the supplied bracket then the bracket and coil get bolted down using the shorter screws provided with the kit. You just rotate it around until 2 holes line up, I think one of them will be under the long tab sticking out of the bracket. Coil will sit higher than it used to but it will still clear everything. I can get better pics tomorrow if required. Cleat Share this post Link to post Share on other sites
TC10284 109 #18 Posted October 13, 2018 (edited) Put on the new coil and condenser. Still the same problem. Spark plugs will fire the first time I turn key to Start and not fire again until I switch key to Stop. I cannot locate the oil safety switch. Where is it located? I broke the positive terminal on the coil tightening it down a third time. Didn't even put a lot of pressure on it. Chinese crap. Guess I'll be buying a new one. Edited October 13, 2018 by TC10284 Share this post Link to post Share on other sites
cleat 4,895 #19 Posted October 13, 2018 Must me the module located behind the flywheel. I have only had one of these fail but it does happen. Did you overtighten the terminal screw ? Mine has worked great. Cleat Share this post Link to post Share on other sites
TC10284 109 #20 Posted October 13, 2018 1 hour ago, cleat said: Must me the module located behind the flywheel. I have only had one of these fail but it does happen. Did you overtighten the terminal screw ? Mine has worked great. Cleat No. It wasn't even snug when I tightened it. Is there a specific part number for the ignition module? Share this post Link to post Share on other sites
cleat 4,895 #21 Posted October 14, 2018 Part number is 166-0785 or 71-6380. Expensive part, you should verify proper operation first. Try this test. Troubleshooting the electronic ignition module for P Series.pdf Cleat Share this post Link to post Share on other sites
TC10284 109 #22 Posted October 14, 2018 29 minutes ago, cleat said: Part number is 166-0785 or 71-6380. Expensive part, you should verify proper operation first. Try this test. Troubleshooting the electronic ignition module for P Series.pdf Cleat Hey awesome. That's a handy test. Couldn't I use a voltmeter instead of a test light to see if the voltage drops when engine is turned over? Share this post Link to post Share on other sites
cleat 4,895 #23 Posted October 14, 2018 You could use a volt meter, just roll engine over by hand and watch for voltage to go from 12 to 0 to 12 etc as you turn it. Starter will likely roll it too quick to see, especially if you use a digital meter. Share this post Link to post Share on other sites
TC10284 109 #24 Posted October 14, 2018 (edited) 11 hours ago, cleat said: You could use a volt meter, just roll engine over by hand and watch for voltage to go from 12 to 0 to 12 etc as you turn it. Starter will likely roll it too quick to see, especially if you use a digital meter. Found a 12v led light. Test 1. Light did not come on when turning over the engine. Only when turning key from run to stop. A quick flash. Test 2. Light stayed on when turning over the engine. Looks like I need a new ignition module. I also found evidence of mice chewing a green wire on top of the engine for the headlights. It is partially naked but not shorted. So I would also like to check to see if the ignition module wires are shorted out or something from mice chewing. But I'll have to take the time to take off the shroud since I'm going to be possibly replacing the ignition module anyway. Edited October 14, 2018 by TC10284 Share this post Link to post Share on other sites
TC10284 109 #25 Posted October 15, 2018 Update: Took off shroud. Connected positive terminal on voltmeter to negative post on coil. Connected negative terminal on voltmeter to a ground on the engine. Turned key to Run. Showed 0.9v on voltmeter. Turned flywheel by hand. Voltmeter showed a solid 0.9v and didn't change a bit. Could not see anywhere the mice had chewed into the wires. So I ordered this kit: https://onanparts.com/index.php?main_page=product_info&products_id=737&zenid=e409078fc63d13544c98b9e8d15cefb1 Share this post Link to post Share on other sites