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9020 Onan


TerryZ

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I bought a fixer upper 9020 last year with the Onan 20Hp. It didn't run so good until I replaced the points and correctly installed the condensor (it was loose and therefore not grounded well). I also replaced the mechanical fuel pump with an electric unit. Rebuilt the carb, cleaned the plugs, repelaced the plug wires - the usual stuff. After replacing the left rear wheel bearings, new rear tires, new front axle pivot bushings, refurbishing the mower deck, and fixing a host of other small problems I got her running very well for about 20 hours... Now the engine misfires intermittantly and has almost no power. Everything is tight, points looks good, checked the plugs, gas is good, lines not plugged, great compression, no smoke, no unusual noise. Can't seem to find anything wrong - Any ideas?
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Recheck the points. I've had the most problems w/ this on the CCK engines. The points box will work loose if the mounting screws are worn and the screw's that mount the points and cond. may work loose not grounding things as you found earlier. The only other thing I can think of is a clogged air filter. But your most likely going to find ign. problems. You might also check the output of the coil.
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Terry, what are you using for spark plugs? The CCKA and CCKB engines are prone to fouling plugs, even with low hours on them. NGK plugs seem to be the plugs of choice for these engines. The NGK # is: B-6L. They worked good for me. Let us know how you make out?
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You want to use a timing light! As Jim & Dave mention, the ignition is one of the Onan weak points! NGK, Autolite seem to work well. Make sure the points screws aren't stripped. Is the points box free of oil? Keep us posted JP
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Thanks guys! I will replace the plugs, double check the points, and check timing this weekend. Has anyone tried to replace the points with one of those electronic modules? It uses the points for timing but the points are spared the power surges of driving the coil - the module drives the coil. I got one off of ebay that is made for small engines and am considering to try it on the Onan.
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Hey Terry, Give this a whirl! See them on Ebay a lot.... http://cgi.ebay.com/ebaymotors/Pertronix-electronic-ignition-ONAN_W0QQcmdZViewItemQQcategoryZ33691QQitemZ7998062613QQrdZ1 Haven't had time to try it, Always have been curious though..... JP
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THis article may be of interest. http://www.gmcws.org/Tech/onan_electronic_ignition/onan_electronic_ignition.html The first box shown looks like the one on my 9020. When I replaced it the part number was 160-0257. My dealer did say that Onan makes changes to the numbers quite often. I wonder if Onan can advise if this Electronic Ignition Kit P/N 160-11376 will work on our tractors?
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Hi guys: OK, looks like it is NOT electrical, although I really like the idea of switching over to an electronic ignition which I will likely do. I am going to look further into the Onan kit (Thanks Ben!) as well as the possiblity of rolling my own. If I roll my own, I'll post the design, partls list, etc. Anyway, after checking the timing, points, spark plug wires, and coil I changed the plugs. The same problem exists, and the new NGK plugs quickly bult up a lot of carbon suggesting too much fuel. With the engine runnig hot and it doing the ususal apparent misfiring I realized that it may simply be running too rich but no adjustments on the carb made much difference. With the engine hot the intake manifold is VERY cold to the touch, suggesting that liquid fuel is getting into the manifold and is evaporating within it, causing the refrigeration effect. Looks like my electric fuel pump may be forcing too much fuel into the carb. and I may have damaged it. The electric fuel pump I am using is a low pressure model, ~3 psi. Looks like I may have to rebuild the carb. and get a different lower flow pump. (Even though this pump is low pressure it does have high flow - it really pumps the juice.) I will rebuild the carb. and get a lower flow rate pump. If anyone has a part number / manufacturer that is known to work, please let me know.
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TerryZ - I noticed the same cold intake manifold while tuning my CCKB a few days ago. I also have an electric fuel pump and a rich indication (black not gray residue) on the plugs. How about a pressure reducing valve or device downstream of the pump? I've heard of them being used on other engines.
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It doesn't seem like 3 psi would be too much pressure for the carb or would damage it. You might have a dirty or worn needle and seat which is letting too much gas in. Do you still have the return line from the carb or is the pump dead-headed into the carb? Have you checked the choke adjustment to make sure it is opening all the way?
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Hi Jim: I agree, 3 psi should be just fine, but the flow is quite large. I do have the return line in place, and it gushes when the pump is running. I rebuilt the carb about 40 hours ago, new needles, seats etc. I'm thinking I ma getting blow by the diaphragm ---. I will be disassembling on Friday (took the day off to get ready for winter), we'll know for sure then.
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The flow shouldn't be an issue as when it biulds back pressure the flow would decress. If the pump is regulated at about 3psi then you should be OK if the needle and seat are working. You should be OK on any restriction in the orifice in the return elbow since your getting good flow on the return line. I would still bet you have some ignition problem like a bad condeser. You can elliminate the gas/pump problem be putting a fuel shutoff valve between the pump and the carb. Shut it off and run it till it runs out of gas. If it never smoothes out then you still have Ing. problems.
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  • 2 weeks later...
Hi Dave: Well I have not fixed it yet, I had to go to Asia for a week, haven't got back to it. Your idea of using the fuel shutoff is brilliant, will do exactly that. HOPEFULLY I can get this cured this weekend, got to get the blower on for winter!
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