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post #30 of Old 05-15-2012
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Re: Runaway Yanmar 2qm15 HELP!

Great discussion. Miami, hope things get sorted out for you, and the re-timing solves your problems.

A couple of comments based on my own experience with my 2QM15 last year...
First, those shims under the top of your fuel injection pump are critical to its proper operation. If it's shimmed too low, the stroke will be way too long on the pump and it will pump a LOT of fuel at idle. My installed engine's pump has three shims stacked under the top. My spare engine has two shims. Total thickness is 15-20 mils, but that is a high percentage of the total stroke on the pump. If they have been tossed, and not reinstalled, you need to replace them with enough stack height to get the engine back to idle speed with the throttle at idle.

Second, the governor attachment to the fuel injection pump is a PITA and you gotta make sure to get it done right. When I replaced an injection pump last year, it took me about three hours to sort how to hook it up and get it hooked up right. The rack on the pump is a finely tuned, low friction mechanism and if it isn't exactly right, the throttle control and governor will bind, prevent throttle control, and could cause engine speed to run up to max. If I hadn't had the tech manual to puzzle over, I don't think I would ever have gotten it hooked up right. You can't get the governor connected to the rack properly without the top of the fuel injection pump lifted, and you have to settle the top of the pump into place with the rack and governor in the proper position. Once they are in place, you can tighten the top of the pump down, being careful that the governor-rack orientation doesn't shift. Also, did you check the rack adjustment for maximum "throw" and make sure it was properly set?

Won't take but a few minutes to pull the governor inspection cover and check out the governor and injection pump rack. Move the throttle through full throw and see that the mechanism pushes the fuel rack forward smoothly, and that it returns when the throttle is released. I know you had to have the cover off to reinstall the injection pump (didn't you?) and get it hooked up when you replaced the pump, but it might be worth another look.

Good luck.
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