oldmacktrucks Posted October 10, 2010 Share Posted October 10, 2010 Hi all, I just picked up an 89 DM600 Glider Kit, it has an old (orange paint) 285 2 valve in it. The engine was a pedigree from Mack when the truck was put together in 89. My problem is once the enigine is warm it will start to idle up and down (common for an old 2 valve) but sometimes it will jump almost like you stab the fuel peddle really quick, it never goes over 800 rpm but its quite annoying. It has an AMBAC pump on it and it runs fine anything over 800 RPM's. Low idle is where it is giving me a problem, it does not go low enough to stall but it idles like crap when its warm...any suggestions? Quote Link to comment Share on other sites More sharing options...
HK Trucking Posted October 10, 2010 Share Posted October 10, 2010 The pins & linkage that connect the governor to the rack are worn and sloppy allowing the rack to slide further open, especially if the truck is nosed downhill.Pull the pump & get it rebuilt ASAP, because if the governor linkage comes completely apart the engine will run wild with no control over RPM, and no way to shut it down except to stall it out or pinch off the fuel suction line. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment Share on other sites More sharing options...
oldmacktrucks Posted October 10, 2010 Author Share Posted October 10, 2010 Do I have to pull the whole pump or can I just pull the governor off the back and rebuild it? I hate to pull the pump if I dont need to. Thanks, Sean Quote Link to comment Share on other sites More sharing options...
Rob Posted October 10, 2010 Share Posted October 10, 2010 Do I have to pull the whole pump or can I just pull the governor off the back and rebuild it? I hate to pull the pump if I dont need to. Thanks, SeanI have found it much easier to pull the pump complete and send it in as opposed to remove the governor from the pump while on the engine. The pump can be evaluated properly by the fuel shop when rebuilding the governor also.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment Share on other sites More sharing options...
Kav Posted October 11, 2010 Share Posted October 11, 2010 Do I have to pull the whole pump or can I just pull the governor off the back and rebuild it? I hate to pull the pump if I dont need to. Thanks, SeanHi Sean, If you want to do a quick and much cheaper job, you can just take the governor housing off and replace the bearings and check the kidney weight pins- I have got this done this several times. Most pump shops will only do just that if you take the complete pump to them and will charge a lot extra. As Rob said,if you want to get the whole pump checked out and maybe re-calibrated, then the only way is to take it off and put it on a test bench.Best Regards - Michael. Quote Link to comment Share on other sites More sharing options...
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