Jpri Posted May 10, 2021 Share Posted May 10, 2021 I have a 80 Mack 315 hp that loops for the first couple of minutes when started and has a lack of power till it’s driven for a few minutes. Any ideas? Quote Link to comment https://www.bigmacktrucks.com/topic/66678-1980-300-plus-looping-on-start-up/ Share on other sites More sharing options...
fjh Posted May 10, 2021 Share Posted May 10, 2021 Check your throttle linkage for looseness the spring loaded em on the side maybe worn! Try putting some howes or standyne fuel conditioner in the fuel.! Quote Link to comment https://www.bigmacktrucks.com/topic/66678-1980-300-plus-looping-on-start-up/#findComment-473691 Share on other sites More sharing options...
mrsmackpaul Posted May 22, 2021 Share Posted May 22, 2021 Loosing prime and a little bit of air is getting in and hunts until the air is pumped out ? Check the fuel return line for leaks Paul Quote Link to comment https://www.bigmacktrucks.com/topic/66678-1980-300-plus-looping-on-start-up/#findComment-474184 Share on other sites More sharing options...
Full Floater Posted May 29, 2021 Share Posted May 29, 2021 Every old Mack that I have operated has done a little bit of this after a cold start. It's always subtle, but they do it. ALSO, many seem to do the same when accelerating lightly (apparently this is due to worn governer springs in the American Bosch pumps). I do have 2 trucks that do this but run 100% otherwise. I do plan on sending the pumps out at some point to have the governor springs done to see if this corrects the issue. As time goes on and these trucks get older, it may become a more common problem that needs to get dealt with. If I had more time, getting that issue sorted would be much higher on my priority list. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66678-1980-300-plus-looping-on-start-up/#findComment-474480 Share on other sites More sharing options...
mechmagcn Posted June 8, 2021 Share Posted June 8, 2021 Not sure if they even offer it any longer, but there used to be a patch kit that was a light spring that held the rack against the slack in the pump. I did this on my R-Model years ago and it still runs great. Check with a Mack dealer that knows the older trucks or a reputable pump shop. 1 Quote 1971 Mack R600 Toterhome "Superdawg" living the life of leisure pulling 1999 NuWa Snowbird 34+2 SE102 "Dawghouse" Link to comment https://www.bigmacktrucks.com/topic/66678-1980-300-plus-looping-on-start-up/#findComment-474963 Share on other sites More sharing options...
Full Floater Posted June 8, 2021 Share Posted June 8, 2021 4 hours ago, mechmagcn said: Not sure if they even offer it any longer, but there used to be a patch kit that was a light spring that held the rack against the slack in the pump. I did this on my R-Model years ago and it still runs great. Check with a Mack dealer that knows the older trucks or a reputable pump shop. Oh that's great to know about. Did you install it with the pump still on the engine? Im sure MANY a old Mack could use that kit to buy them several more years out of some tires governor spring. Mine sure could Quote Link to comment https://www.bigmacktrucks.com/topic/66678-1980-300-plus-looping-on-start-up/#findComment-474971 Share on other sites More sharing options...
mechmagcn Posted June 8, 2021 Share Posted June 8, 2021 1 hour ago, Full Floater said: Oh that's great to know about. Did you install it with the pump still on the engine? Im sure MANY a old Mack could use that kit to buy them several more years out of some tires governor spring. Mine sure could Yes, install is done with pump on the engine. Years ago I worked on a lot of older R-Models that were bad about loping, even when going down the road, this would stop most of that. If I remember correctly the kit consisted of a lightweight spring, a washer and a roll pin. It goes on the rack at the front end of the pump. I seem to remember that you have to drill a hole in the rack for the roll pin. 1 Quote 1971 Mack R600 Toterhome "Superdawg" living the life of leisure pulling 1999 NuWa Snowbird 34+2 SE102 "Dawghouse" Link to comment https://www.bigmacktrucks.com/topic/66678-1980-300-plus-looping-on-start-up/#findComment-474975 Share on other sites More sharing options...
Full Floater Posted June 9, 2021 Share Posted June 9, 2021 14 hours ago, mechmagcn said: Yes, install is done with pump on the engine. Years ago I worked on a lot of older R-Models that were bad about loping, even when going down the road, this would stop most of that. If I remember correctly the kit consisted of a lightweight spring, a washer and a roll pin. It goes on the rack at the front end of the pump. I seem to remember that you have to drill a hole in the rack for the roll pin. I will soon attempt to contact Mack to see if this kit can still be had, if I find it; I will report back with a part number. Quote Link to comment https://www.bigmacktrucks.com/topic/66678-1980-300-plus-looping-on-start-up/#findComment-474999 Share on other sites More sharing options...
BOBWhite Posted October 11, 2022 Share Posted October 11, 2022 Any updates on this? Been looking for a fix for this and never heard of this kit. Quote Link to comment https://www.bigmacktrucks.com/topic/66678-1980-300-plus-looping-on-start-up/#findComment-511524 Share on other sites More sharing options...
Full Floater Posted October 25, 2022 Share Posted October 25, 2022 On 10/10/2022 at 9:05 PM, BOBWhite said: Any updates on this? Been looking for a fix for this and never heard of this kit. No updates on my end. I have several engines that could use this. I just simply haven't looked any further into it 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66678-1980-300-plus-looping-on-start-up/#findComment-513484 Share on other sites More sharing options...
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