sdb89mack Posted January 8, 2012 Share Posted January 8, 2012 (edited) Can anyone tell me how much boost pressure I should have on a 350 E6 . I checked with a hand held gauge against gauge in truck and both are reading 16 psi on a hard pull. I haven't had this truck too long and it just doesn't seem to pull like I heard it would . The vavle train was gone through and re-adjusted. That helped alot but still doesn't want to motivate. Any suggestions? Edited January 8, 2012 by sdb89mack Quote Link to comment https://www.bigmacktrucks.com/topic/22544-1989-mack350-turbo/ Share on other sites More sharing options...
Timothy Maikshilo Posted January 8, 2012 Share Posted January 8, 2012 I had our local "Mack" man of 40 + years remove the barrels on the top of my pump, 1988 350 and remove the springs and "squish" plates. Using a piece of plate glass for a flat surface then with fine emery cloth over the plate glass wet with diesel. Holding the flat surface of the squish plate on the wet emery trace a figure 8 with your hand till any imperfections are removed. This was done to my 1988 350 and it helped performance 100%. Tim Quote Link to comment https://www.bigmacktrucks.com/topic/22544-1989-mack350-turbo/#findComment-97215 Share on other sites More sharing options...
Rob Posted January 8, 2012 Share Posted January 8, 2012 I had our local "Mack" man of 40 + years remove the barrels on the top of my pump, 1988 350 and remove the springs and "squish" plates. Using a piece of plate glass for a flat surface then with fine emery cloth over the plate glass wet with diesel. Holding the flat surface of the squish plate on the wet emery trace a figure 8 with your hand till any imperfections are removed. This was done to my 1988 350 and it helped performance 100%. TimAny idea as to why that would help?Those little "squish" plates are actually the check valves in the delivery valves. If they don't seal as imperfections cause, a portion of the fuel contained within the plunger barrel awaiting next injection cycle is allowed to bleed back into the fuel gallery within the injection pump and return to tank. The plunger upon traveling up the bore of the barrel has to make up this lost volume of trapped fuel and replenish prior to the building pressure within the barrel overcoming the spring pressure of the fuel injector that allows injection. The long and short is too little fuel volume is injected. This is why the power is down, smoke is down, and turbo boost is lacking. \Those check discs and the springs are renewed at rebuild time. I've seen far too many pumps rebuilt due to these valves being bad. Pisses me off that so many shops whosale replace everything in a pump instead of controlling the costs by replacing only what is defective.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/22544-1989-mack350-turbo/#findComment-97219 Share on other sites More sharing options...
Timothy Maikshilo Posted January 9, 2012 Share Posted January 9, 2012 Thanks for the break down Rob, I don't know anything about injection pumps but when our Mack man took the imperfections out the truck went like day and night and didn't need to replace any parts. It was great not having to take the pump off to get rebuilt. Quote Link to comment https://www.bigmacktrucks.com/topic/22544-1989-mack350-turbo/#findComment-97225 Share on other sites More sharing options...
Rob Posted January 9, 2012 Share Posted January 9, 2012 Thanks for the break down Rob, I don't know anything about injection pumps but when our Mack man took the imperfections out the truck went like day and night and didn't need to replace any parts. It was great not having to take the pump off to get rebuilt.Honest mechanic shops are few and far between. A good portion of mechanics are "box swappers" and in some cases need to be as subassemblies are no longer available.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/22544-1989-mack350-turbo/#findComment-97232 Share on other sites More sharing options...
Kav Posted January 9, 2012 Share Posted January 9, 2012 Hi SDB - The two valve 350 go up to about 30 psi in a long hard pull. If your fuel is down or you have some air leaks, it will cut it back a lot.Regards - Michael. Quote Link to comment https://www.bigmacktrucks.com/topic/22544-1989-mack350-turbo/#findComment-97303 Share on other sites More sharing options...
sdb89mack Posted January 10, 2012 Author Share Posted January 10, 2012 Thanks guys for the input. Will tear into it this weekend and give that a shot. Much thanks again. Sam Quote Link to comment https://www.bigmacktrucks.com/topic/22544-1989-mack350-turbo/#findComment-97397 Share on other sites More sharing options...
Rob Posted January 10, 2012 Share Posted January 10, 2012 Thanks guys for the input. Will tear into it this weekend and give that a shot. Much thanks again. SamCleanliness. I can't stress that enough.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/22544-1989-mack350-turbo/#findComment-97403 Share on other sites More sharing options...
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