Mcrafty1

I'm practicly computer illiterate and haven't yet figured out the picture posting thing but I do know that My business is on Google and if you follow this link...https://allanhanscomconstructionexcavation.workingpoint.com/they have a picture of my truck there. I have no idea how it got there but its my truck for sure. When I figure out how to post pictures I'll put up some myself. (or I'll get my grandaughter to do it for me )

Yes the spray nozzles where ruled out earlier, Thanks for the reply

You done great explaining what you meant to, but that doesn't explain how that could happen, if all injectors are being feed from the same pump...and the pump has been calibrated and known to be accurate, the air is being driven into the engine with the same turbo and the cooling system is working as designed and the water temp never exceeds 200 (very rarely that high) then what could cause the same piston (hole) to burn two pistons to the point of breaking the ring ledges and the other five out live that one by now 2 x's (the original piston after the rebuild....another after that and another season on all five of the others on top of that. That is why I'm scratching my head, I appreceate your input too, thanks

I agree with everything you say, The pump WAS calibrated when it was rebuilt......the only thing I changed the last time around was the piston, rings and sleave AND a new injector, I did the injector change because I suspected the spray pattern was bad, That being said I have run the truck one season since I made this change and so far so good. The only way to know for sure is to pull the head and have a look. I'm not going to do that...oh, and the timing was checked too so too much fuel COULD be a problem but that really don't explain why it's the number 6 hole both times and the EGs staying within spec. It is beginning to be a head scratcher at the moment.

I'm in touch with the rebuilder and hope to findout something soon, if I cant I'll have it done before I start using it this spring. Thanks for the reply.

I don't know that they did any flow testing, I'll have to check and see, thanks for the help....both you and Glenn, I hope to get to the bottom of this before anything happens to this engine. This should help me do that.

Last time I had mine gone over it was around $1600.00 The pump was worn pretty bad though and in need of an overhaul....This is on a 250 econodyne.

No scoring, just melted down over the edge of the piston to the point of breaking the ring and then the ring ledge......the pump was completely gone through when the engine was rebuilt two pistons ago.....and the timing was checked when the engine was rebuilt and possibly when the first piston was replaced....the second time the piston was replaced and the injector in the same hole was replaced but nothing else was done. The fuel is maxed out but as I said in my OP I am very careful of heat, My concern is the fact that its the same hole each time so the over fueling in that one hole is deafinatly a possibility I'd not considered......However I take your an anyone elses info and advise to heart and appreceate any and all input.

Hello all, As stated I'm the new kid on the block. I own a small earth work business in the great state of Maine and own an 1986 Mack RD685S that I use as my primary truck (its my only truck at the moment) and at my age(59yo) I hope to 'finish out" with it. Its a great piece of equipment which I've owned for a dozen years or so and built up to what I have now. Looking forward to reading about and hearing from thuroughbred Mack owners and all others about thier experiences over the years with these truck and will throw in my 2cts when I feel it will contribute to the mix.

Hello, I'm new to the forum.....I have an 1986 maxidyne 250 four valve engine and have (twice now) melted the rear most piston at the ring ledge Same hole both times? the second time I changed the injector although all tested out ok, this was the beginning of last construction season and thus far the problem has not risen its ugly head,,,,, I have a pyrometer and have always been very careful not to exceed the 1050* heat max. and would like some input into this...also like to know if anyone else has experienced this problem....oh, it was an econodyne engine and I did open the fuel up on it a while ago (before the first meltdown) which I don't believe is related...I've been wrong before.