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mackcat12

EM6275L Turbo Lag

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I have a 1988 RD690S With a EM6275L engine was having low power black smoke and high pyro temps, took it to Mack dealer they found a crack in the charge air cooler and said turbo wasn`t working like it should so they replaced it. The truck runs alot better but seems like it has turbo lag. when pulling a hill it doesn`t have the power it use to have. I have changed the air filter and fuel filters and checked the fuel pressure 40psi and checked all the hoses. injectors have been pop tested and all is good, pump rebuilt not long ago. the pyro is where it should be but to me it is smoking more than it use too not real black smoke but dark. anybody have any idea`s what we are over looking? I just dont want to throw parts at it, also this truck doesn`t have a puff limiter it has the robert bosch pump with lda valve and it has a brass fitting coming out of the intake where a puff limiter would be,it has an air line going through it and goes to the lda valve on injection pump, i took air line loose and sucked on the line to see if diaphram in pump is ok. I took the fitting out and it has a spring and ball in it i cleaned it and put it back in. any suggestions would be greatly appreciated.

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mack cat I see you covered the bases, do you know what the manifold pressure is? I have never played with the little engines. is that one a tip turbine? also is the truck equipped with a auto or manual trans? also does the fuel pump lever go into over travel when the throttle is smashed to the floor?

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I found the problem clamp on hose to turbo was broke put on new clamp and all is good now

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Whew! Glad you found it! I had an EM6300L that just did not want to go from day 1. Everybody told me "those new (at the time) 300L's are "doggy",no pun intended! After a checkup at 379,000 miles,the mechanic that test drove the truck (for a different problem) told me that "this is one of the sickest pups I have ever driven". They brought it in and within an hour they changed the diaphragm in the aneroid valve. They said it must have been torn from new! Thing had ALL KINDS of power and still little smoke. Just ticked me off that I had run that long with the feeling that somebody stuck a 5" diameter pumpkin in my stack!

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