89 has become a real dog

[WBegraft]

hi i have an 89 cummins that had tons of power about 6 months ago but its slowly died off just recently its become hard to get it going over 60 on the highway it use to to about 80 with ease i have checked and replaced all the obvious like filters checked timing new lines from the tank they had pin holes in them and the fuel would bleed back down over time making it hard to start i also changed the lift pump its only getting about 12 mpg i ruled out the turbo i rebuilt it and it also doesnt smoke i figured if the turbo was bad i would get some smoke from all the fuel with no boost it seems like its lean because it never smokes except a little bit at startup but no little puff of black when you get on it like it used to oh yeah the injectors are new also and the truck is stock with a little under 300,000 injector pump is about 100,000 old please help before this truck drives me crazy thanks Bill

 

[ARhine]

do you have any boost or pyro guages?



Maybe a stuck AFC pin?

blown boost boots?

Hole in intercooler?

 

[WBegraft]

no i dont have any gauges im gonna get em but that doesnt help me right now

 

[Greenleaf]

Yes sir. Open up the top of the pump (AFC). Remove the cover from the AFC and pull the control cone out. Look-see at the fueling pin that rides on that control cone profile. It could be st. . st. . st. . st. . sti... ... . sticky.



Two things; With it removed, cycle the throttle quickly. It "may" pop out if it's free. If it does not, do not panic. I have started the engine allow the fuel pressure to work it out. I have used light oil to help with a sticky pin, while the engine was running. The internal force of the gov link against the "reverse" lever will push the pin put while I try to push it in with the cavity partly filled with oil.



You can also disessemble part of the pump to get to that lever/pin assy.



You can assemble with grease to check for a "witness mark"



This is tough to explain unless you know what the parts are and how they function, normal or otherwise.



More than one way to do all this... ... ... .

 

[WBegraft]

i checked the pin its moving i cleaned it up in there it was some grease or varnish on that cone though but it didnt make it run any better i'm gonna go back out now and keep messing with it but any help is much appriciated thanks

 

[ctd8999]

Check to see if the throttle cable is making the pump lever go to the full open position. The cables do stretch. Thanks Steve B

 

[WBegraft]

i checked the linkage it was good we fixed that a while back with some new ball sockets but thanks for the suggestions i know someone will hit on that one thing i havent thought of yet anyone think maybe the inj pump is dieing what r the symptoms thanks again