I've got a completely stock 1992 D250 3/4 ton heavy duty 5 speed manual trans 5.9L 12 valve Turbo Diesel. My Grandfather bought the truck brand new in 92 and its been in the fam ever since. My Grandfather a few years back toasted the engine when the water pump gave out. He got it overhauled and then put the truck on the farm where it sat for 2 years running maybe 2 times a month. I rescued it from the farm and put new fuel filters and changed the oil, put new brakes and shocks and tires etc.. But ever since the engine got overhauled it hasnt produced any power. I tried pulling my uncles boat and couldnt get above 55mph with the pedal to the floor, and couldnt even shift into 5th. I've had people tell me if a cummins isnt producing black smoke its a fuel problem and others have told me it may be that the waste gate on the turbo is stuck open. Im at a loss here i dont know much about diesels. If anyone can tell me how to do something that would be grately aprreciated. Im trying to restore the truck, and i want a lot of power. I'm an aircraft mechanic so I know how an engine runs and what everything on the engine is, but i have 0 experience on diesels and any advice would be welcome.

 

how does it start on the first start of the day. does it sputter, want to die after it fires, white smoke. sounds like a fuel problem but its hard to tell

 

On the first start of the day it fires right up hot or cold. It doesnt ever crank for long periods, doesnt sputter, doesnt want to die. It does however put out white smoke if i dont press the gas pedal. If i press the gas pedal while i turn the key it produces a little black smoke, and when i rev it it doesnt produce any smoke. But like i said the truck (knock on wood) has never had any problems starting, even when its cold and i dont plug it in, it still fires right up.

 

It may be as simple as throttle travel not adjusted. Truck not running, have someone hold the pedal on the floor and look at the linkage on the pump. It should be hard against the high idle screw. Look at thiss picture but ignore the writing other then the high idle screw.










.

 

It may be as simple as throttle travel not adjusted. Truck not running, have someone hold the pedal on the floor and look at the linkage on the pump. It should be hard against the high idle screw. Look at thiss picture but ignore the writing other then the high idle screw.

I checked the throttle travel and its right where its supposed to be. I did some more trouble shooting and I ended up turning up the fuel pump. That made a noticable difference but it still wasnt produce what i thought it should. so i put a pressure gage on the manifold and got no pressure. I asked around and read a little bit and finally figured out (from what people told me) my waste gate on the turbo could be stuck open. I was told that the turbo would spool up all day long but as long as the waste gate was open I wouldnt get any boost.

 

A stock turbo does not have a wastegate. If it has one someone put it there.

You also will have no boost unless your driving and on the gas. It will show 0 when idle.

 

Well i figured i wouldnt get any pressure sittin at idle, so i just ran the throttle up to almost max, would that be sufficient to get a measurement?.And saying theres nothing wrong with the turbo, then everything seems to be in working order. could it possibly be a bad fuel pump. If not then how can i get power out of it without going overboard with mods and stuff. I also am about to put a 5" straight pipe exhaust on it will that help any?

 

It may have the 21 cm exhaust housing that some of the 92's had and they suck making boost driving, let alone reving with no load. To check boost you really need to drive it so you can actually load the engine. You can get 225 to 240 horses on all stock parts so you don't need to buy stuff till then. Currently you should have 150 or so horses at the wheels on a bone stock truck with factory fuel tune. To check the fuel pump you need to throw a gauge on it.

 

ok cool, thats all the power ill ever want out of this truck, thanks for the info