A few weeks ago i bought a 86 ford f-250 4x4 6.9 n/a diesel, 96000 origanal miles. ok my question now is as i was driving it home i noticed it smoked alot of black smoke i mean alot!!! when you take off it puffs a huge cloud out and you can be goin down the road in high gear and stomp it and it will take off rollin black smoke out. And it has more power than my 89 7.3 n/a. now here is the funny thing it gets 18 mpg. I no that sounds unreal but it is not i have checked it three or for times, it has a few modifications done to it that i can see, it has 2.5 inch dual pipes from the manifolds back to the rear axle where it goes into dual flowmaster mufflers right before it goes togather into a single 3inch pipe then turns out behind the rear tire. And the other mod. that i can see is it has the soup bowl cut out. And i have one last question it was 17 degrees the other morning the truck was cold been settin two days got in it turned the switch on let the glow plugs heat up one cycle, it didnt turn over but three maybe four turns and it fired right up no problem, my 89 7.3 would have to have either sprayed in it to crank that cold. why does it crank so good???

 

Sounds like the truck was maintained very well, the 6.9 has higher compression maybe that will account for it starting a little better under colder conditions, but I would imagine everything is working good including the glow plugs and controller, as well as the timing being set just right.

 

it has been very well maitneced, it is one of the cleanest diesel engines i have ever seen the body aint beat up its pretty nice, i got it for 900 dolars. just had to put a passenger side window in it and a universal joint. so all the black smoke that it rolls out is normal i know my 89 didnt never puff black smoke unless you lugged it really bad.

 

Sounds like someone has turned the pump up quite a bit, does it have a pyrometer? I am not sure I would hold into the throttle too long if it doesn't. Sounds like you got a really good deal, I have been noticing around here that with diesel staying over a $1.00 more a gallon than gasoline all these old diesel trucks are starting to get really cheap.

 

it does not have a pyrometer,but im going to get one, and i was thinkin it might be turned up cause i think it has way too much power for what it is. i got a stock 89 7.3 and my 6.9 will run circles around it. and im going to try to keep my foot out of it until i get a pyrometer, but it still gets 18 mpg thats what i dont understand, my stock 7.3 gets 12-14

 

That could be gearing or the condition of the IP and injectors.

There are a lot of factors that affect diesel MPG.

As for the starting, are the glow plugs all good in the 89?

 

brand new glow plugs and brand new controler in the 7.3, as for gearing the 6.9 has 3.55 and a t19 4 speed, 7.3 3.73 and zf5,same 33 inch tire size, 6.9 96000 origanal miles and a few little mods not sure if they help not sure why it smokes like a freight train but it has alot more power than 7.3 and alot better milage not goint to mess with much on the 6.9 till i find a good used turbo for it. 7.3 not sure how many miles it has but it hates cold weather. 6.9 at 17 degrees engine completely cold cranks like 7.3 when its 80.

 

and one more thing i forgot to mention when the timing advace is on it has a power stroke rattle