new kid on the block fuel question

[Riley]

Hello all,

New to this site. I just purchased an 1987 Ford F250 with the 6.9 engine. It has good power, but blows lots of black smoke when accelerating and climbing hills. The truck came from low elevation, I am at about 4,000 ft elevation, and will be using the truck quite a bit at 6,000 to 10,000 ft elevation.

My question is about the fuel adjusting screw. There are excellent instructions here about adjusting it for increased flow. I want to decrease the flow.

This afternoon I turned the screw down (counterclockwise) slightly, like from 12:00 back to 10:00. That did seem to help with the smoking, it smoked less and it was not as dark black.

Can I turn the flow down more, and is there any problems I will run into if I do decrease the fuel flow a bit more?

I am new to this type of diesel, so any information is much appreciated.

 

[Russ]

You can turn it down. Most turn the screw UP two flats when adding a turbo, but your losing air with the high elev. so I would try turning it down two flats. You will lose some power, but excessive black smoke is wasted fuel anyhow. OR add a turbo and enjoy.

 

[Michael Fowler]

Or you could use less "gas" pedal. Remember that diesels are not throttled; they are wide open to the atmosphere. You control the amount of fuel by the "gas" pedal.

 

[Riley]

Thanks for the quick replies. I will turn the adjusting down a bit more tomorrow. I have been letting up on the pedal, but was still rolling quite a bit of black smoke. To get to my place I have to pull 5 blocks up a very steep gravel road, and even barely moving, I was still putting out a lot of smoke. I noticed with the first adjustment I made today, it make a big difference in the exhaust when pulling up this hill.

And the turbo is a very tempting idea, but I will only be driving this truck 2-4000 miles estimated a year, so the cost is hard to justify. I am getting some prices though.

I'll see how the truck and I get along for a while before jumping into the turbo probably. I would welcome suggestions for improving air flow though. This truck has the stock air filter system as well as the stock exhaust. As we say when hunting up on the mountains, there's lots of air up here, just darn little oxygen! I'm sure anything I could do to increase air flow would help the engine at the higher elevations.

 

[Diesel JD]

Well, on the fairly cheap you could deep six the stock 2.5" exhaust and muffler and get a 3" with a free flowing muffler of some kind and if you still have the "soup bowl" in your air intake you could cut that out. These trucks which were sold for high altitude applications came from the factory detuned(IE fuel turned down) to control smoke and EGTs the bad news was they were rated at around 25HP less than the sea level models. Having more fuel does no good if you haven't got the oxygen to burn it as you found out. The turbo is the best mod for these trucks but the cost is very hard to justify for a very little used vehicle. Mine got it because its my daily driver and I happened to have the money hanging around at the time. Its the best thing I did for the truck and the 2nd and third best things were the manual tranny swap and the 4" no muffler exhaust!

 

[RLDSL]

Advancing the timing a bit should help as well. If you have access to timing tools, try about 1 -1.5 deg. If no timing tools available try just advancing the timing a nudge( mark with scribe where it is now , then advance about a dimes width ) and see what happens

Cutting fuel volume back and advancing injection timing is the standard method for tuning diesels for altitude.

 

[Riley]

I really appreciate the information from you guys. Although I have operated a lot of diesel equipment over the years, I have zero experience with this engine. But I just couldn't pass up this cream puff of a truck, (It apparently spend most of it's life in a garage) and the poor seller was in the middle of a nasty divorce to boot.

So here we go. I appreciate the tip on the "soup bowl", no idea what that is but when I look at the engine in the morning I will probably spot it. As far as advancing the timing, I did assume I would need to do that but haven't had time to figure it out yet. I imagine the information is on this web site somewhere.

I'm not surprised at the drop in HP in the diesel engine at this higher altitude. I used to travel a lot for work, and noticed a dramatic difference in power and MPG at lower altitudes with gas engines, as much as 25% to 30% improvement at low altitudes.

 

[LCAM-01XA]

Riley, if you look at the are where the injection pump attaches to the gear housing you will notice there are two studs that hold it to the housing, there is another one as well (so they essentially form a triangle bolt pattern) but it is under the fast idle solenoid on the passenger-side of the pump and thus near impossible to see from up top. To advance the timing you need to loosen those three studs (well, their nuts at least), then turn the injection pump a bit towards the passenger-side fender, which would be clockwise if you're looking at it from the cab, and CCW if you're looking at it from the radiator. If you're lucky on the front face of the IP right near the gear housing mounting flange there will be a big fat tab sticking out, and you will be able to slide a 19mm (or 3/4") wrench on that and turn the pump this way. Only adjust the pump with the engine NOT running. And as RLDSL suggested, draw a mark on the IP mounting flange that also extends on the gear housing flange, this way when you turn the pump you'll know how much you're turned it.

 

[Diesel JD]

Good call RLDSL and Ivan, you have to have those reference marks and know what way you
re turning the thing to have a chance to get it right.

 

[Michael Fowler]

Those nuts on the IP are difficult to get to. I am not sure if there is a special tool made for this, but many of us have modified 9/16" box-end wrenches to make it easier. The mods to the wrench include thinning the wrench for about 2 " from the box end, and then putting in a little offset to better clear obstacles.

 

[RLDSL]

Those nuts on the IP are difficult to get to. I am not sure if there is a special tool made for this, but many of us have modified 9/16" box-end wrenches to make it easier.

Yes, There is. OTC tool #303-227
I picked one up off the snap on truck for about $80 Should be available from fords tool distribution by calling 1-800 ROTUNDA ( which rings through to OTC tools ) Price would likely be even more.

Very handy wrench though, worth the $$ to save time bent over the fender

 

[LCAM-01XA]

Actually I've had great luck with a regular open/box-end 9/16 wrench made by Kobalt (Lowe's brand) - getting to that pesky nut under the fast idle solenoid wasn't much of an issue in my truck, then when working on Jake's 6.9 I first tried one of his Craftsmans and it wouldn't fit, got my Kobalt and it was pretty much a breeze - gotta take the time to adjust it on the nut obviously, but still fairly easy. Oh, and I usually climb on the bumper and reach over the radiator and the fan for those nuts, or sometimes even climb inside - I'm a small guy tho, 150lbs, I can pull it off without breaking or bending anything. One of these days I gotta make me a bumper step like Jeremy has, that would make engine work sooo much easier...

 

[Riley]

After a lot of adjusting, a bit at a time, I think I have the fuel adjusting screw set about right. The power is about the same and the exhaust is about 80% less than it was. I ended up turning the screw over 180 degrees finally after several adjustments and a lot of test drives.

I did try a small adjustment in advancing the timing of about half the thickness of a dime, but that caused a bit of a miss or hesitation when pulling the steep hill to my place, so I set it back to the original setting.

Regarding the air flow to the air filter, it is the original setup with the long plastic tube running to the front of the grill for intake. Just looking at that setup, it seems it would be somewhat restrictive. I wonder if it would help the air intake to unhook that long tube? I would appreciate any thoughts on that. It does also have the original 2 1/2 inch exhaust at present.

 

[LCAM-01XA]

I have my intake open like that, I cut the pipe just before it the wide part of it ends, so I now have the full 4" opening available

 

[RLDSL]

If it started complaining when you advanced it, it sounds like it's already been advanced. Timing should be good .

That stock exhaust is highly restrictive, not to mention that the factory muffler is probably pretty clogged with soot by now ( when I first put my turbo on, it wouldn't build boost, I cut the factory exhaust off and the muffler was so clogged that I couldn't lift the thing. Opening up the exhaust made a huge difference ) Chunking it and running a 4" pipe and straight through big truck muffler would help a bunch. All the busses and dump trucks that came with these things came with 4" or better from the factory.