Good to be posting here again. I know there have been a lot of threads on this subject, but I havnt found much on the various subtle signs that an injection pump is bad. One time I had a pump that was tested by a trusted diesel shop and it tested good. But in actual driving conditions was very inconsistent. On a very hot day it ran rough and had very little power and occasionally go smooth and run great after hitting a bump in the road. Just one example. The motor I have now does not smoke no matter what you do. It idles a little rough and rocks back and forth some. My timing meter broke, so I played with the timing a little. If I rotate it advanced almost to its limit, will not smoke. If I have it far retarded, will not smoke. In fact, it doesn't seem to change the way it runs much if at all, and I've listened to these motors for a long time. But other times it will make a difference. Today I left it way on the advanced side and it ran fine but seemed to lack something as always. Didn't sound quiter like other times when I've had these motors advanced too far. You could feel the truck shake a little. I just drove back from work and the motor is quieter and doesn't rock the cab like it did before. What I can't figure out is why it doesn't smoke! Regardless of what I described above, it will not smoke. I want a sign that tells me I've changed something, but I get nothing. I'll gun it and shove my foot to the floor and no smoke. I've tested it with the pump timed every which way. I even pulled a steep grade locked in overdrive going 60. Temp got up to 210 on the gauge and there was a little bit of smoke but not much. Didn't seem to be underpowered but it wasn't exactly pulling it easy either. This is in a light bronco. I have never tried so hard to get a diesel to smoke and failed like this. Either this is the cleanest burning motor ever built or my injection pump is doing something odd. What do you guys think?

 

Motor is a 1989 7.3 non turbo. Heads are rebuilt. Bottom end is good, bout 200,000 on it. Injectors are new, injection pump is older but don't know anything about it. It has an electric fuel pump instead of the mechanical lift pump. No air intrusion, no fuel leaks on return lines or anywhere else. No water getting in the fuel. I can't think of any problem that would prevent it from smoking...

 

Soooo... you WANT smoke? Or you want to know why you can't get anything other than a clean burn even with timing being off?

 

The latter. Since I can't time it I wanted an idea of where I'm at. But the beast won't smoke. Not so bad I guess. I've just never had one burn so clean. The pump seams to have some difficulties according to temperature, just thought that running issues and timing would come out as smoke. I guess I might be complaining about having a motor that works fantastic! But I still expect to see smoke. Makes me think the pump isn't working right if I can't throw the timing off enough to get some smoke. Maybe I don't understand these pumps enough.

 

No, I think you're on the right track with that one. Most would agree that the proper tuning for an IP would be that at WOT it should smoke a little. That means you're getting enough fuel through the fuel screw. I think you might open yours up and turn the fuel screw up a little. Every pump is different.

 

That's what I was considering. Maybe it's a 6.9 pump or it was set too lean? Turning up a tad wouldn't hurt it.. Think I'll try it!

 

6.9 pump won't make a noticeable difference. Do you have a good fuel pump to the injection pump? If you have the funds install a pyro and crank the fuel screw, timing will be more important with the fuel cranked though.

 

Well mine does smoke at wot but its a new one and havent been able to get timing meter yet. I did hit 16.9 mpg at fill up but noticed fuel dropped 3 gal at 28 miles. Found line leaking. But to answer your question with my old one it smoked all the time and had less and less power. Top speed at the end was 45-50. So that being said. I've also replaced injectors and gp. And I agree with others that you are on track to find that sweet spot.

 

A *good* 6.9 pump will perform just as good as a 7.3 pump, even with a turbo and being able to use extra fuel. A *bad* pump won't perform, no matter the type.

I'd make sure A, you're getting good pressure /to/ the pump. Then crank that fuel screw in.
Pyrometer is nice, but you can roughly tell the temps without it - when you are smoking, your temps will skyrocket quickly(I'd say 60sec max to be safe in this condition). If you're pushing the engine at full load(that is, more pedal = no more acceleration) you'll get high temps. Don't run it like this without a pyrometer very long. If you've still got some extra acceleration(part load) left in the throttle, you'll be fine temp wise.

Remember that the fuel screw only changes the /max/ amount of fuel in at full throttle. It won't add more fuel to idle, or part load - it just means that instead of 'running out' of pedal earlier, the pedal still does something... but if you add too much fuel you get smoke.