Ok, I've been working a lot of bugs out of this truck, and I think (knock on wood) that I've got most of them. But...I really think that this thing should have more power than it does. It is a '93 F350 dually, 7.3 IDI. It has about 182,000 miles. It (now) starts and runs smooth, thanks to new GPs & GP controller, fuel return line kit, new lift pump and fresh fuel filter. I had both bad GPs and air induction problems that were making it hard to start that I think I have now resolved. The starting problems (or resolving them) didn't seem to effect performance for better or worse. Now I want to work on the power issues (or lack thereof). It is a 17' rollback tow truck. As far as I know, most everything is stock. The air filter is a standard paper filter, but I have tried running it with the air cleaner removed and I didn't see any difference. I can not put the pedal down more than about a third of the way to the floor, at any speed and in any gear, without it pumping out a ton of black smoke, and no, it doesn't smell sweet. It won't accelerate any faster once it gets to the smoking point. Loaded or unloaded doens't seem to make a big difference either. Any slight hill and I'm downshifting (5 speed manual) and losing speed. I know that this thing is never going to run like my '03 6.0, which can haul a load up the mtn and act like nothing is there, but I can't believe that this is the best that this old work horse can do.
I haven't run Diesel Kleen through it yet, so that will be my next step. I suspect that a bigger exhaust would help. The pipe that is on it looks like it is about 2.5", so I was considering a 3.5" kit from Hypermax. But, that kit looks like it starts behind the Y pipe. Do I need to start at the manifolds, or would a 3.5" pipe from the Y pipe back help? BTW, with the 17' rollback bed, the wheelbase may be longer (it has a three piece drive shaft) than normal, and thus the exhaust pipe longer too, which I suspect might be contributing to exhaust flow restriction. Also, I am in the mountains of CO, so I am running at 6 - 8000' above sea level...I'm sure that doesn't help, but running w/o an air cleaner/filter on didn't make any difference.
I am not looking to add a turbo, but might do some ram air mods if I thought that they would help. I would also consider LPG, but I want to try to get the most out of this old dawg that I can before I start adding a bunch of expensive mods.
Give me some ideas, 'cause I just can't believe that pushing the pedal 1/3 of the way to the floor is the limit!
The black smoke is because someone has turned up the fuel to much, It should be turned down till it no longer smokes black.
Black smoke = Unburnt Fuel (No Power Gain) = Fuel wasted!
At that altitude you are going to be suffering for power without a Turbo, It really needs one.
More air = More Fuel = More Power!
There is nothing other that will make any real noticeable change.
If your going to spend the bux on the 3.5 exhaust it needs to include a better Y... The Y is the biggest restriction on the system.
Don't expect the butt dyno to feel it though!
You money is best spent on a turbo. You should look at a hypermax kit!
This truck wont be leading the pack with a load, without a turbo and especially in the mountains......you need a turbo.....mostly because you are used to a more powerful rig!!!
I never see black smoke except for when I ran my truck in the mountains in CO (up to 10,000ft).
Being a tow truck, I would suspect it has had it's share of idle time along with that 182,000. The injection pump and injectors are likely needing to be replaced.
Along with the over fueling, the advance on the injection pump is likely very worn.
Wondering if the IP wasn't turned up, rather needs to be adjusted to this altitude (VA truck until recently)? What's the difference between having the IP turned down vs. backing off of the pedal? For what this truck is used for, don't want/need to go to turbo, just want to get all I can out of what it has. Is there any way to check the IP advance wear and/or the "need" for new injectors before replacement?
Also, any ideas on finding an exhaust kit that includes the Y pipe? I don't see the point of an exhaust that still has a bottle neck at the Y. Any thoughts on that length being an issue? If the length is part of it, would a 3.5" from the Y back at least help there, if I can't find a bigger Y?
Any place that makes exhausts can modify the Y pipe to remove the Y bottle neck.
The big thing is where both down pipes come together.
I cut mine apart so they dumped into 3" pipe instead of staying the same size at the rear of the Y and it did help some.
Given the Va. truck until recently, the fuel and timing is probably set for much lower altitudes since most of Va. is below 1000 feet.
High altitude motors had slightly retarded timing and lower max fuel delivery.
Turning the IP down just drops the max fuel delivery rate.
And yes, letting off the throttle does the same thing.
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86 F250 HD 6.9 IDI ATS turbo "not exactly" stock 4x4 T19 BW1345 3.55LS both ends D60 front, 10.25" Sterling rear, ram air, dual stacks.
Ok, so in order, I will do; Diesel Kleen, timing, injectors (?), exhaust system, high flow air filter, IP pump adjustment if still blowing black at this point and/or replacing the IP pump. Does this make sense, or am I missing something logically?
BTW, the injectors appear to be original, based upon the paint color on them, so I'm inclined to focus there. But again, is there any way to tell when they truely need to be replaced? I hate replacing things just to see if it makes a difference.
If there is an injector shop around you, they can test the injectors for psi and spray pattern. They should know the specs. If you are a tool guy you can build your own pop off tester, with a lever operated hydraulic and pressure gauge. See how much that test (or tool) would cost, compare to $20-25 a piece new at Great West Fuel Injection (gwfi.com) or Pensacola.
For the money and peace of mind, might as well just put in new. Unless you like tinkering, which is fine and well.
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1989 7.3L E-350 based Wheelchair Transit bus converted to Recreational Vehicle.
Dave, I just want to make sure my understanding of things is correct. In a reply on another thread, you said "If you are blowing black smoke, you already have more fuel that you have air to burn. More black smoke is just wasted fuel, not more power." Would it not be more accurate to say that if you are blowing black smoke, you have inefficient combustion? More specifically, would bad injectors cause black smoke if they are not atomizing the fuel properly? Thus the problem would not necessarily be too much fuel per se.
I want to clarify this because I am working on the theory that my black smoke issue is not simply because as Festus said, that someone turned up the IP too high. Rather, I am working from the assumption that some thing(s) have happened; age, wear, environmental changes, etc. that have resulted in poor perfomance. If, after eliminating as many of these possilbe performance killers, I'm still blowing black, then I'll look at turning down the IP.
If you have 182 K on the clock, you are overdue for new injectors.
Given the cost of new injectors here lately, I would go with new instead of having yours rebuilt.
Somewhere in all of my data, I have the air pressure drop for each 1000 feet increase in altitude.
But without even finding the exact drop, I can tell you that a diesel set up in Virginia has way to much fuel for running at 8,000 feet even at stock factory levels.
And my guess is the fuel was probably set a bit higher in Virginia trying to get a bit more power.
Also I don't know if you are close to Denver, and I don't know if they may have used or rebuilt turbos for sale, but ATS Turbo is now located off Ward Road in Arvada now.
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86 F250 HD 6.9 IDI ATS turbo "not exactly" stock 4x4 T19 BW1345 3.55LS both ends D60 front, 10.25" Sterling rear, ram air, dual stacks.
When you say leaking injectors, do you mean internally leaking, or externally? With a new return line kit installed, everything externally is dry as a bone.
Diesel Kleen has now been done, without any significant improvements. Might be a little less smoke, but if so, its not much.
Festus, how long will they stay wet after being run? If I am pulling them on a cold engine, will I still see wet tips if they are leaking, or does the engine have to have been running more recently?
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