How much fuel with stock injectors?

[sparks57]

I'm about ready to tune my pump up quite a bit. I know you can't put too much fuel in when you have stock injectors so you're not too hard on the pump.



About how much can you turn the fuel screw down from the stock position without damaging the pump with stock injectors?

 

[sparks57]

Looked back through the archives and found two statements.



One said 1 turn, the other said 2.



So which one is correct?

 

[sparks57]

Also, for all you guys who have experience with this:



Can you give me some tips on optimal settings of the injection pump with stock injectors?

 

[Greenleaf]

Hey CB, I turned my pump one and one half with the factory units still in place. I didn't notice any gain in smoke or the "seat of the pants" feel. I installed a 16cm housing and this one mod was the largest contributor to boost and response hands down. That was until I installed the POD's/performed pump mods.



What you are suggesting won't have an effect on pump life span unless you begin using the pump beyond what you normally have been doing. I. E. drive truck to work/school/video store... ... . then turn it up two turns in,now pulling a 30 foot trailer with a John Deere 820 Diesel up top (had to get my dibs in here) At this point you are working the pump to the point that it is now "using" that extra fuel to move the load. However, at the same time, the stock injectors can't flow enough fuel to overcome the load placed on engine so the engine slows further under load and the gov says to the pump "push more fuel still!" But your injectors refuse to cooperate. Now you'r stressing the internals of the pump.



Clear as mud, right????



Greenleaf

 

[sparks57]

I do pull trailers every once in a while. Max trailer weight so far was bout 5 tons of hay on a triple axle trailer.



But, 99% of the time I run empty.



I'm lookin' for a 16cm housing if anyone has one. I've heard they make a world of a difference.

 

[formula]

Given that you have an intercooled truck... ... You will gain more power by just installing bigger injectors than you would by turning up the pump with the stock injectors. It's easier on the pump too. So, do ya feel lucky... ..... well, do ya?



Sean

 

[sparks57]

True, and I would really like some EDM injectors, but there is no way I can spit out $700 for a set any time soon.



Especially being that I may have a dieing injection pump...

 

[Bob Beauchaine]

You may not get any noticeable performance improvements by turning up your pump with stock injectors - this is not all that unusual with a 1st Gen in stock form. My first mod was a Banks kit with a 14cm waste gated turbo and a 3. 5 inch exhaust. That setup felt good but I'm willing to bet it didn't add that much RWHP - it just felt better. When I added Bosch 185s things started to happen. You can look at my sig to see my current mods. It does get addictive and fun!!!



Bob

 

[dpuckett]

CB-



1) What makes you think your pump is dying? Could be timing just got slipped back through geartrain wear over the miles. 1 degree slip can make a big difference in starting, running, etc. Or you could just be getting used to it and need to add more fuel and air- that seems to be a common problem here.



2) On my 1st 93 [W350 CC alum flatbed, 5 speed, 4. 10], I could get the clutch hot empty drag racing Chevies through town- clutch had 3K on it when i got it. Point being, I have had good luck with tweaking a pump with stock injectors. I had the AFC tapered pin at about 75%, Full power screw in about 1. 25-1. 5 turns (it was 3 years ago I got it, memory already getting fuzzy). This took me from a peak of 16 psi to a peak of 23-24. Still had the 18 cm housing, stock H1C, straight stock exhaust. AFter I got the injectors cleaned and recalibrated, I went from 15 mpg to almost 19 mpg in town; 20 hwy.

I'm getting my first set of aftermarket injectors this week, hopefully- Rip says UPS is dragging its feet, so it may be a while.



Daniel

 

[sparks57]

Check out my post about "injection pump woes".



I'm glad someone had good luck, I was starting to get discouraged...



At the same time, I plan on throwing on a 16cm housing, and doing some porting/polishing.

 

[MSilva]

The 16cm housing and turning up the pump modestly helped my acceleration quit a bit. Installed pods today and the truck smokeslike coal burning locomotive and tons power. I am

afraid I might break something at wot.

 

[Greenleaf]

afraid I might break something at wot

Well said... . one of the reasons I put the truck up early for the winter.

I was really surprised to find that the mods done to my rig have turned it into more of a top fuel dragster than what I was expecting. In fact the last time I had it out on the road I literally scared myself. The last thing I need now is to wrap it around a tree/arrested for reckless

op. Not sure how long the stock transmission will hold out at WOT.



I read somewhere that you "better have it pointed where you want it to go when you hammer the throttle" rings loud and true for me.



Scott

 

[cerberusiam]

CB, I ran my fuel screw at 3+ plus turns with the pump already going and drove the snot out of it for 30k before it died completely. That said, you may turn the screw 1 turn and it will die tomorrow. If you have over 100k on the pump there is no way to tell what is too much. I have seen newly rebuilt pumps die with less than 20k when pushing a lot of fuel thru stock injectors. Your rolling the dice either way. I know your dilemma, been there.



Talking to several pump builders about how much is too much for stock injectors generated a consensus 10 to 15 percent will not significantly impact pump life with stock injectors. When you get to 20% the curve steepens rapidly. What that translates to turns on the full power screw is dependent on how good of shape the pump is in so it is a guess.



My truck is relegated to dump runs and short trips due to testing the how far to push the pump and injectors. It ran as good with an H1C and 21 housing as it does with the HX35 and 16 housing. Unfortunately it ate the turbo and is in the process of chewing the trans to pieces. :{



My advice, drive it the way it is until you can afford to fix what your right foot breaks. Cummins Power is addictive! Good luck.

 

[sparks57]

I think I'll just play it safe and stick to 1-2 turns for now. I'll be getting new injectors within the next few months anyways.

 

[JLEONARD]

One of the reasons I haven't touched my fuel screw is pump life.

I've rotated the eccentric , played with the starwheel, ground some off the plactic ring, but that's as far as I want to go.

I really need to dyno to see where I'm at. My only dyno experience to date was with just the K&N and 16 cm housing.

And since the Pastor ruled against me so windictively I have to start from scratch.



E C Jay

 

[Greenleaf]

Word of The Day:

windictively

 

[sparks57]

I think he meant "vindictively" which means "out of revenge" or "spitefully".

 

[Greenleaf]

Thanks

I wouldn't have known what "vindictively" ment either

 

[sparks57]

Looks like someone didn't pay attention in english class!!!

 

[JLEONARD]

think he meant "vindictively" which means "out of revenge" or "spitefully

I made no speeeling errors. I started to type as above, but I didn't really mean "out of revenge" because I know Bob didn't mean it that way , so I changed the "Vind" to "Wind" because our Pastor made a big sermon out of it!!



Straight out of Webster's 5. 9L6BTA edition:



Windictively... . (adverb) used to describe how a pastor of the Lady of Acceleration Church ad-ministers punishment in internet forums that are subscribed to by insane dieselhaulics.



How'd I do? There must be a second meaning... . anybody?



E C Jay