Turning Up Fuel Question

[Tristan]

So when we turn up the fuel screw on our injection pumps are we just raising the maximum amount of fuel the pump is able to deliver at full throttle or does it increase the amount of fuel delivered at all throttle positions?
Tristan

 

[jauguston]

Maximum at full throttle.

Jim

 

[Black dawg]

it does increase the amount at all throttle positions

 

[seanpistol]

so obviously your fuel mileage worsens, correct?

 

[Black dawg]

no mileage will not get worse unless you are using the extra power all the time. at cruise speed, lets say 2000rpm the motor can only burn a certain amount of fuel to do a certain amount of work. if you add fuel it will go faster.

 

[Tristan]

Maximum at full throttle.

Jim

it does increase the amount at all throttle positions

So which one is correct?

 

[argve]

techincally both are correct...

here it is in laymen's terms...

Let's say that in order for your truck to cruise at 60 mph you had to push the pedal down half way which would in turn cause the pump to push 100cc of fuel for every pulse of the injectors...

Then you went out and turned your fuel pump up...

So now to do the same 60 mph on the same road under the same conditions you will only have to push the pedal down 1/3rd of the way and you would still only need 100 cc of fuel to be pushed. But if you press the pedal down 1/2 way you would flow 160 cc of fuel and then it would cause you go faster.

Now with a stock pump let's say that it would move 200 cc of fuel at full throttle and after turning up the pump it can move 320 cc of fuel at full throttle.

So as you can see both answers are correct.

Another thing happens let's say your hauling a load up a grade with a stock tuned pump and the tranny wants to hunt between gears but you pull over and crank up the pump then after pulling the same grade with the same load it will stop this.... now why is this you ask - simple my dear Watson... the tranny will choose when to shift by how far you have shoved the pedal down but since you are flowing more fuel for the same pedal deflection you won't be pushing down on it as hard so the tranny "thinks" you are driving easier and not calling for a different gear.

Disclaimer... The numbers quoted in this message are NOT CORRECT VALUES - they are only used to illustrate how the system interacts - again not hard values...

 

[Tristan]

Thanks for clearing it up Travis. When I installed my turbo I only turned my pump up as much as Banks recommended. Now I am wondering if I want to go more. With a load such as a big hill I always have to back out of it to limit my boost. Until I do studs and new head gaskets I am limiting myself to 10 psi. I have seen boost as high as 11 to 13, so I don't really need to increase the max or full throttle fuel output. It is just at normal driving I seem to have to push on the go pedal more than it seems I should.
So if I understand correctly, if I were to turn the fuel up the 1/4 throttle I give it now to get off the line would be reduced to say 1/8th throttle?

 

[Black dawg]

Travis, ive heard stated that these pumps could be built with different fueling curves. do you know if that is true? it sure would be useful to hold off the fuel till up in the rpms a little to limit smoke on a non wastegated set up. what we need is an afc setup like the p-pump. has anyone used the hypermax fuel limiting deal.

 

[argve]

Have heard it but I don't know how to do it. I would almost lay a bet that it has to do with the cam ring and metering valve set up. Because these are the two items that set up the fuel delivery that is dependent or looking at rpms and pedal travel.

You can get a better look at the internals >>> HERE <<<

 

[metrojd]

Turning up the fuel

I was woundering if anyone could help me?
I was going to turn up my pump. ATS says take out 1/4 in screws and open access , remove rubber gasket and turn engine until you 5/32 allen screw is centered in the opening and turn 1/4 turn.
Sounds easy enough, I took off the access plate, removed the gasket and turned the engine and I dont see a hole lot happening.
What is going to happen?
It looks like there is a hole on the back side of the access hole,Is that going to move forward? or in that hole is there the screw?
I dont know if I need to keep turning or I am doing something wrong.
Thanks
John

 

[Black dawg]

i usually remove the plate on the pump gear housing, the plate right below the oil filler on a 7.3 or the oil filler itself on a 6.9. bar the motor over till the dowel pin is 12 oclock. that will put the fuel screw were you need it or very close. make sure your allen wrench engages the screw completely and that the end of it is in good shape the fuel screw turns pretty hard.

 

[Diesel JD]

Can you make the gear jump timing with the pump attached or only if it is taken off? It seems like taking off the gear cover would give more clearance, but is it worth the risk of messing up your timing??

 

[Black dawg]

not the gear cover, the access plate to get to the pump to gear bolts

 

[Diesel JD]

Oh I was being a big dummy, I think you mean the fuel filler neck on a 6.9 then right? Gives access to viewing the dowel pin on the IP gear?