Fuel Screw on 1989 Truck....

[AndrewKing]

HI,



Just wondering but If I turn the fuel screw OUT what would the effects be?... The screw I am talking about is the one under the protective cap close to the engine block not the screw under the AFC cap... . (would the effects be linear decrease in fueling throttle position for throttle position or does it only affect max fueling with no effects along the way.

Thanks

Andrew

 

[MEby]

Dude, dont do that. :-laf I think it would affect fueling over the entire rpm range.

 

[dpuckett]

Yes, it would affect fuelling over the entire RPM range, to the negative in terms of power, and likely, MPGs. Why do you ask?



What is this protective cap you are talking about? I know the AFC housing has one in the middle, and I've had a few trucks with a cap over the high idle screw... ...



Daniel

 

[AndrewKing]

HI,

Thanks for the replies thus far... I am hoping to lower the power on the truck a bit in the hopes of making life easier on the transmission and hopefully get a little more MPGs along the way (less available fuel equals better mileage right?)... . I would not do this on my personal truck but this is a company truck that my helpers will be driving for lawn care and I think the driver is a little heavy footed as it is... . Plus the transmission shudders a little as it sits so maybe lessening the power of the engine will help the transmission make it a few more seasons before a rebuild (I don't think it is slipping now... . Have gotten as high as 20. 3 MPG on the hwy at 62 MPH with the ac on... . In town towing of a landscape trailer nets 14. 3 MPGs with me driving... . be interesting to see what kinds f mileage figures my helpers will post but I will help them all I can mileage wise!

Andrew

 

[AndrewKing]

OOPs the protective cap I am talking about is on the screw closest to the engine block... I believe that is a fuel screw too? ( I already uncovered the HI idle stop screw and have limited overall throttle to approx 50% travel... . I would have simply put a block of wood or bolt under the accel pedal but I think my helpers would have disabled that in short order..... I was a little more devious by telling them that I had a shop install smaller injectors for less power and better MPGs... . (If I told them the truth about the screws I think they would have readjusted without my knowledge)... . Wow the things we do to try to save $$ ;-O

Andrew

 

[TWorline]

Andrew:

I hope for your sake that nobody turns them on to this site!:-laf

 

[MEby]

I think the cap he is reffering to is the collar on the full fuel screw.

 

[AKaiser]

If it's anything like what's on the old Rotary Pump DT466Cs, when you back it out, you get lots of power, and LOTS of SMOKE.

 

[dpuckett]

Back it out and you get NO POWER and probaly NO SMOKE. There are MANY different types of rotary pumps.



Now, back to the fuel screw tampering. I would leave it alone, and cut/ unhook the AFC hose, or tighten the spring way up. If your transmission shudders, it isnt going to get any better, and turning down the pump (and likely, MPGs) isnt going to help. Get the transmission looked at and fixed. Nothing is more aggravating to a hired hand than a employer who wont maintain stuff like he/she should. (Ask the guy with the KW dump truck with horible steering slack, no power, and cracked tiny spot mirrors I drove for almost a week. )



I can almost guarantee you that less fuel available does NOT equal less fuel used. Less pedal applied can equate to less fuel used. Most of the time, more fuel available, but not used, can mean better MPGs. Has to do with atomization and getting the fuel in there at once instead of spread out over several degrees of crank rotation.



DP

 

[AndrewKing]

HI,

Thanks for the info concerning the fuel screw... . The other theory of helping the trans live was that by turning down the fuel less power would be made for any given throttle position therefore it would be easier on the trans... . Not only that but secondly, the greater the throttle position needed for a given speed (due to lower engine power), the further out the Trans TV cable is pulled so the trans should be applying more pressure to the bands thus further aiding trans life... .

Overall the best solution is as you stated have a good trans and a truck tuned for max power / efficiency and a driver that cares about not tearing stuff up and driving for economy..... The first two would be easy enough for me to do or have done... . unfortunately no matter how hard I talk with the help, I believe they will not drive for max economy... . I did think about making them pay for fuel beyond

what MPGs the truck should get if driven for economy.

Andrew



PS - I have heard of a valet switch used to cut the boost signal to the afc housing... . Is there a tech article on how this is done or made?... . Could it be as simple or crude as cutting the metal line and instaling a ball valve or some sort of manual valve inline?... . I can weld if needed.

 

[dpuckett]

Another idea is a fuel economy bonus- if they achieve a certain MPG for the month, they get a bonus of some sort. Like, maybe half the difference (of what thye'd normally use) split among them. Probably not enough incentive, though. It sucks having the only performance vehicle around, then the help gets to drive it. I get into a Powerstroke, and it's "Yawwwnnnnn, when is this thing going to move out of its own way?"



MPGs will vary considerably. You SHOULD see 19-22 empty hwy; 17-20 in town. That's if everything is up to snuff. Loaded, it's hard to say. A lot of stop and go will pull your MPG through the floor, as it takes a lot of fuel to get the load moving, much more than just keeping it going down the highway.



For the AFC, you can install a valet switch, or just loosen the banjo bolt. Cant help ya on the valet idea. PToombs has an elaborate setup under his hood.



Or find new help. :-laf

 

[AKaiser]

I can almost guarantee you that less fuel available does NOT equal less fuel used. Less pedal applied can equate to less fuel used. Most of the time, more fuel available, but not used, can mean better MPGs. Has to do with atomization and getting the fuel in there at once instead of spread out over several degrees of crank rotation.



DP

True. It's like the difference between 4 barrel carbs and 2 barrel carbs. Four bbl carbs usually get better MPGs, as long as you keep your foot out of it. Why? Because the primaries have smaller jets than a std 2 bbl.