I turned my full power screw in till the lock collar hit which was at least 3/4 of a turn and noticed very little, if any, difference in performance. One of the pages with instructions to turn up the pump says this:

"According to the TST webpage, a few engines can't be turned up with these adjustments and they must have larger injectors installed to increase engine power."

How common is this? Are there certain years that are more prone to this problem than others? Should 3/4 of a turn on the full power screw shown some noticable improvement?

 

Have you checked the throttle linkage to make sure you are getting full throttle at the pump?


Den

 

Hi Den,

Yes. That was one of the very first things I did after buying the truck and doing some research here. I also backed the high idle screw out to give that little extra bit of travel in the linkage.

I did notice a nice improvement in power and throttle response after adding the BHAF and turning the smoke screw in 2 turns. I thought that 3/4 of a turn on the full power screw was really going to make a big difference, but I can't tell a difference at all. Also, there is no additional smoke with the full power screw in 3/4 of a turn.

 

Did your idle go up any at all with the 3/4 turn? If your pump is a bit tired, it might not be as responsive to tuning as a fresher one, but in any event, I think you're going to have to lose that lock collar to get any tangible results. As a rule, the injectors on factory intercooled trucks don't flow as well as the older stockers, so you'll likely be in the market for new sticks before long anyway...but try removing the lock collar first since that's a free mod!

 

My idle did seem to go up a little bit and I lowered it using the idle adjust screw. Any tips on removing that collar without having to take the screw all the way out?

 

Nope. Just pull it out, it's much easier that way. Won't hurt anything, you'll just spill a few drops of fuel.

 

Yep, do just as Dave says. I pulled my full fuel screw out without anybody saying I could about 10 years ago and carefull pulled the collar off. Played with it until I could hit almost 25lbs of boost and advanced the timing to 1.7mm. Your 93 should pull this boost easily unless something is amiss with your pump. You'll know your progressing when your idle starts climbing up as you turn the screw inwards.

 

Open the AFC and pull out the eccentric pin (sp?). Function the throttle linkage to make the fuel pin pop out of it's bore, makeing sure you remember the original position. The pin rides the cone you took out. Functioning the linkage all the way will cause the pin to pop back in place. This is an open-air area, so sometimes the fuel pin can get corroded and not come all the way out allowing fuel delivery and may need to be cleaned up. Don't do this with the engine running. When you put the cone back in, turn it 90 deg so the steepest angle is towards the front of the truck so the fuel pin rides here. You'll probabl, but not necessarily see the factory position wore on the cone.

 

Collar is in the garbage and now I notice a difference.

I tried getting into the AFC and it has 1 flathead screw that I can't get undone without stipping the head. The other 3 are allen head bolts and were easy to loosen. Why would they use a flathead screw instead of a bolt or allen head fastner?

Anyway, any ideas on how to get that 1 flathead screw out? I've tried using a ratchet and flathead bit but it still slips out.

 

Get a bigger screwdriver bit.

 

You might try soakig the screw with PB Blaster for a couple of hours, several applications. Then use an impact screwdriver, the type that you pound on the end of the handle to make it turn. If you don't have an impact screwdriver you can tap on the end of the screwdriver handle as hard as is safe while turning and it will come out. Works on steel bolts that are REALLY stuck in aluminum housings on motorcycles. The hand impact screwdriver is best and they're fairly cheap at the parts house. It will get a lot of use over the years....

JimmieD

 

After I got mine apart the second time I drilled them all out and put in stainless steel 1/4-20 socket head cap screws with nylock nuts in their place. It makes life a little easier for me.

 

PB Blaster rules!

on my 98, I had a flathead screw in my AFC cover that wasn't wanting to cooperate, so I used a small chisel on the edge of the screw to get it started. worked great, promptly threw the screw away

 

Small vice grips worked for me. Replace them with allen-head screws once you get them out--you'll be glad you did next time you go to get in there. I told 'ya that lock collar had to go--fun now, isn't it?

 

Sounds like somebody might have already been in there. Might have stripped the oem screw and put an oversized screw in with thread lock?