xtremexj

OK, here's the deal. I installed my 3200 spring yesterday and tried to turn up the power screw after removing the collar. I could only turn the power screw in far enough to leave about 6 threads or 1/4" showing out from the jam nut. I only had to turn the low idle screw back a couple turns - it still has about 1/2" of threads forward of the front threaded boss. Does this seem normal? This pump was rebuilt by the PO and I would have thought that I could get the power screw in further. Is it possible that I didn't put something in right when I reassembled the AFC?

G1625S

Sometimes the threads need to be chased on the fuel screw to get it to go all the way in. My buddys truck is that way--I gently took the collar off and the threads looked fine, but we couldn't get much more than when the lock collar was on. once the threads are cleaned up, ust remember to make small adjustments to avoid a runaway

xtremexj

With the jam nut backed off a few threads, I still can't get it to turn in. The screw feels very tight and this is no where near the collar marks going into the pump. I don't want to bend anything by trying to turn it more.

G1625S

yeah, that's the same way my buddys was...we haven't gone any further with it since he's an OTR driver and is not around much. From a safety stan point, I'd try removing the AFC housing again and running the screw in and out...you'll avoid any damage to pump internals this way and you'll be able to see what's going on.

xtremexj

I don't know if this makes it any better, but when I put the AFC cover back on, rather than use Den's wire trick to pull the lever forward while installing the cover, I backed the power screw completely out so it wouldn't interfere with anything. Maybe I've got one of those pumps that just won't go any further.

jrussell

Hi Shane,

I was just going to answer your PM, but figured I would post here instead. Sorry it took me so long. I've had internet access problems all morning.

Mine shows 7-7.5 threads after the jam nut (when tight). I estimate my screw is about 3-4 turns in from stock, so it sounds like your's is pretty far in if only 4-6 thread are showing.

I tried the wire trick for about 30 minutes and then just backed the screw out to get the cover on. If you back it out all the way I don't think anything can really go wrong when you put the cover back on. If you haven't already you might want to check your fuel pin and make sure it's cycling properly. When I first turned my fuel screw in there was not much of a power difference because my pin was still sticking at the time.

Later,

Justin

EDIT TO ADD: Turning the low idle screw a couple turns should make a pretty big difference in the idle, unless the stop isn't actually contacting the screw anymore. The stop on mine doesn't hit the low idle screw. It's stopped by the throttle linkage instead and I'm pretty much out of adjustment there.

xtremexj

I installed my Bully Dog pin while I was in there and turned the star wheel down 1/2 turn. It is definitely moving as I get a nice puff of black smoke when I stab the throttle. How much of your low idle screw is sticking out between the stop on the lever and the forward threaded boss?

Bill Tomlinson

Your truck is a '93. It comes with little teeny injectors. You can't really turn things up all that much without an injector change. My old non-IC'd truck has big nasty injectors and will pump in lots of fuel. Yours has a stronger head because of the smaller injectors. Just a thought. The PO may have had the fuel turned right up but it may not produce the results it does on the older trucks.

gman07

Bill is right, the IC trucks don't turn up much without injectors. My fuel screw is also bottomed out (the o-ring on the screw is up against the threads in the pump). I have toyed with the idea of making a longer screw, but I think injectors are probably an easier alternative. With the stock turbo (H1C/18) and BHAF I was only hitting 25psi and 1100* with the pump all the way up.

xtremexj

Tach is working now and low idle is set to 800 in park and about 750 in gear with the brake on. I set high idle at 3200 - I am assuming that that is were you would want it with the 3200 spring, right? Let me know if I should change this.

G1625S

There are a couple different theories on the high idle subject...The 'safe' way to go is this: Completely remove the high idle screw. Cycle the throttle linkage by hand untill you feel the linkage hit a 'stop' inside the pump...in other words, the throttle won't twist any further. Now, thread the high idle screw back in far enough so that it stops throttle travel just BEFORE the previously found internal stopping point. The theory is that when you wack the throttle wide open from a stop (I know, who does that? ) you won't damage any internal pump parts since the high idle screw takes the hit. The other method is to simply remove the high idle screw. Those who do claim no internal damage can be done...and some of those folks have pretty wicked rides. Of course, for insurance reasons, I recommend you have a Bosch certified shop rebuild your pump to stock specs and just leave it alone so noone ever gets hurt and you completely alleviate the possibility of having any (gasp!) fun I've been using the first method with good results, though lately I've been harder on my truck and have noticed boost dropping off before 3k...not sure if it's just running out of fuel (stock-style lift pump) or if I could use some more throttle travel. In any event, a STOCK gov spring will free-rev in neutral to 3k and over, so setting the high idle stop to 3200 is, IMO, not taking full advantage of the 366 spring...run that high idle out a bit more I can rev to over 3500 in neutral...with more pedal to go, but I'm afraid to float the valves. Fre-rev and full fuel are different animals.
greg

xtremexj

Thanks Greg. I'll have to wait to take it for a good test drive and I'll determine if I can bring it up a little more. I'm waiting for my Stage IV/16cm and 4" exhaust to show up so I'll probably wait until that's all in.

xtremexj

Another reason I set the high idle for 3200rpm was because someone posted a pic of a dyno sheet from the pre and post 3200 spring installation, and peak power was made at 2500. I figured using that as a guideline would give me a little more to play with.

apwatson50

I wouldn't do it that way. First your no load high idle is going to be very different than you loaded rpms. I don't know how high I can get my idle with no load don't really want to know. I'm more worried about how many rpms I can turn with a load and to do that you want as much throttle travel as possible. I believe that setting you high idle screw that way will severly limit your throttle travel. I did the turn the shaft as far as possible with the high idle screw out then turn it in untill it just limits the travel.

With a load in the mountains I can turn just over 3000rpms before I need to shift and a few more rpm's wouldn't hurt for the 3rd to 4th shift.

wannadiesel

Good posts from G1625S and apwatson50.