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Discussion Starter #1 (Edited)
DISCLAMER: Like all good things, what you do with this information is your own business, and your own problem. Nobody at this site, or any other site is responsible for your use of this information.

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Low manifold pressure (boost) fuel delivery adjustment.
A.K.A. Smoke Screw Adjustment

NOTE: this will increase the exhaust temperature by about 75 degrees F on long grades.


This adjustment is fairly simple and will help considerably around town at low engine speeds and low boost conditions.

There is a small cap in the center of the 'fuel-control device' atop the pump (the 'appendage' that is plumbed to the intake manifold and restricts the amount of fuel injected until the manifold pressure is above atmospheric).

This cap can be readily removed with two small screwdrivers and a gentle rocking motion. Beneath the cap is a torx T-25 screw and a lock nut that holds it. The locknut is 13 mm and has a 'break-away torque' of around 100 in-lbs. Turn the T-25 screw 2 turns clockwise and tighten the locknut to 125 in-lbs. Clean the plug with CRC Brake cleaner and seal it with LocTite pipe thread sealant with teflon. Externally, it will appear stock.


- For additional fuel (and smoke) the screw may be turned farther (CW).
- Back it off (CCW) to reduce smoke.


Full load fuel delivery rate adjustment.

This adjustment will TURN UP THE POWER and smoke.
NOTE: this will raise the EGT very quickly at full throttle:

The main adjustment (effects are similar to swapping the torque plate on the P7100 pumps) is found under the AFC diaphragm that is held on with a 4-screw cover. This one.



MARK THE POSITION OF THE DIAPHRAGM, then remove the diaphragm -- there is a stamped tick mark on it, so use a magic marker or scribe to note the position of the diaphragm vs. housing.


Remove the diaphragm and shaft, and note the shaft is both tapered and on an eccentric.
I'm only allowed 5 pictures per post, so please click here for a picture of the eccentric/diaphragm assembly


Usually, rotating the shaft 120 degrees clockwise will cause the wear to go to the richest (smallest diameter, effectively) part of the shaft. You may want to start at 90 degrees and then go farther if that does not produce the power you want. The farther you go, the higher and faster EGT will climb. The fuel stop part rubs up and down along this shaft, and note the way to install the shaft that allows maximum travel of the fuel stop part that hits this shaft and is perpendicular to it.

Just pay attention and mark stuff so you can put it back the way it was, and you should be able to figure it out just fine. After adjusting the diaphragm eccentric, the low boost fuel rate may need to be adjusted slightly to reduce low speed smoke. (see the first adjustment, the one under the cap)

Caution: The banjo bolt that holds that air line onto the diaphragm case is very VERY fragile. No need to reef the sucker down. Just snug it up.

AFC Star Wheel Adjustment



Fuel delivery pin is circled in RED. Starwheel is the toothed wheel in the center of the image. The retaining lock is on the right hand side of the starwheel. It is spring loaded and meshes into the teeth on the starwheel.

Under the AFC diaphragm and spring is a star wheel adjustment which sets the spring tension on the fuel load delivery rate diaphragm. If your star wheel (under the AFC spring) is set too high, the delivery rate pin won't move downward as it should with increasing boost levels.

-Turning the star wheel up (counterclockwise) increases the spring pressure, and slows the delivery rate.

I'd suggest turning the star wheel down (clockwise) in 1/4 turn increments until you smoke, then back off (counterclockwise) till smoke is gone to your satisfaction, or smoke on under power, a black haze, not a black soot cloud.

The retaining lock spring doesn't have to be removed, the star wheel will rotate with a small screwdriver gently placed and pried between the wheel and the lock spring. Note the location of the wheel, mark it, and count any turns for reference. Mark this adjustment and direction of turn down in your notebook.

Remember:
Star wheel down (clockwise) = less spring resistance = increased fuel delivery rate (more fuel)



Full Power Adjustment

On the rear of the pump, partially concealed by the fuel lines, and under a cone shaped plastic cap is an other adjustment screw. Remove the plastic cap, remove the metal collar tack-welded to the screw, loosen the jam-nut, and turn the power adjustment screw clockwise about 1 to 2 turns. Write this number down in your notebook.

After turning the Full Power Adjustment, you may need to re-adjust the Smoke Adjustment Screw to reduce low speed smoke, and the idle screw or throttle linkage to correct the idle speed.

Tip: The easiest way to remove the collar is to back the whole unit out of the pump, put it in a vise and remove it (the collar). Be careful not to turn the screw in the lock nut as you are doing this or you will lose the "known" setting of the pump. After removing the collar simply reinstall the unit and adjust accordingly.

I hope this helps. It helped me!
 

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Good info, thanks.

It's a good idea to have the air cleaner removed and a stout 2" X 6" handy when adjusting full power screw or playing with pump settings. In many cases, even most, a fella doesn't know what adjustments have been done in the past. If the pump has already been adjusted up then turning up the screws can cause a runaway and a scattered engine! The 2" X 6" is to slap over the exposed intake to force the engine to stall in event of runaway.

In addition it seems that some engines are more prone to runaway than others. One guy can get 3-4+ turns out of the power screw and no problem, another gets a runaway at 2 or so. Always best to have that 2" X 6" available when fiddling with the pump settings. Trying to use a hand over intake to stop runaway can easily result in a mangled hand and arm as it's sucked into turbo. Screws up the turbo too.....
 

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Discussion Starter #3
JimmieD, you're the man. Forgot about that part, it was covered in the original thread about this, which is where I originally was going to post it. When I decided to start a fresh thread, I forgot all of that awesome info.

-Scotty
 

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Just be sure and pull the pin out first and check to see where it is. Some are already in the more aggressive setting and turning the diaphram will result in power lost instead of gained. I was about to do this write-up, you spared me the trouble, good job.
 

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Great write-up, thanks for the info and the temptation.
 

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Good job!

And this might belong here:

Before doing any of this, INSTALL A PYROMETER!!
 

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Discussion Starter #8
Which one to do first... THAT is the question....
 

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Which one to do first... THAT is the question....
Excellent question, which do y'all suggest?

Perhaps I will install my 12CM turbo and govenor spring first and see what that does, after that which adjustment do you suggest I play with first?

BTW, I have a pyrometer, third most important gauge to the oil pressure and water temp. :)
 

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Howdy all, I now have the turbo and governor spring in! Wow, that woke things up quite a bit.

Now, which adjustment to play with first? I want to keep things dependable and fuel mileage decent. Perhaps an adjustment that kicks in at the higher RPM ranges so I can be selective. :confused: :D

Thanks,
John
 

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I would turn the fuel screw (full power adjustment) in 2-3 turns and leave the rest alone. Blip the throttle a few times as you get close to 2 turns and more, you can tell if your getting close to run away by how the pump returns to idle speed or not... hanging at a higher than normal rpm, slow return to normal rpm etc. I have not had it happen but run away is possible, you should take the intake tube off the turbo and have a board ready to choke off the air in case the injection pump goes WOT and cannot return to idle.
 

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Hello,
I'm getting ready to do this on my CPL 858, which now has a HY35W and the 366 spring. What's the consensus on the order on which these changes should be made, or how they work together (for instance, the full power screw and fuel pin)? My concern is that if I do all, it introduces too many variables.
Any first hand experience would be appreciated.
Thanks,
Mikel
 

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Okay, so this is an ancient thread at this point, but still relevant.

I understand that one way to stop the engine if it is starting to run away is to use a board over the intake, but wouldn't the manual shut-off on the fuel pump do the trick since the run away is related to the fuel pump adjustment? Now if the engine is running away because it has started to use its oil as a fuel source, then most certainly, you need to stop the flow of air into the engine.
 

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It will not "do the trick". Under runaway too much fuel is flowing at pressure too high. The manual shut off cannot slow the fuel down enough where the fuel is not at pop-off pressure for the injectors. Some one correct me if that is not correct but thats the way I understand it. Trust me, I went through this less than a month ago and I pulled and pulled, no dice. I had to use a board over the intake to stop it. Bye-bye turbo seals.
I believe the best and safest way to so this is with the motor running. Back out the screw slowly and as soon as the rpm's start to hang, you need to back off. I went back 3/4 turn from there.

Dave
 

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Okay, so this is an ancient thread at this point, but still relevant.

I understand that one way to stop the engine if it is starting to run away is to use a board over the intake, but wouldn't the manual shut-off on the fuel pump do the trick since the run away is related to the fuel pump adjustment? Now if the engine is running away because it has started to use its oil as a fuel source, then most certainly, you need to stop the flow of air into the engine.
Very nice build thread BTW. Impressive fabrication skills.
 

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Turning the star wheel up (counterclockwise) increases the spring pressure, and slows the delivery rate
I have too much black smoke while under low boost cruising or when spooling under WOT so should i turn the star wheel counterclockwise?
 

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I have too much black smoke while under low boost cruising or when spooling under WOT so should i turn the star wheel counterclockwise?
i turn the starwheel about 180 degress CCW and it seems to help.
 
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