Engine/Transmission (1994 - 1998) Fuel control arm adjustment lessons learned

[A-bomb]

I did a search on this before I began the process of adjusting and did not find anything, so I decided to post this for future references.

After looking at the PDR site one of the technical subjects inculded adjusting the fuel control arm. After adjusting as described I was not happy with the results and proceeded to spend 8 hours playing with adjustments until I figured out what was what and what worked best.



My goal was to speed up the fueling at lower rpm, while not creating a whole lot of extra smoke. So, I went to the fuel control arm. The fuel control arm hits the AFC lever and or fuel cam plate. As boost increases the AFC lever moves forward and they fuel control arm moves with it, increasing fuel. The PDR site suggests moving the lever to where it just hits the camp plate. However when you do this the fueling rate is slowed down, due to the fact the AFC lever is controling the fueling as boost rises. So, when you move the lever to where it actually hits the cam plate it forces the fuel control rack not to move forward as much, reducing the fueling rate as the AVF moves forward. So I moved the fuel control arm the other direction and got more favorable results. However, be carefull not to move the set screw too far out or it will fall off into the governor. I had to modify a few tools to adjust this while in the truck. The concept is simple, but the set screw is very difficult to get to with the pump on the truck. Also, make sure you take the fuel solenoid off and make adjustment with the fuel lever in the run position. Here are some photos.

 

[Howard Durand]

Hope others chime in here with their input. I have a #10 plate in mine. I adjusted the arm to touch the plate just above the lower nose which required backing out the screw to near the point of falling out. (In fact, it did fall out).

The low end acceleration is good with little smoke but it stops fueling at around 2300 rpm, long before full throttle.

I am thinking that moving the plate forward would help. It is already 0. 030" forward from stock setting.

 

[A-bomb]

The further you turn the srew in the more it decreases the fueling. The AFC lever controls the fueling to a point as the fuel control lever rides against it. Moving your fuel plate forward may or may not help as the distance of the AFC fuel contorl arm controls most of the fueling and when it is fully pushed forward there it is really not that much distance for the fuel control arm to travel. I understand why some people dont even use a plate.



How and the heck did you get the set screw out of the govenor housing?

 

[Howard Durand]

I was able to retrieve it with a magnet on a flexible extension.

 

[A-bomb]

One final note,



After putting about 200 miles on the truck since the adjustments I have a noticeable improvement in the smoothness of acceleration. Before the adjustment I had a lull in the power band from 1400 to 2100 rpm, now it is a steady increase until about 1900rpm, when the boost realy kicks in and then it is like turning on the after burners. Also there is very minimal smoking between gear shifts as the boost catches up with the change in rpms ( I have a manual). This would probably be less noticeable on a auto. I am currently using the DDIII injectors instead of my 370's. I found the 370's to be a little too smokey. As you may have guessed I do not like smoke, as smoke is unburned fuel, and unburned fuel is a waste of money. My timing is set at 15. 5 degrees and I have the 3K govenor springs. The rpm's peak at 3200 on my tach, so the springs could be a little loose or my tach could be off calibration. I do not think I could do anything else to make it run better with the current set up. The next level would involve a great deal more money - and I am currently satisfied with the performance. Certainly better than stock.



I am checking the fuel mileage and so far it looks like I may have lost a little, but that would be expected as the engine is getting feed more fuel. As my engine says : "FEED ME SEEMORE!" (Little Shop of Horrors - movie quote)

 

[Cooker]

Sometimes, depending on the design of the plate, the fuel control arm can get caught under the nose of the plate. This is why PDR recommends adjusting the FCA to hitting the nose of the plate.

 

[Howard Durand]

A-bomb,



What plate are you using? The #10 plate that I have is shaped like a lazy V. The control arm is adjusted to touch the nose of the lower arm of the v. If it was adjusted any lower it would go under the plate. A little bit lower than that and the screw falls out.

I am assuming that as the arm moves forward it rises, folowing the v. When it hits the forward point of the horizontal v it then has to move back if it is to rise any further.

Obviously there is vertical travel of the arm as well as horizontal.

I further assume that the vertical movement has an effect on fueling as well as horizontal movement.



The way mine is set, when towing the trailer, it backs off on the fuel somewhere around 2000 rpm and peters out at about 2200 to 2300. There is a considerable amount of throttle left but no response.

The plate is now 0. 030" forward of stock position and I am going to try moving it further if not fully forward and see how that works.

Bear in mind your pump is designed for a lot more hp than my little 160. I hear a lot of praise for the #10 plate and I like the way it performs on the low end but would like to get it to run up to 3000 or better.

 

[A-bomb]

I think I am using a #10 plate also, as it is shaped like a v. However I decided to adjust the fuel control arm as far out as I could without the screw falling out. This adjustment is just before the tip of the AFC control arm. The fuel control arm has to rise as rpm increases to follow the profile on the fuel plate. However I have a set of AFC springs in my housing that are less tension than the stock, so it will take less boost to raise the fuel - up to the point where the AFC control arm is moved forward enough for the cam plate to control the fueling. However, after carfully measuring the travel on the AFC arm and distance the cam plate offers, there is very little tolerance or room for the AFC lever to let the fuel control arm to move into the profile of the fuel cam. So, I put the fuel plate just beyond the measured maximum travel of the AFC arm, figuring that if the AFC travel ran out there is no more tavel left for the fuel control arm to go forward, therfore only following the cam profile as rpm rises and to the point where boost allows the AFC arm to go forward allowing more fueling.



With your control arm adjusted to where it just touches the fuel plate, you are limiting your fuel. I would move the fuel plate more forward to allow the AFC arm complete control for it's limits of travel and move the fuel control arm back, by turning screw clockwise, to give more fueling as the rpms rise. The fueling is controled by engine rpm, then boost. So, if you run out of travel on the fuel control arm it will not fuel more irregardless of rpm or boost, it will just follow the profile of the fuel cam as rpms rise, then as boost increases the AFC arm will travel forward allowing more fueling. In your case the AFC lever is moving forward with boost, but the distance the fuel control arm is traveling is limited and may not have enough travel in it to follow the cam plate as boost and rpm go up.



The bottom line is move your fuel plate almost all the way forward and adust your fuel control arm to where it just touchs the AFC control arm. Also set the preload on the AFC spring as low as possible to allow faster fueling as your boost increases. In your case this may make a lot of smoke, as we do not have the same components. In my case this set up gave me just a little smoke between gear shifts, but very linear accleration until about 1800 rpm, where the HX40 really starts to produce, there by greatly increasing the volume and pressure of air, and of cours AFC responding accordingly. Like I said earlier - afterburners.



I hope I made sense.

 

[Howard Durand]

It is beginning to make sense to me.



From what you are saying, we want the AFC to move ahead of the Fuel Control Arm as far as it will go with the cam plate situated to intercept the FCA at that point. The FCA will then follow the contour of the plate upward to complete the fueling process.

 

[Andy Redmond]

Good points are made, the reason most of the time to adjust is when using a Number 8,6 or 5 plate, which have a good knob on the end. Often the truck will start to go then boom the bomb goes off. The number 10 and four plate have such a shallow heel (where the lever hits) it is not usually necessary to be adjusted. You can get some more low end by afc position, richness and pre-boost fueling, you can also adjust the eccentric on the afc to lower or raise how far it hangs down in the pump (lever contact). Richness on this one is pushing the eccentric towards the intake/lean is away. Moderation is key on all adjustments. A-bomb noted some cause/effect of changes.



Search for a post that Jim Fulmer chimed in on (within last six mos). He extoled the virtues of moving the lever with a number 10 or 4 profile and how it affects power band.



Good luck

Andy

 

[A-bomb]

Howard,



That is exactly what I was trying to say. I guess I did make a little sense. I do not have experience with the other fuel plates, so I could see where the adjust of the fuel control arm in relation to the other cam plate profiles could be usefull. Good luck with your adjustments.

 

[Howard Durand]

Would a set of AFC springs from Piers, or whoever, improve my setup?



Another adjustment that has been recommended but not really talked about is movement of the AFC housing. TST instructions for the #5 plate call for it to be moved fully forward. It looks to me like this may be a way of fine tuning the relationship between where the AFC lever stops and location of the plate.

Right now, mine is set at the factory location.

I am guessing that my fueling stops before the pump reaches full throttle because of the combination of AFC position and plate location that I have mine set at.

The only things I have adjusted so far are the plate location and the fuel control arm.



It seems to me that it would make sense to remove the AFC housing and make a mark on it, locating the end of travel for the AFC lever then transfer that mark to the governor housing. That way I could get a better idea where the plate should be located.

 

[RWood]

I just took off the AFC housing and it doesn't appear that I have a fuel control lever or arm, the peice that pushes on the AFC lever. Is this a bad thing? The truck runs fine.

 

[A-bomb]

Howard,



Your last post makes sense to me. I think it would be a good idea to fiddle with the position of the AFC housing itself, as this would add more travel to the fuel contorl arm. I think the piers springs are a good investment, as they allow you to better tune the amount of presure from the boost to control the fuel. Your final adjustments will be a balance between smoke and power. If you move the AFC to forward you may get a lot of smoke ahead of the boost. My final adjustments ended up leaving the AFC housing just a little further forward than stock.

 

[A-bomb]

Rwood,

You have to remove the fuel cam to see the control arm. It is in there.

 

[RWood]

I have removed the AFC housing and it should be on the cab side of the fuel plate right? If so I can't see it. Also when I move the throtle the only movement is the rod below and to the right. when that ro d moves toward the front of the engine should it move backwards at the top of the throttle range?

Thanks,

Ramsey

 

[Got Smoke?]

Guys you don't have to remove your fuel/cam/torque plate to see the Gov. arm.



I just checked mine today to see where its riding on my current "custom" plate.



What you need to do is, remove the AFC housing, turn you ignition key to the "on" position, then pull the fuel shutoffsolenoid arm to the UP position(VERY IMPORTANT, if its not in the UP position the arm will barely contact the plate and snap back out of sight).



Now reach down to the throttle linkage and slow start to advance it. You should see your Gov. arm come into view, where its contacting the plate, and if its going under or riding up the plate.

 

[RWood]

yeah I found it. It was stuffed down in the back of the housing. With the fuel shut-off solenoid in the up positions the governer lever still can't be seen, but when you work the throttle linkage it comes into view and hits the cam plate.