OK...I'm excited... 
I was driving into town this afternoon pondering the remaining difficulties I'm having with the truck. I decided to make a mental comparison of the difficulties and things that I touched or changed during the repairs.
It went something like this.....(fade to dream sequence)...
Remaining problems:
1. Heavy white fuel smoke at start up and some white fuel smoke when throttle is opened.
2. Idle is too fast (est.1000-1200rpm) even with screw backed all the way out. The only was to reduce idle is to back fuel control screw out until all power is gone (too lean).
Things I touched:
1. Injectors...* I am working with the assumption now that 155bar is correct *. Inectors were changed.
2. Glow plugs changed.
Ok.........wait a minute! In order to reach the bottom two pipes on the face of the rotary pump for removal of the injectors, I decided to remove the throttle control plate that sits on top of the pump, and is connected via linkage to the intake manifold butterfly and throttle cable. That throttle plate fits on the pump's throttle post like an indexed gear or cog...it's possible to put it on in more than one position.
What if I put that plate back on in the "closed position", when in fact the pump shaft was actually open, or rotated somewhat? :whoops: What would this do? Well, I thought, it would certainly account for the fast idle, as now even with the idle screw backed all the way out, the shaft would still be rotated too far, hence more fuel/faster idle. Also....(and here is where it gets VERY interesting)...wouldn't putting the plate back on when the post was advanced too far also throw out the relationship between the pump and the intake butterfly valve??? I mean, the linkage is set to balance fuel volume (pump) and air volume (butterfly)??? Throw this relationship off, and suddenly you have too much fuel and not enough air at all throttle settings. For example, if the fuel control post is 15% open when the butterfly valve is closed, then you would expect smoke at idle. Also, that same problem would mean that at any throttle setting, you're getting 115% of the proper amount of fuel for that setting.
Luckily, the test was not hard. The throttle plate is made of two plates actually, and the two plates have an adjustment screw in a slot that allows you to change the relationship between the linkage (aka butterfly) and the fuel pump. I backed off the screw, and moved it along the slot (in other words, reducing the fuel vlume without moving the butterfly valve)...guess what happened?
The idle dropped to near stumble...so I used the idle screw to increase it to perfection...what else?...the white smoke went away!!! regardless of where the fuel control screw is now, I have no white smoke!! I haven't tried it with a cold engine yet, but this is a very encouraging discovery.
I was driving into town this afternoon pondering the remaining difficulties I'm having with the truck. I decided to make a mental comparison of the difficulties and things that I touched or changed during the repairs.
It went something like this.....(fade to dream sequence)...
Remaining problems:
1. Heavy white fuel smoke at start up and some white fuel smoke when throttle is opened.
2. Idle is too fast (est.1000-1200rpm) even with screw backed all the way out. The only was to reduce idle is to back fuel control screw out until all power is gone (too lean).
Things I touched:
1. Injectors...* I am working with the assumption now that 155bar is correct *. Inectors were changed.
2. Glow plugs changed.
Ok.........wait a minute! In order to reach the bottom two pipes on the face of the rotary pump for removal of the injectors, I decided to remove the throttle control plate that sits on top of the pump, and is connected via linkage to the intake manifold butterfly and throttle cable. That throttle plate fits on the pump's throttle post like an indexed gear or cog...it's possible to put it on in more than one position.
What if I put that plate back on in the "closed position", when in fact the pump shaft was actually open, or rotated somewhat? :whoops: What would this do? Well, I thought, it would certainly account for the fast idle, as now even with the idle screw backed all the way out, the shaft would still be rotated too far, hence more fuel/faster idle. Also....(and here is where it gets VERY interesting)...wouldn't putting the plate back on when the post was advanced too far also throw out the relationship between the pump and the intake butterfly valve??? I mean, the linkage is set to balance fuel volume (pump) and air volume (butterfly)??? Throw this relationship off, and suddenly you have too much fuel and not enough air at all throttle settings. For example, if the fuel control post is 15% open when the butterfly valve is closed, then you would expect smoke at idle. Also, that same problem would mean that at any throttle setting, you're getting 115% of the proper amount of fuel for that setting.
Luckily, the test was not hard. The throttle plate is made of two plates actually, and the two plates have an adjustment screw in a slot that allows you to change the relationship between the linkage (aka butterfly) and the fuel pump. I backed off the screw, and moved it along the slot (in other words, reducing the fuel vlume without moving the butterfly valve)...guess what happened?
The idle dropped to near stumble...so I used the idle screw to increase it to perfection...what else?...the white smoke went away!!! regardless of where the fuel control screw is now, I have no white smoke!! I haven't tried it with a cold engine yet, but this is a very encouraging discovery.
