Removing AFC spring?

[bgilbert]

Whats with removing the AFC diaphragm spring? A neighbor of mine has bought a 93 W250 CTD, and of course with no guages, never heard of TDR, has done major injection pump adjustments. Governor turned up, full fuel wide open back 1/4 turn woo hoo, and his AFC diaphragm spring removed. Boy does it smoke. I wouldnt let him touch my virgin pump.

So anyways, I was bored waiting on my pods to show up, thought I'd check inside my pump see if my spring was still there. It was, so what the heck, removed it to see what happens. Only thing I really noticed was the low end smoke covering my tailgate and vehicles directly behind me. So the ? is, does this hurt anything, the truck, pump etc? TIA, Bill

 

[phillips5]

I have had my afc screw botomed out for 400000 miles and nothing has hapened yet. Except for I can't see behind me when I nail it.

 

[dpuckett]

wise move, bgilbert, regarding the neighbor touching your pump......

The AFC (Air Fuel Control) is a smoke reduction device. It cuts no boost fuelling by about half, then allows more fuel as boost builds. Naturally, this being a mechanical engine, it is adjustable. The only thing removing it does is allow full fuel off idle, increasing smoke, EGTs, etc. It can also allow the guide pin that rides against the AFC tapered cone to pop all the way out, allowing fuel to fill the well. Sounds like your neighbor isnt the sharpest knife in the drawer. Ignorance must be bliss.



Daniel

 

[BushWakr - RIP]

You really shouldn't run without an AFC spring. All the reasons above apply... . extreme smoke, excessive oil contamination, problems with the law, including imparing the vision of other drivers, terrible mileage, serious soot'ing of all the internals including the injectors, valves and so forth... besides it is absolutely not needed for performance.

You can make a 1st gen truck haul apples as good or even better with a fraction of the smoke. . honest. . ok, so smoke is kinda fun sometimes...



But, hey, that's just my opinion and what do I know... .



PB.

 

[hdm48]

Bob, you need to go over there and smack that guy with your stick.

If I'm not mistaken, this issue was covered a LLLOOOONNNNGGGG time ago and got the same answer.

LEAVE THE SPRING THERE!!!

 

[Greenleaf]

I removed mine one time for a trip through the neighborhood. I put it back in for fear of engine damage such as clogged injectors and cylinder wash down/perhaps making a mess in the combustion chambers.



However, older engines use no such device so am inclined to think it may not pose much of a problem after all.



I will conclude with the fact that the older engines did not last as long as these "newer" engines because they were often times over-fuled and washed down cylinder walls and lube oil contamination.



-S

 

[bgilbert]

Thanks guys, I'm putting the spring back. Yes I like smoke, but not at the expense of the engine internals, sooting the oil etc. Thats what I was waiting for, was the effects of what it would do to the engine, and to hear Bob's opinion on this. Thanks again guys. Bill

 

[JLEONARD]

The donor truck my son owns has the spring removed... yes, she sure does smoke... even at a high idle!

Luckily we found the spring... . the ashtray made a good storage bin. Spring goes back in before we run it in the "new " vehicle.

But ... perhaps a weaker spring?

Naw... coulnd't do that!

Jay

 

[dpuckett]

Jay, I have heard about guys removing the starwheel to get as little pretension on the spring as possible, though why is beyond me. Mine is 6 turns up from the bottom, and it smokes more than I want. The axle has a fine layer of soot from 1000mi of a short exhaust- too cheap to buy the parts to finish it out... .



Daniel

 

[Greenleaf]

Sans Starwheel.

Will need to reinstall when I modify the pump linkages inside the gov housing to control the smoke..... or so I am inclined to think.



I did not notice any difference between the wheel at lowest point and removed altogether. Simply experimentation.



-S