Injector pump questions.

[Idually]

Hey there! Just a couple of quick questions. I went to turn te AFC pin on my 1993 W-350 and just take apeek at a few things. Pulled the top of the AFC housing and found the Star Wheel turned all the way in? I mean ALL the way. I would think that my truck would smoke quite a bit more than it does when you get on it. Doesn't smoke too bad at all. Sound like a problem?



Also the little fuel pin down in the AFC bore that rides on the AFC pic seemed to be stuck. I didn't notice this on the '89 when I was "playing" with the AFC, but the pin "pops" out of it's hole when the throttle gets to about 3/4. Went to push it back in and it sort of "popped" back in? Is it spring loaded or should it move freely with the throttle?



I'm also chasing a bit of a power issue also and I just happened to be looking into the AFC, when I noticed these things.



What do you think?



Thanks!

Andrew

 

[TMWeber]

Was hoping that someone would reply, I have the same fuel pin thing happening and I don't know if it's normal... ?

 

[Greenleaf]

Hi guys. I'd be more than happy to help but my answers/explanations are long winded and nobody likes that.





I also have the opinion that the AFC is a worthless piece. Not all pumps have 'em you know.





The star wheel can be @ any location. Don't matter. A tighter spring nets later fuel and a loose spring net quicker fuel per pound boost. If you have a pump that isn't turned up dramatically, then a wheel setting at the bottom isn't going to make smoke.



A tight O ring on that fuel pin will not allow it to "pop". That doesn't mean it's siezed. You have to determine that. There is a method used to do so. The pin is free floating in it's bore. It is operated by forces and thus moves in/out accordingly to the forces acted upon it.



I'll stop now unless you really want an explanation of what moves the pin and how to check for an inop pin.



-S

 

[TMWeber]

I'm all ears... .....



My pump is mildly tweaked- 1/4 turn on fuel screw, starwheel near top, AFC not at full position, actually about 1/2. I get smoke when shifting, light puff if light on accelerator, really good puff if firm. The last two times I took the cover off the AFC, the diaphram/shaft were stuck down, I could not pull it up. I had to press it down a few times then it would pop up. The fuel pin is as decribed above, it pops out when I move the throttle linkage and I have to push it in manually. I was thinking that it is sticking in the out position. That is why I get more smoke than I should be (at least I think I am) and that is what it holding the AFC down. What do you think??

 

[Greenleaf]

I'd seriously doubt that the diaphram return spring would not allow for the control cone to return with a sticky fuel pin, however stranger things have happened. You can push it in manually right? ... ... ... ... ... . and it pops out by working the throttle?... ... ... ... ... ..... That's odd that the cone is stuck down. Something is hanging up. It's supposed to have a light film of heavy grease in there you know.



It's evident that the fuel pin is not stuck. They are loose with age but a fresh O ring will cause quite a bit of drag to the point that the pin will not pop out yet it takes some effort to push back into the pump. They still operate normally with a tight O ring.



The reverse lever (inside of pump) is pushing against the innar end via the governor linkage/spring and the AFC spring and control cone are forcing it back into the pump. If you need further explanation, I'll have to reread the Bosch manual myself to explane it in further detail.

 

[Idually]

Thanks Scott. You answered my question, plus a bit more. I think mine is o. k. I appreciate it. Interesting thing these pumps are. I want experiment a bit more, but not until I get guages. I keep sayin' I'm gonna', but money seems to always be too tight. I have a Digital temp guage(accept J&K thermocouple inputs and is 12vdc. Pretty slick. Just wish I could get some matching ones for the other guages) that is built by on of our vendor, so I really only need the probe and wires for on of the two trucks.



Thanks again, guys!

Andrew

 

[TMWeber]

A light film of heavy grease? I don't see any. I'll try that. Thanks.