AFC Diaphram Adjustment

[Midnite]

I'm a little confused by the instructions posted on Dave Fritz's website about what to consider the 12:00 position for the AFC diaphram.



One paragraph mentions 12:00 being where the stamped tick mark is pointing toward the valve cover, and the other paragraph mentions it as pointing toward the front of the engine.



I haven't taken it off yet, but it seems to be pointing toward the valve cover. Would that be considered 12:00, or 3:00?



Thanks,

Mike

 

[Gary - K7GLD]

Not sure which instruction you are referring to, but unless your diaphram ha ALREADY been previously adjusted, you SHOULD be able to just apply the suggested NEW adjustment to whatever's already there. I used the 1/4 turn on both the diaphram and star wheel on mine, and it seems to provide exactly the difference I wanted. You're not really likely to hurt anything, and if you are careful to mark current settings, it's quite easy to return to former settings...

 

[Midnite]

Well, at http://www.dodgeram.org/tech/dsl/more_power/Power_ve.htm under the main heading "Full load fuel delivery rate adjustment", in the paragraph "Clarification of how the full load diaphragm eccentric works" is the following:



"... base line for the diaphragm position is 12:00 as you look at the pump. In other words, the tick mark is toward the valve cover, for the normal setting. "



On the other hand, in the next paragraph, labelled "Another TDR Forum explanation" is the following:



"... with 12 o'clock being the engine's front... "



What you say makes perfect sense though, Gary--I guess I'll just turn it 90 degrees clockwise and see how it works.



Thanks!

Mike

 

[WestTN]

AFC

When I made the first adjustment on mine, I took the cover off carefully and the tick mark was slightly past 12:00 o'clock. That is, the mark was slightly clockwise from the closest it could be to the valve cover. I bought the truck new and nothing had been serviced by anyone other than me. My vote goes for 'pointed at the vavle cover. ' The advice to just turn it will work well, too. The one thing I've never seen mentioned is "DON'T OVERTIGHTEN THE BANJO BOLT ON THE AIR LINE!!!!" This bolt is very thin walled. Take careful notice how loose the bolt actually is after breaking the paint loose.

Good luck.

After the changes on mine, (see signature) the old 1989 is capable of high 15's quarter mile times IF traction can be found.

 

[Shrimpy]

Hre is something that will set you staright every time when dealing with the AFC diaphram. When you remove the cap, go ahead and put a reference mark on the rubber piece and part of the metal housing it is sitting in. Then very CAREFULLY, pull up on the rubber diaphram and it will slide up. Look at how the shaft that the diaphram is connected to is tapered towards the bottom. I refer to it as being cylindrical, but slightly off center. It has a "deep side" and a "shallow side". You want to position it so that the deep side (the one that will allow the pin that rides on the shaft, to move the most) to be oriented toward the front of the engine (radiator). Mine was set just the opposite, it had the shallow side toward the engine allowing the pin to move the least. Now that everyone is thoroughly confused grab your tools and get to Work!!!!

 

[Scot]

Ok everyone keeps talking about the tick mark. My diaphragm has one on the top as you look at the plate, and one ~180deg opposite on the underside. It also does not corrolate to the taper as described in the instructions. One day I am going to pull that sucker down and take some good pics with a macro so we can all get on the same page.

 

[BushWakr - RIP]

Ok, so I'm not an artist Midnite, but I tried to cover the basics here for ya...

Hi Midnite,



Sent you an email on this but I think I'll try posting the drawing here to see if it works. I know, I know, don't quit my day job!!

 

[Shrimpy]

Excellent Post Bushwaker

I knew we had to have an artist somewhere on this board. Excellent post Bush !!!!!!! Anyone who is wondering, I don't have any "tick" marks on my rubber diaphram. The first time I popped the cover I simply marked the diaphram and the housing to give me a reference point. Then pulled out the whole diaphram and turned it so that the "Deepest" part of the shaft was pointed to the front of the engine and would allow the pin the most movement. Use this drawing and go slowly and you should be on the right track. Remember to make a reference mark when you first pop the cover and all should be well.

 

[Midnite]

Very cool--thanks BushWakr!



I've already rotated it 90 deg. and it definitely made a difference. Unfortunately it's mostly in the form of smoke, especially at full throttle. I think my 21 sq. cm. turbo housing and stock exhaust system is begging for modification.



Thanks again!

Mike

 

[BushWakr - RIP]

Midnite, you can control the smoke by adjusting the set screw on top of the afc housing. Loosen off the 13mm locknut and turn the center screw counterclockwise. It should be set to very near "neutral". In order to check it you need to remove the top of the housing and see if the housing wants to 'pop up' due to spring pressure. If so, turn counterclockwise some more. Mine just starts to make contact with the housing pressed down firmly in place. This was a suggestion made to me by Piers. Also, 90 degree rotation is about right to start with to see if your pleased with improvement. Remember, you need to confirm that you are not already at the 'max depth' setting, otherwise 90 deg. don't mean squat. If you go too far, you'll just end up "coming around for a second time" resulting in de-fueling rather than up-fueling.

Clear as mud, right!



PS, put in a "signature" to help with future questions as answers depend on what you've done or not done to ole Bettsy.