aneroid diaphram and pin

[Baron]

A while back someone posted something about having bad mileage(like 16mpg) and had a mechanic open something up , somewhere on the pump and free up a pin that moves up and down as needed to adjust fuel supply( or something like that).

My mileage is constantly about 16 and I am wondering if I could improve it(most say that 18 to 20 is normal) by doing this procedure.

So can anyone offer a somewhat detailed description of this procedure??? thanks baron

 

[BushWakr - RIP]

Take a peek here, you'll find a bit of info on were, what, etc.



https://www.turbodieselregister.com/user_gallery/displayimage.php?&photoid=2494&width=2



Baron, if your truck is stock then you should be getting a bit better mileage than 16mpg. It is more likely not the fueling pin that is the problem. That pin will actually cause underfueling if sticking, not overfueling as I understand it.

Make sure your fuel filter is not plugged (replace it), your air filter is clean and, run a good dose of fuel additive thru the truck if you haven't done so.

The mileage can be affected by the pump settings of course. If no one has been into the pump then you can improve your mileage by making some adjustments to it.

If you look at the picture the link takes you to, you'll see the pin you're talking about. It comes in from the left side and touches the "cone" in the center.

You need to take the top off the AFC housing to see it.

There are 4 screws that hold the AFC housing on. Also you need to undo the boost tube that is attached to the AFC housing (right side) and swing it out of the way.

Take a look at the pics in my "VE Gallery" and you'll get a feel for what's what.

Once you have the top off the AFC, you mark the position of the diaphram at the 12:00 position. (The top edge toward the engine rocker covers. )

Then remove the diaphram by pulling it up. If it's a bit sticky coming out that is a good indication that the pin is protruding as it should be. If that is the case, the pin is sticking out, and contacting the cone as shown in my picture.

Take care lifting it out, so that you can look at the cone end, and see if there is a "witness mark" on the cone. If so you'll see the mark indicating were it has been rubbing on the cone, and from there you can tell how much fueling has been happening in relation to max/min setting. (Look at picture and you'll see the "offset" of the cone. )

When the diaphram finally pops out, the pin will have dissappeared into it's hole. Slowly cycle the throttle open and eventually the pin will pop back out of it's hole so you can see it.

To put it back, just use a small flat blade screwdriver and push it back in. If it won't come out by cycling the throttle then it's sticking.

It can be a booger to free up, and usually means the o-ring around it has hardened up and is getting tired.



If you want to make adjustments to the pump itself, first find out were things are set now. Mark the starwheel at 12:00 just like the AFC diaphram and we can go from there.





Bob.