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Fuel pump tweaking


Well-Known Member
May 13, 2014
Country Flag
I've read the Lcool bible on this many times and have done the boost compensator mod (3 clicks) and done the off boost injection volume. I have also done the boost compensator profile change and this is what my question is about.

On Lcool it says:

"You can rotate the diaphragm past the max point. This now begins to reduce the fuel delivery. There are no markings to show where the maximum point is however you can feel where this point is.Rotate the diaphragm with your eyes closed (this is important) and feel the point where the tension is the least. Mark that point and perform that operation again to confirm the position. The diaphragm should be in the same position."

There are two points where the tension is least when rotating the diaphragm and using an analogy of going up a hill and then over the top: the first point is at the bottom of the slope just before you go up; the second is as you go over the brow and come down.

which one should it be adjusted to :think:

hope this makes sense.
Are you sure you havnt just rotated it full circle? I found it a bit hit and miss tbh, and took the top of the diaphragm off. So I could see what was going on. The plunger wil have to be ground down, or a difficult bolt undone on the front of the fuel pump to put the plunger back in.
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As I recall, you can rotate it all the way round full 360 but it goes 'on cam' and a bit stiffer to turn before going 'off cam' when it gets looser. I'm trying to figure whether I should set it to less tension on or off the cam.
I read that being off cam, "tension being the least".

With out having a look i cant remember what i did. Someone should chime in soon with a better memory..
Anyone else been there and done this and got the t-shirt ?
As you can see on the pic the plunger can only be "off cam" or "on cam" or ever increasing or decreasing increments inbetween. The increase in resistance felt when you turn the diaphragm is the profile of the cam pushing against the spring loaded horizontal pin. When the plunger is pulled out the spring pushes this pin out so that the plunger cant be pushed back in. So you either grind a smooth angle on the plunger, or remove a bolt behind the spring so that the pin can be pushed back without the load on it and the plunger will drop in. People dont seem to be aware of this method.

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