DI pump Internals
 

Getting tired of everyone armchair engineering the DI pump to death with out anyone knowing what is actually in the pump or how it differs from other DI pumps.

In the same sense that an Audi IC engine and a Subaru IC Engine are the same, and different so are the pumps. That is to say there are vast similarities, and they operate, fundamentally, on the same principals and are limited by the same obstacles.

I will share with you what I have found inside our pump, well I will share with you what is pertinent about what I found inside the pump in regards to the crickets that seem to upset everyone so.

http://i24.photobucket.com/albums/c9...od/pumpiso.jpg

It is worth noting, all critical component diameters are properly dimensioned in the solid model. I will share what clearances matter. I have not fully defined the casting or the cap at this stage because I do not care to focus the attention of this discussion on why this is apart or how the pump functions.

-the grey color represents the casting or the main body of the pump assembly

-The Yellow Color defines the Cap that is welded to the casting and contains the seal assembly. the cylindrical hole in the center is not actually cylindrical it is cone shaped with the smallest diameter (.263") being on the side opposite the casting, the diameter where the washer is contained is .587" diameter

-The Red represents a firm rubber like seal that has approximately .001" of "interference" with the pump shaft (it looks like phenolic in color but is clearly not a laminate or contain any epoxy). this seal is not possitively retained and has .014" of calculated clearance in the direction the pump shaft travels, it is limited in it's radial movement by an O-ring discussed below.

-The Blue represents the cricket...I mean...washer of doom. My sample pump (Thanks @robispec ) shows signs of this part being lightly swedged between the pump body casting and the Cap (it is unknown if this is a result of thermal expansion during operation of if this occurs during assembly in seating the cap to the casting, which is a pressfit interface prior to welding). This part has a clearance diameter of .273" in the center. the OD is .581" the face of the washer that faces the casting has 2 slots across it at 90 degrees to each other to allow any fuel that leaks past the pump to casting interface to pass down the void between the cap and casting to a hole in the casting allowing the fuel to return to the low pressure side of the pump (before the inlet presumably)

2 parts are not drawn here.
-1 there is an o-ring that fills the void surrounding the RED seal, it is held in quite snugly being a standard .094 (3/32") cross section O-ring and being stuffed into a void .060" on the radius and .120" in depth, this oring allows the pump seal (RED) to migrate slightly with the stiction of the shaft passing through it.

-2 the Piston it's self. Where it passes through the washer/seal/and cap is .256" dimeter The effective diameter of the pump where it enters the casting is larger than the seal diameter and the washer profile shows this larger diameter on the side facing the CASTING.


What you need to know.

The pump can only contact the washer (theoretically) at the bottom of it's stroke (piston as far out of the pump casting as it comes) and there is a witness mark indicating that this is not an abnormal condition.

The shaft of the pump can never touch the washer. The washer has .009" clearance to the shaft per side, the washer only has .003" per side of clearance to the cap so it cannot migrate far enough to chatter on the shaft as so many have "predicted".


-----I would tend to believe that there is some deformation occurring where the washer is trapped between the CAP and the CASTING which allows the washer to float some nominal amount with the constant pressure of the piston coming to rest on it as the pump returns to the bottom of it's stroke.


This is isolated from the internal seal, (and there is a valve stem type seal external to this internal seal) so it should not cause leaking.

The pump I have has been used with both E-85 and the countries shittiest gas (Calpis 91) the piston has a witness mark on it that matches the witness mark on the washer, but the plating on the piston (DLC) is still in great shape with no signs of flaking or chipping. I will assume at this point that this is the intended purpose of the washer, it would seem that the washer was meant to be restrained in the assembly, and the level of restraint maintained by each individual washer maybe the difference between a noisy pump and a silent pump. I have full confidence in the factory desing and see nothing to worry about in my findings. I will continue to run my noisy pump until...the next thing happens

TLDR; Go find another thread to shit on I would prefer only people who understand what I just wrote to comment or for those who would like clarification to ask.

legitimate TL;DR: the piston shaft never comes in contact with the washer. the issue is something else. skullworks believes it is the washer "floating" against the cap. noisy pumps vs silent pumps look to be a quality control problem.

Interesting stuff. I have witnessed the chirps seem to start after the engine has been running for a while. My best guess is the issue is temperature related, no doubt due to something expanding and then making contact/noise.

Any thoughts on why it would be intermittent? Or is it a luck thing: every time you start it up hope it stays stuck in the proper position and doesn't wiggle "free".

If the noise was driven strictly based on tolerances/quality that comes out within a temperature range it would be reproduceable relatively easily or at least predictably. All anecdotal evidence says that there is very little correlation with outside temperature, drive cycles or fuel used.

All I have to say is this:

:clap: Nice writeup :clap:

Ok, I have more to say. I appreciate this in-depth analysis, it only confirms what I have thought all along--that this is not something that I need to be concerned with, and that any desire to change it/fix it is "cosmetic."

Keep up the quality posts. :happy0180:

Thanks for the analysis. Are there any more in depth or exploded drawings of the pump assembly? I'm unfamiliar with DI pumps, but am very curious to learn, especially since the infamous crickets are the only problem I've encountered over nearly a year of ownership.

The biggest disappointment here is:

1. Someone providing quality content.
2. No coupler to connect and amplify the noise into the sound tube.

Thank you everyone for keeping this troll free....so far.


Will there be aftermarket...yes...
@Marchy , the piston of the pump when "retracted" rests against the washer it gets pushed into the grey area to displace fuel, no fuel is intentionally pushed "up" the shaft to where this drawing focuses it's attention.
@strat61caster I think it is manufacturing variance, there are alot of tolerances related to where the piston comes to rest at the end of it's stroke, so it may be that some pumps (unrelated to their own internals but rather the mounting pad height or cam lobe grind) may never seat against the washer at full retract (or the bottom of the stroke if you prefer) it may also be metallurgical, some batches of washers may be a better fit or some may be less prone to deformation due to temper or ??? your guess is as good as mine on that one...I'll need a larger lot than 1 pc to analyze to make any more educated stabs in the dark.
@wheelhaus not at this time...as I continue my development I may extract more data and try to help the community understand better this new technology...especially if we can keep the discussions on track...like we have here so far.

Thank you for doing the research and drawing this up..

Do you see anything that would make the "ethanol is the cause" plausible.. If not why do you think other countries do not report this problem? I love finding out this stuff, knowledge is power type stuff..

Or better yet, we have a guy that's on E85, no noise at all.. Switches to 91, immediately starts the crickets, do you have a theory as to why??

I will say this. Ethanol free gas appeared to help the problem. However I'm on my third full tank and the cricket sound came back with the vengeance this afternoon. With ethanol free gas. So I know what I won't be spending extra money on. :happyanim:

Thank you for the analysis and CAD model. Just curious what you based the model off of, obviously a pump, but did you disassemble it to make this model? And if so, can we see those pictures as well?

Any thoughts for people who had the chirps, switched to ethanol-free, and lost the chirps? I don't think that every other symptom should be written off as a coincidence at this point.