If we have some extra length between the spring installed height and the bind height vs the lift of the cam lobe, a shim would likely fix it.

We'd have to know the cam lift to have an idea about this. It's not simple to measure or even tell how deep the piston moves or how much the spring is compressed when the piston is fully out. Although with some calipers you can get an idea - just have to be able to turn the motor slowly (by hand).

If trying a shim, I would only try it at the top of the pump, not at the retainer at the bottom. The shim can't too thick or the spring will pull off the top as well and you definitely don't want that.

What would have caused the noise to start "all of a sudden." I have a hard time believing the spring deformed or shortened during a run. Only plausible thing is that the bottom retainer slowly wore loose.

I agree with Lex here. If the spring did/doesn't fit VERY snugly to the OD of the retainer raised section, it WILL vibrate in use and cause wear on either the retainer and/or the spring ID itself. I would expect to see the wear if you removed the keeper and spring to inspect them at the retainer end.....


The HPFP is a high-speed precision-clearanced device. There is a plethora of failed attempts to create what we have today. EVERY attempt has met with several failures before any sustained success. A thorough web search provides tons of information on inventions/patents, etc. trying to develop/improve upon the design. Ours is a single piston design, but there are several mutli-piston HPFPs in use as well.....

There is wear on the spring seat at the retainer from the spring not fitting snugly and moving against the retainer. I wish I snapped more pictures.

The question is - where do we go from here?

At first look, I think CPE should produce a retainer with the correct ID to support their larger piston/spring OR use a piston/sleeve combo closer to those used by the "other" kit suppliers with OEM spring. The OEM spring has proven to be just fine in supporting the larger capacity piston. The further we get from the OEM design, the more problems we'll have. IMO, the aftermarket (even at CPE prices) just doesn't have the resources to adequately test/develop this part........

It's true with most aftermarket parts. This is especially difficult to produce due to the tolerances and design. It's a complex part as you mentioned. One thing to make a downpipe and another to make an HPFP.

So you're right, either redo the retainer but it has to be done to OEM spec or it will fail like the competition.

Or reuse the stock spring. That means the top mount and perhaps the piston itself will have to be redesigned like the competition with just the top of the piston being thicker.

Sure, people can opt for one of those from someone else but I've read WAY too many stories of seized pumps.

On top of that - the piston that is only thicker at the end suffers from less lateral support in the bore. This causes more lateral forces on certain parts of it leading to scuffing and ultimately failure. There's a reason the stock piston is the same diameter throughout. The CPE pump is closest - it's just the detail at the retainer.

If the spring is worn at the retainer then ide say we have our answer, I had been thinking that it wasnt worn lol.

I bet they can design a new retainer that uses the OEM button.

I've heard that before.

Thanks for updating the OP. This is good info.

We don't have an upgrade for the spring right now. We have not seen a reason to add the spring due to anyone being able to confirm that the OEM one is not up to the job.

Fewer windings, it must have a larger diameter wire? If I were to build a custom wire spring it would have the same amount of windings, but with a higher tension wire to increase the spring tension.


How does the lateral laoding happen? The piston cup that rides on the cam follower can only move up and down, there is not lateral loading at the push end of the pump, so if the pump is not being pushed laterally how could is all the sudden be getting lateral loads in the pump?

What do you want tested? We are 4 to 6 weeks out on having our own testing staition ready for the pumps. Let me know what you want tested (post in our section) and we will get to it0.

Bova, any progress on checking out the cam follower?

yeah i'm a slacker, i'm still trying to find my e8 torx

Hahahahaha... Keep looking, its around there somewhere.

Lex, does your pump rattle when you are idling and you turn the steering wheel left to right? My PTP pump started making a similar rattle on initial throttle application from a 700 RPM idle or causing the power steering to kick in while idling.

It holds pressure fine, and the problem isn't always reproducible but I have noticed it. This does have me slightly concerned.

Yup, it happens when there is a pressure spike. So turning the steering wheel or tipping in causes it.

I can hear mine in any gear if I coast at low enough RPM and just tap the gas. There's a quick rattle as pressure builds.

mine has done that from day one, mr lil guy pump

So I guess it's an annoyance, but it's still safe to drive around like this right?

more or less yes. i found my e8 torx bit but haven't found the time to take the pump out. maybe tomorrow.

Do it bova! Mine's been rattling since I started this thread. Pressure is fine - rattle is the same.

I hear mine now...in fact I've heard it way before and thought it was the axle...thanks for all the work Lex! (again!)

my pump is definitely high mileage...but pressure is good, for now.

I also hear it at lower speeds when I tip-in from a coasting condition.

definitely...that's in fact when I hear it the most, tip-in @ cruising.

it's almost like a signal to not lug the engine...

How many miles on your pump Fobio? Would you be willing to pull it out and take some pictures of the cam follower (both sides), the pump button, and the seat the spring rides on?

I got the pump used...I figure the pump prolly has over 60,000 km on it when I got it...and I've went and put on another 25,000 km more...

unfortunately, I don't plan to wrench on the car anymore this season (all underhood parts are installed and waiting for suspension only now) as the rest of the time will be spent on suspension work.

if however, the chance comes up, I'd do it...

So how's the rattle club doing a month after the last post in this thread? Still getting this rattle here. Car still runs great.

rattle and running fine as always

the one rattle that pisses me off, that i plan to take care of tonight or tomorrow is my exhaust rattle on the stupid ms6 fake tips.

Hahaha... i always thought it was my tips rattling too, but turned out to be the muffler back there hitting a weld seam in the under carriage.


I fucking hate rattles.

I fixed a rattle last night...it was the hatch's weather stripping that had a slight flip on it and wasn't pushing against the headliner...unkinked it and rattle gone...

pump rattle still there. no change in pressure or how the car runs.

You run your A/C much Lex? I noticed mine rattled almost constantly at idle with the A/C on. The pressure was around 530 or so IIRC.

Lex, any updates with your conversations with CPE?

Have they read about your latest discoveries and acknowledged/confirmed your findings?

Thanks for the great thread guys!! So the noise is the only downside of the CPE then? It sounds like you'd have to listen for it, or never play the radio to notice this sound.. is that right? I've had two PTP pumps shit the bed, so I'm leaning towards the CPE pump, but considering KMD internals as well. Can you hear that noise at tip in while cruising w/ the windows down, or only at Bova's daily stops at Jack in the Box? lol I keed I keed. Honestly, I just want a fucking pump that works and holds pressure well... if I don't hear it inside the cabin, the I could care less.....

I am interested in buying a HPFP, and CPe is my main choice. But kinda holding back to wait and hear if CPe has anything to say or what they are willing to do about this.

I have heard nothing more from CPE. It does seem the rattle is a common issue with their pumps but I don't think anything will be done unless failure (wear on other parts, loss of pressure) starts to become an issue.

No, the pump does not rattle constantly for me, just when there is a rise in pressure. If I listen carefully without music, I can hear it every tip-in such as during gear changes. The noise has maintained the same intensity. I will be taking it off the car again in more miles to check for wear etc.

IMO the CPE pump is the best pump on the market with the least catastrophic failures so I would not hesitate getting it over something that may seize.

yeah the pump only makes noise on rise in pressure and i don't think it is just cp-e, as i have a pump from PG which were kmd internals at the time i think. it runs great but just makes that noise on pressure rise.

and douge, we don't have jack in the box here in pittsburgh, so that ain't it, haha.

I believe the common denominator is the upgraded spring and button fitment which must be there for the CPE pump. Read my writeup on the issue.

I've been through a couple PTP pumps, and it's time to move on to the CPE pump instead. I just got a new stock pump from PTP (+ refund soon), and I put it on yesterday. And what do you know? It rattles like some of the aftermarket pumps. I just wanted to let you guys know it can happen on a stocker as well! I started a new thread on the MS6 section and linked them here in the OP. I've read this entire thread before, and I find that it's not that loud, and it doesn't bother me. This sounds like the other vids to me:

Rofl today I had my RPM's just right at the Wendy's drive thru (A/C on, steering wheel slightly cocked). The guy taking my order couldn't understand me over the horrible rattle. I had to turn the A/C off to get it to stop.

That sounds horrible.

What happening with this tread ? We lost lot of post ?