[SOLVED] Can't Hold Fuel Pressure

Back to the topic at hand, it looks like you can also pickup the entire OEM assembly for pretty cheap it looks like. It looks like it comes with the OEM pump itself, but I'm not 100% certain.

If I have no plans to go bigger power wise, would it be better to pickup an OEM unit rather than the AEM?

L34B-13-35ZA - OEM Mazda Fuel Pump
 
Update here. For better or for worse, the problem has gotten worse. Fuel pressure now dips to the ITFP pressure randomly, which previously led me to trying different spill valves. Since I've tried so many and it's unlikely they're all bad, I'm starting to suspect the wiring to be an issue now.

@Enki can you let me know what you think? Right around row 3000 my fuel pressure drops to ~60 under a constant throttle.

I assume a short or bad wire to the spill valve could cause it to not function properly.
 

Attachments

Tried the load test that's been recommended to me before, wires seem to be fine enough and the lightbulb stayhs lit
Enki said:
Could be the internals seizing too. If you still have your stock ones you can put them back in and see.

Too bad Derrick never responded.
Click to expand...
So I threw in an OEM pump, refurbished actually, and took the car out for a drive. To my surprise, no 60psi drops. Fuel pressure obviously didn't keep up with the demand at WOT, but I assume this is because of the OEM internals. Never had OEM ones before, so I'm unfamiliar with how they act. Datalog 462 is a nice long drive with the refurbished pump and OEM internals.

Additionally, I did the fuel pressure test with these internals and was quite surprised by how linear the pressure rose from the start. This is unlike my Corksport internals, which decreased for the first few minutes and then increased. I have no idea how this is possible.

Corksport internals (red, orange, dull green) versus OEM internals (lime green)
upload_2023-3-23_20-20-1.png

To be absolutely certain it's the internals and not the housing somehow, I'm going to swap the CS internals into the refurbished housing tomorrow and see if the issues comes back. If it does, I'll see if I can get my internals replaced under warranty.
 

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Not a great idea to do a WOT pull on stock internals, and I hope that isn't what you did in this log; doesn't look like it, but just checking.
 
Enki said:
Not a great idea to do a WOT pull on stock internals, and I hope that isn't what you did in this log; doesn't look like it, but just checking.
Click to expand...
Sorry I should have clarified, not WOT but just getting into boost and doing some pulls. That datalog was indeed the one, but like you said not really WOT just getting into it enough to see the pressure drop and then off the gas.
 
So I put the CorkSport internals back into the pump and took it for a drive, and sure enough the 60psi drops came back. I let the car cool down and threw the OEM internals back in, took her for a drive and no 60psi drops. It is definitely the CorkSport internals seizing up.

Also decided to do a fuel pressure test with the OEM internals from an idle, and the results were much different than the CorkSport internals from idle.

OEM internals in brown versus CorkSport internals in orange.
upload_2023-3-24_18-2-17.png

So what's next? Well, I will certainly try to get my CorkSport internals warrantied, but in the meantime I may scoop up a set of AutoTechs.

Questions I do have for anyone who could chime in:
  1. How do these internals get scored to begin with? (They are ~1 year old)
  2. How exactly do they seize up? The spring doesn't bring the piston back down to the cam bucket?
  3. How do the internals somehow change the fuel pressure test results?
Thanks everyone for helping out and I will update again when I get some new upgraded internals.

Attached datalogs:
  • 462 - OEM Internals
  • 464 - Switched to CorkSport Internals
  • 465 - Switched back to OEM internals
 

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When you contact corksport again Link this thread in the email as well. Sorry about the luck with the CS internals hopefully the warranty comes through they did seem suspect from the first pic you sent.... That being said I've seen auto techs fail too doesn't seem like either brand is failure free
 
Update, I received my AutoTech internals and installed them. Car now holds fuel pressure during WOT!

After having been so used to the CorkSport internals, I have to say that I 100% prefer the AutoTech internals. The retainer and keepers are SO much easier to work with than the factory one CorkSport reuses, and my socket FITS over the AutoTech retainer entirely allowing me so get full contact easier. No more having to compress the spring with the socket to get it to grab the bottom of the seal nut. It also took 3 seconds to install the keepers versus tapping the OEM tappet trying to get it to seat fully, which was super annoying.

Time will tell if I run into any issues and end up eating my words, but install wise AutoTech absolutely takes the cake. I have the CorkSport spring as well, but didn't install it so as to keep the changes between tests minimal, but I think I may throw the CorkSport spring into my pump with the AutoTech internals for the added beef.

I also decided to do another fuel pressure test from idle to compare, which yielded interesting results. Not sure what to make of them.
upload_2023-3-29_21-7-46.png

Last, I attached a 4th gear WOT log which felt absolutely great and showed substantial gains over my previous "OK" runs with CorkSport internals as of lately. All in all, I am super happy with finally having fixed the car and being able to floor it with peace of mind.

I can't for the life of me figure out how to mark this thread as solved, despite having done it in the past on other threads. :confundio1:
 

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Last edited by a moderator:
Ok ha I looked at your log and saw 20 psi and around 5k I knew it wasn’t stock. Right on man glad you got it figured out


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