Fuel pressure loss at WOT!

Zayuh_ray

Zayuh_ray

Greenie N00B Member
Greenie Member
What's goin everybody!? First post but lets jump right in!
I've got a 2010 Mazda speed 3 with the mods listed
-3inch Cork sport intake
-CPE downpipe with full cpe triton exhaust
-Damond pcv plate routed to 2 catch cans
-Autotech internals with Cork sport rebuild kit and new PRV from Cork sport
-cpe front mount intercooler kit
-cst4 turbo from Cork sport
So now the issue is during WOT logs the HPFP act press will start around 1600+ but then when boost is introduced it will dip to 800 but then increase overtime in WOT. I've replaced the PRV with a new one from Cork sport in December and replaced the fuel rail sensor. I've rebuilt the entire HPFP with the Cork sport rebuild kit as well. I've had this fueling issue for about a year now and can't find out what's the issue. I've bought a new AEM fuel pump in hope that this may be the issue but i am still waiting for it. As im writing this tuner just told me its the internals or the cam follower/lobe.
 

Attachments

Have you done the hot engine HPFP pressure rise test? I see you replaced part, but did you test old and or new?
 
Lets start with this, what is cold key on pressure?
Is the spill valve plug clip broken? If so zip tie the plug as it can rattle and cause bad connection.
Chance spill valve itself can be failing " swap with a pick n pull cx7 one.
 
Yes! I do gotta figure out why its dropping pressure still, seems its dropping to 1200 but the immediately going back to 1600+
 
Check cold key on pressure, should be above 50psi, if its not then either fuel pump filter is clogged or failing fuel pump.
 
Okay, while i was swapping fuel rail sensors i do remember seeing 58-60. That was first crank on cold
 
How many miles are on the car? Could be time to change the in tank filter
 
It might be perfectly fine it might be the problem. Rule out the easier stuff first
 
Okay good! I have a new AEM pump here now and plan on installing it tomorrow! hopefully this solves my problem?!
 
The injectors are static flow, but the HPFP is not.
Around peak torque, depending on power or fuel flow levels, the HPFP cannot keep up. After 7k RPM, the stock internals can probably max the injectors (untested math based hypothesis) .

The fact that the pressure recovers at a similar or higher airflow suggests that the ITFP is feeding properly.
The fact that it's falling at all means the HPFP is not keeping up.

Questions (don't skip any):
What fuel are you using, and what oil?
Do you smell fuel in the engine bay when the engine is hot and running?
When was the last time you pulled the HPFP and checked the Autotechs for scoring or the spill valve for sticky and/or cleaned it?
 
@Enki I am currently using 91 from maverick and using liquid molly 5w40.
and I wanna say yes, there are times I smell fuel and cant find where its from.
I pulled it recently for cleaning, I'm gonna say 2 weeks ago and I have not checked them for scoring. but I can recall a time before about two months ago where I did check the internals for scoring there were none!
 
Check the HPFP hardline nut for a leak. If you managed to nick the tip on the hardline, you need to get a new one unless you can get it fixed by someone that knows how to fix it.

Not sure on the oil, if it's DEXOS equivalent you should be fine.

Recommend you get lighter fluid (naphtha) and clean the pump one last time (internals and spill valve are all you need to do), then lube and prime with Redline Injector Cleaner.
 
I hate to sound like a noob but where is the hardline you're referring too? please and thank you!
And will do tomorrow! I shall grab these items and get to cleaning the HPFP asap!
 
The line that you have to re-connect after taking the hpfp off and back on right? As I'm typing this yes it is lol, i can definitely check tomorrow if it does have any damage or not. Just for a what if, if it does have damage how do i go about that?
 
You must log in or register to reply here.
Back
Top