Can't build fuel pressure past 400 PSI

[lQuantum]

Year/Make/Model: 2012 Mazdaspeed 3
Mileage: 120,000
Location/Alitutude: Dayton, OH (sea level)
Concern: Can't build fuel pressure past 500 psi while driving
DTC's: P0301, P0302, P0303, P0304
Modifications: CS intake & TIP, Mishimoto FMIC, CPE DP, MAC EBCS, CS HPFP internals & injector seals
ECU/Tuning Software: Cobb Accessport V3
Tuner: Freektune
Is the concern intermittent? No
Can you duplicate the concern? Yes
Recent Repairs: Reinstalled all intake parts multiple times, replaced spark plugs multiple times, replaced coil packs, installed CS injector seals
Correction: Took apart HPFP, cleaned everything up, and made sure the nut that holds the internals in place was torqued to spec. I don't know how to change the title of the post to add the corrected tag

Howdy! I've had my speed for about 2 years now. 6 months in, I get HPFP internals & the o-ring set & install everything except for the spill valve o-rings for some reason. Then I get all of the bolt-ons seen above and get a tune from Justin. Everything is fine for a couple of months until I suddenly get an LTFT of -6 to -10. It sits around there and fluctuates occasionally. I pulled apart my intake several times and could never find a leak, and also I replaced my injector seals with CS ones and scrubbed the injectors with a scotch brite. They didn't look very dirty. The Spill valve ground LOOKS fine.

Fast forward about a year to a few months ago and I start getting stuttering at takeoff. I replace the spark plugs and all seems fine for a bit, and then the issue comes back and I also can't hit full boost - I'm limited to about 13 PSI even though I'm tuned for 21. Then I start getting misfire codes, P0301 - P0304. I replace plugs again and coil packs and no change. I look at my HPFP actual pressures and I'm sitting at 150 at idle, 400 at cruise, and I struggle to hit 300 while accelerating. When I do the KOEO test with a hot motor, it doesn't spike at all, just sits at 150. If I turn the key on with a cold motor, I get about 90 psi from the in tank fuel pump. I don't know if that's acceptable or too high.

So today I replace the PRV with an OEM one, no change. Then I pull off the spill valve, clean it up, replace the o-rings, smash my finger so bad that I might've broken it, and go for a test drive. The parts in the spill valve seemed fine, weren't crazy dirty, and all moved freely. Everything was exactly the same, fuel pressures don't change. Except that after 5 minutes or so of driving, my LTFT had been sitting at -5 and suddenly spikes to -11. It sits there as I drive home. Then I immediately do a KOEO test and the pressure spikes to about 500 psi - and then with KOEO, I watch it slowly rise up to over 900 over the course of a couple of minutes. That's... literally impossible, right? Without the cam turning in the HPFP, the pressure shouldn't be able to rise above the ITFP pressure which was 90 psi beforehand, right?

So now I'm not sure how to diagnose further. I'd love to not have to cut a hole in the body of the car just to check the ITFP, but I'm not sure how to diagnose it. The fuel pressure rising during KOEO seems strange but feels like it could be a red herring, idk. I think it could be indicative of a failing pressure sensor on the fuel rail. I switched to FPS voltage on my AP for a bit and it sat around 0.65 volts, that seems low? But I'm not sure where it should be.

Anyways, I'd love to grab a log tomorrow, but what parameters do I need to log? I have the parameters that Justin requested for tuning set right now. I'll also double check values for everything and get pictures / videos of my AP during. And also, does anything I've said here stand out as an indicator of a specific issue to anyone? My next guess is fuel pressure sensor, but I'd like to figure out how to diagnose it properly before throwing parts at it.

 

[Easter Bunny]

The fuel pressure rises after shutting the car off due to the heat in the motor
You need to take apart the hpfp and clean and lube everything

 

[Mtnbker3531]

Couple of things, first what do your STFTs look like? Your LTFT is using STFT to try and compensate for whatever error you have.

When you are looking for a leak in your intake system you would be much better served by smoke testing than attempting to disassemble everything and visually inspect.

What coil packs and plugs did you use? If the coil packs are anything other than OEM they can cause issues. These engines tend to be rather finicky aftermarket coil packs and sensors.

Cleaning the injectors with scotch Brite does noting for injector cleaning/performance on these cars. If you believe you have an injector problem you should have them replaced or professionally cleaned and flow tested. If they have never been done at the mileage you are at it's overdue.

 

[Enki]

Everything is fine for a couple of months until I suddenly get an LTFT of -6 to -10.

After uninstalling and reinstalling the intake, you may well have fixed a leak. The LTFT numbers you've listed are looser than most tuners will get them, but debatably within spec.

Fast forward about a year to a few months ago and I start getting stuttering at takeoff. ...I look at my HPFP actual pressures and I'm sitting at 150 at idle, 400 at cruise, and I struggle to hit 300 while accelerating.

That's for sure low. This tells me you either have an ITFP issue, need to pull and clean your HPFP alltogether (remember it's not just the spill valve that can get gummed up) or some other sensor/electrical issue. Easiest way to diagnose ITFP is to get in the car after it's sat cold for several hours and log the key on event (don't start it) and see what the rail pressure is. Anything between 40 and 60 is normal, below that and there's an issue (though, there could be an issue with flow, it seems kind of unlikely in your case).

Then I immediately do a KOEO test and the pressure spikes to about 500 psi - and then with KOEO, I watch it slowly rise up to over 900 over the course of a couple of minutes. That's... literally impossible, right?

No, this is normal. With few exceptions, things get bigger when they get hot (water being one, where the opposite is true). In a hydraulic system, the fluid is incompressible, so when the pressure rises, you're actually watching it heat up. The fact that it went and stayed over 900 PSI suggests that the PRV isn't the issue (at least below 900 PSI, anyways).

Anyways, I'd love to grab a log tomorrow, but what parameters do I need to log?

When in doubt, log everything and let us sort it out.


Additional questions:
1. What oil are you using? Be painfully specific here. This is actually important.
2. What fuel/mix are you using? This is also important.

 

[lQuantum]

Thank you all for the replies!

You need to take apart the hpfp and clean and lube everything

Gotcha, will do tonight.

Couple of things, first what do your STFTs look like? Your LTFT is using STFT to try and compensate for whatever error you have.

I haven't looked at STFTs, I was under the impression that you should always use LTFTs since STFTs fluctuate so much. Will check them tonight with the logs that I get.

When you are looking for a leak in your intake system you would be much better served by smoke testing than attempting to disassemble everything and visually inspect.

Yeah... I have an air compressor but no plug for it, I have to rewire my garage electrical to get it running. That's why I haven't done one yet That's on my list.

What coil packs and plugs did you use? If the coil packs are anything other than OEM they can cause issues. These engines tend to be rather finicky aftermarket coil packs and sensors.

I used the recommended NGK coils and plugs gapped to 0.026" as recommended by Justin. NGK 48859 coils and NGK 6509 plugs

Cleaning the injectors with scotch Brite does noting for injector cleaning/performance on these cars. If you believe you have an injector problem you should have them replaced or professionally cleaned and flow tested. If they have never been done at the mileage you are at it's overdue.

Good to know! That's also on the to-do list, I was under the impression that the low fuel pressure would point away from the injectors being the problem. I need to do them, absolutely, but would that cause the hpfp pressure to be so low? Maybe, I don't know.

That's for sure low. This tells me you either have an ITFP issue, need to pull and clean your HPFP alltogether (remember it's not just the spill valve that can get gummed up) or some other sensor/electrical issue. Easiest way to diagnose ITFP is to get in the car after it's sat cold for several hours and log the key on event (don't start it) and see what the rail pressure is. Anything between 40 and 60 is normal, below that and there's an issue (though, there could be an issue with flow, it seems kind of unlikely in your case).

I did the KOEO test yesterday before starting the car and I believe that I was getting 90 psi from the ITFP. I'm gonna double check that tonight, but I think that was the number that I saw. I've heard mixed things about whether or not having a higher ITFP pressure is okay. Like I said above, I plan on opening up the HPFP again (all the way) and re-cleaning / lubing everything.

No, this is normal. With few exceptions, things get bigger when they get hot (water being one, where the opposite is true). In a hydraulic system, the fluid is incompressible, so when the pressure rises, you're actually watching it heat up. The fact that it went and stayed over 900 PSI suggests that the PRV isn't the issue (at least below 900 PSI, anyways).

When in doubt, log everything and let us sort it out.

Gotcha! Like I said in the OP, I did just replace the PRV yesterday with a new OEM one so I don't think the PRV is the issue anyways. Of course, it could be faulty or I could have boofed the install somehow, those are both always possible. I will update my AP recording parameters to all parameters before collecting logs.

Additional questions:
1. What oil are you using? Be painfully specific here. This is actually important.
2. What fuel/mix are you using? This is also important.

1. MOBIL 124315 (Full Synthetic) Mobil 1 Advanced; Full Synthetic; SAE 5W-30. Filter is WIX 51348XP (High Performance / Heavy Duty) XP Extreme Duty. I believe that's the only oil that I've put in the car, and I've used a bosch filter before I believe - but I don't remember which one.

2. Straight up 93 octane from the pump, usually from Shell or Caseys.



Thank you all for the input, I have a few steps to take now and will update after opening up the HPFP, inspecting the internals, cleaning & lubing everything, and then taking logs of KOEO before & after the drive as well as a test drive. I also ordered the fuel pressure sensor, as it seems to be a relatively easy replacement and was about $60 or so which is insignificant compared to the amount I've spent chasing this issue already. I might also call around and find a shop with a smoke tester that I can drive to, I'm out in the country though and I'd be nervous to drive the car more than a few miles so I'll have to do my best there. The car has been problematic for 90% of the time that I've had it and I seriously appreciate you guys helping me to get this issue sorted. I will update when I get my first round of stuff done, I hope to have that done tonight but it might also be tomorrow.

 

[Enki]

I haven't looked at STFTs, I was under the impression that you should always use LTFTs since STFTs fluctuate so much. Will check them tonight with the logs that I get..

Personally, I use a formula, which is LTFT + (STFT/2), but I also have a curve smoother to make sure shit doesn't go wonky. Since you have a tuner, this is more his problem than anything else; just listen to what he says and do what he asks of you.

I did the KOEO test yesterday before starting the car and I believe that I was getting 90 psi from the ITFP. I'm gonna double check that tonight, but I think that was the number that I saw. I've heard mixed things about whether or not having a higher ITFP pressure is okay. Like I said above, I plan on opening up the HPFP again (all the way) and re-cleaning / lubing everything..

90 PSI is technically high and could point to either the pump or pressure regulator in the basket being modded. Also, keep in mind that you don't need to take everything off the HPFP; just do the following:
1. Disconnect wires/hoses/etc from the HPFP; make sure engine is cold or you can get some fuel spray. If engine is not cold and you want to do this anyways, have the car idling, disconnect the electrical plug on top of the pump for the spill valve and then shut it off. It won't hurt anything and will drop rail pressure to below 100.
2. Use a 32mm wrench or modded socket to loosen the spill valve(don't remove yet); this will further reduce pressure. Also make sure you do the zip tie trick on the hard line to make sure the nut doesn't drop into the void, cause that's ass.
3. Remove HPFP from the engine
4. Break the internals loose using a vice and an 18mm (iirc?) deep socket. This piece and the spill valve are the only things you need to remove from the pump.
5. Clean everything using lighter fluid/naptha, as I find this to be the best cleaning agent.
6. Relube using redline injector cleaner and reassemble, leaving spill valve loose
7. Reinstall on car, connect all hoses and lines but remove the spill valve once more. Be careful reconnecting the hardline, as nicking the tip or bevel on the hardline means replacing the entire hardline. I learned this the hard way.
8. Fill the pump up with redline injector cleaner to the lowest (towards front of the car) bottom thread of the spill valve
9. Reinstall spill valve and tighten
10. Reconnect spill valve plug
11. If you've done everything right, the car should start on first crank like nothing changed, as it's been pre-primed and the residual injector cleaner will hang out in there providing lubrication and cleaning action.

Gotcha! Like I said in the OP, I did just replace the PRV yesterday with a new OEM one so I don't think the PRV is the issue anyways. Of course, it could be faulty or I could have boofed the install somehow, those are both always possible. I will update my AP recording parameters to all parameters before collecting logs..

PRVs are simple check valves, so even a tiny bit of dirt can cause a new one to "fail."

1. MOBIL 124315 (Full Synthetic) Mobil 1 Advanced; Full Synthetic; SAE 5W-30. Filter is WIX 51348XP (High Performance / Heavy Duty) XP Extreme Duty. I believe that's the only oil that I've put in the car, and I've used a bosch filter before I believe - but I don't remember which one.

2. Straight up 93 octane from the pump, usually from Shell or Caseys..

You may want to swap to a different oil if it's not on the list of oils here in the oil thread that someone will probably link you to after this post. If this is a dexos oil, you should get a UOA done and post it in the thread for analysis.

The reason why is because the right oil will literally make or break your engine on this platform. Worst HPFP I've ever seen I bought online and it was from a CX7 that only ever saw pump gas...It was so badly gummed up, they took the part that the pump bolts to off the head and sent it with the pump because it wouldn't come off. And the stock internals, which you can normally just yank out the back of the pump by hand were seized....All of this was caused by oil.

Thank you all for the input, I have a few steps to take now and will update after opening up the HPFP, inspecting the internals, cleaning & lubing everything, and then taking logs of KOEO before & after the drive as well as a test drive. I also ordered the fuel pressure sensor, as it seems to be a relatively easy replacement and was about $60 or so which is insignificant compared to the amount I've spent chasing this issue already. I might also call around and find a shop with a smoke tester that I can drive to, I'm out in the country though and I'd be nervous to drive the car more than a few miles so I'll have to do my best there. The car has been problematic for 90% of the time that I've had it and I seriously appreciate you guys helping me to get this issue sorted. I will update when I get my first round of stuff done, I hope to have that done tonight but it might also be tomorrow.

You need to be careful with the fuel pressure sensor, as normally, that's a part that comes with the rail. Honestly, it's fine to have it, but I'd sit on that part until you know for sure you need to swap it. Logs are probably the most important thing, after cleaning the HPFP.

 

[lQuantum]

So... I was following all instructions, and Enki I'm glad you said this when you did:

Break the internals loose using a vice and an 18mm (iirc?) deep socket. This piece and the spill valve are the only things you need to remove from the pump.

Because I was in the process of trying to get the little retainer off the CS internals and was having a hell of a fight with them when I got the notification of your comment. So I cleaned everything out, put it all back together, and the car runs great. My fuel issues are fixed, I have boost, I have no misfires or stumbles. I THINK the problem was that when I did it originally, I didn't torque down the nut that holds the internals in place. That or, the fact it was dirty actually did clog it up. Although I don't know about that because it really didn't seem dirty.

Anyways, thank you all for the help, I learned a LOT while working on this issue and finally have a problem I've been chasing for a year fixed. I guess a healthy doubt in your own work is good, and something something the easiest explanation is usually correct. Gotta go delete these logs now because they're embarrassing lmao

 

[Enki]

I forgot to mention you don't need to torque the internals. When I do this, I just hold the pump in my hand and hit the socket wrench with my other hand a few times to make sure it's snug. Don't need a vice to get it out after that, and it's never backed out on me (nowhere for it to go, really).

 

[lQuantum]

I forgot to mention you don't need to torque the internals. When I do this, I just hold the pump in my hand and hit the socket wrench with my other hand a few times to make sure it's snug. Don't need a vice to get it out after that, and it's never backed out on me (nowhere for it to go, really).

Hmm... Well, I torqued it to 40 ft lbs like the corksport instructions said to, hopefully I don't need to pull them back out any time soon. I think I'd cry. Maybe the issue really was that it was dirty and not the nut like I thought, in which case I'll be sure to check recommended oils next time I change it. The good news is, if I do have fueling issues later on, I know so much more about how these fuel systems work after this fiasco.