Possible fuel issues

2008 mazda speed3 99k miles. I bought the car a few months ago. It ran great put 3k miles on it. Bought ap for it and a few weeks later it started to stumble. Just once at first then over the next week it would stumble then throw a cel for fuel rail pressure sensor low voltage. I would clear the code and it wouldn't come back for a few hours. Then it would don't and stall the car. Several times on a 15 min drive. So I'm not driving it now. I read and read forums for days. Replaced the sensor now. I don't get a cel but it leaned out at wot all the way down to 300psi. Before all of this it would stay at like 1860 at wot. Any help is appreciated and keep in mind I'm very new to this. Thanks

Also should note I never noticed the hpfp being this chattery, and I feel like I'm hearing a wierd noise only when pressing the gas pedal.

 

Have you upgraded the HPFP internals? That should be done before the access port.

Have you cleaned the HPFP and replaced all the internal seals?

Have you cleaned the spill valve?

 

Im not too sure what was already done since i have only had the car for a few months. i got the ap so i could see that the fuel pressure was safe. and being that it was so high at wot with the cobb stage 2 tune and would spike llike 19.2 psi of boost at that point then it has internals. im new to all of this . i guess i need to pull the hpfp and check all of that out?

is it possible that i was having those issues and that cel for the pump not performing correctly?

 

Just cause you're hitting 19 psi of boost doesn't mean you have upgraded internals in the HPFP. The point of upgrading them is because the valve itself is weak and doesn't keep the pressure high in the fuel rail. You should have around 1700-1800 psi at WOT. It shouldn't drop down that much

You can remove the pump and then disassemble it to inspect the valve. If it's aftermarket there should be laser etched markings on it from whoever made it such as Corksport etc.

 

Correct. That will be my next step. I know the boost has nothing to do with fuel pressure. I was saying I imagined it does have aftermarket internals because at wot building 19psi it still would hold over 1800psi before this started.

 

The other thing I'd do is double check that the ground next to the hpfp is clean and snug also do the prv test

 

Ok so I just did the prv test and 1060 was all the higher it went then started falling.

 

If car was hot when you did it then that's a failed PRV time to replace it
Part # L3K9-13-2J0
https://edgeautosport.com/mazda-oem...7-2013-mazdaspeed-6-2006-2007-cx-7-2007-2012/

 

I don't believe I had it up to operating temp. But it had been running for a few minutes.

 

Engine should be at temp, how much is it going to throw off the test if it's not, I'm not sure. PRV isn't too bad to replace but 70$ part, so up to you if you want to just replace it or repeat the test with the engine at temp ( appreciate it's hard to run right now).

Also ensure that ground by the hpfp is clean and tight if not already done so

 

yea. i already have it out and ordered a new one . but it wont be here until the 27th. wasnt too bad to get to. i need to check on that ground. just a quick scan over the area around the hpfp i dont see a ground.

 

ground near hpfp is Circled in red, one lone black wire

 

everything looks good clean and tight on that ground . i was looking for it on the side of the head. not the top. lol but thanks for the input. guess im waiting for my new prv now..

 

Would appear so, let us know how it goes

 

will do thanks for the help thus far.

 

Ok so the prv came early. Installed and put back together. While doing this I found that my turbo inlet pipe was not clamped on lime at all. On the tube side. Too much air maybe why it was leaning out also? I'll drive it tomorrow and see how it does. It does some screeching at start up...?

 

Un metered air can certainly cause lean, boost leak test may be a good idea. What's screeching? Could be as simple as serpentine belt or tensioner / one of the pulleys

 

im not sure what the noise im hearing is. sounds like metal on metal... not tooo sure. only lasts for a few seconds. also this morning i took the car to work. no cel or anything runs well but leans down to 900 at wot.

which i guess is better than 300. lol it wasnt spitting and sputtering

 

Does it sound like slapping? Could be your timing chain hitting your valve cover, only way to truly check would be to pop off the VC and check it for marks and check chain slack at TDC. Is it only at start up? Not saying pop VC yet just looking for more info

Might be worth cleaning your spill valve as well. With that one coupler loose you need to check all of them - boost leak test would be good

@L337TurboZ @Easter Bunny thoughts?

 

Yea I was telling my wife that. I'll have to make an adapter to do this I guess? There are no tuner shops near me.