High Pressure Fuel pressure/Fuel filter questions

My Gen 1 has just about 150K miles on it (I bought it new in 09). During my last tuning session we noticed I am not always maintaining 1700PSI on my fuel rail during pulls. PRV test passes at over 1800 PSI. I have cleaned my dump valve a few times.

Could my in tank fuel filter, possibly be plugged? I have never changed it in 150k miles. I feel like maybe the low pressure side is not feeding enough to my high pressure side. I guess I could log the low pressure side and see if it's keeping up?

Thoughts?

 

I don't see anywhere on my Access Port where I can log my low pressure side. As I am reading around it looks like there are Deatschwerks and AEM in tank pumps that push 265LPH, 340LPH, and 365LPH.

What does the stock pump push? Any advice on the quality of these pumps? I can pull the pump out without dropping my tank, right?

 

Stock pump you should see between 45-70(ish) PSI on your supply. Just look at your HPFP actual before you crank the car/after sitting and cooled down for a while.

The AEM is the most used and reliable ITFP, I used it in my Gen 2 with no issues and it's an easy job.

You don't have to drop the tank, but you will have to trim some of the metal around the service access as the existing hole is not big enough to pull the pump assembly out of the tank.

 

OK, copy that. In the next couple weeks I plan to pull it out to check my filter anyway so I may just swap the pump, too, since I am in there. It would be nice to trim the panel before I open the tank (to keep metal chunks from falling in the tank). When I pull my seat up and pull the panel off, is it easy to see where it needs to be trimmed? After I trim it, does the access panel still cover the hole or do I need to seal that up somehow?

My fuel pressure issues only really ever show up when I am WOT for more than about 1.5 to 2 seconds. To me that sounds like the ITFP cannot keep up with the demand of the HPFP. I am hoping it's because the "filter" in my tank is getting fouled after 160k miles of fuel.

 

Yeah, you will easily be able to see what you need to trim. How you go about doing that is up to you. Air saw, air nibbler, or good ol' fashioned snips. Up to you. Depending on how big you trim the hole, you may need to figure out a solution to cover it back up. It overhangs a tad bit so you may be good, if not you can fab something up or you can use some ducting tape to make it work.

While it may be your fuel pump, your fuel relief valve may also be starting to die. Not many things can cause drops in fuel pressure.

 

That all makes sense.

I have run the PRV test a few times and it pops off at 1850 psi or so. My car runs good 99% of the time but at WOT for more than a couple seconds, injector duty cycle starts to climb (like mid to high 90%s), and pressure drops to 1000PSI or less. If I do 3/4 throttle or just normal driving, I have no real issues.

 

In your OP, you say "we noticed". Is that your tuner (freektune)? Does he know about this...just a thought.

Short of changing the in tank sock, the only other way to monitor pre HPFP is by gauge to be 100% sure.

Your spill valve also controls the fuel incoming to the HPFP.
read <here> if you like.

 

Yeah, he saw it first. It’s a little inconsistent. So I would run a log, he noticed it and gave me some suggestions to try, I would run a log, get good pressure on the log, he would send me a new tune, etc. i cleaned my dump, then replaced the dump valve, the removed the entire HPFP housing and cleaned it all, replaced the housing, and almost all the factory parts with a used parts, and still the same results. My internals look perfect, too.

 

Hopefully dumb question but you have a decent amount of gas in the car when this is happening right? If you don't have enough it will slosh back and can starve the pump

 

Tagging in here.

I am currently experiencing the same issue. Here is a picture of a log of mine. The fuel pressure bottoms out at 1005psi at 5500rpms, then climbs back up to to 1248 at the end of the pull.

The tank was full of fuel, it has corksport internals in it, the in tank pump is a walbro 255hp.

 

Not a dumb question. I am not the smartest person in the world and have missed simple things like this in the past. I get the same results regardless of fuel level.

 

Never hurts to check

 

OK, so I pulled my back seat up and took a look at it. By my judgement, it looks like this is about what I would need to cut. I really don't want to cut that much so I think I am going to just drop the tank. It's more work but I feel like I will be happier in the long run. I'll just plan to kill a Saturday swapping out the pump and filter.


I plan to order AEM part number 50-1220 pump. Do I need any other parts to make this swap? Like, I can use the strainer that comes with the AEM pump and skip the OEM strainer? Or should I go ahead and order a factory LFB6-13-ZE1 fuel strainer?

 

Order a factory filter. The AEM one isn’t a direct plug and play plus I like the OEM style tons more.

 

In JT's build thread he recommended this website for filter pickup strainers cheap. I used them on my AEM pump install and they fit. I also replaced the fuel pressure regulator while I was in there, not mandatory.

https://www.highflowfuel.com/quantum-fuel-pump-strainers-qty-3-for-mazda-speed-3-all-2007-2012/

 

OK, got all my parts (pump, Pickup strainer, and fuel filter body dealy).

Dropped my tank without drama. Then I spent 2 hours hammering away on retaining ring. it was absolutely seized on there. Yes, I bent the little locking tabs out of the way. After 90 mins of hammer and punch (and even tried an air chisel with a blunt tip). I broke pretty much EVERY single ridge off the ring. I got super frustrated and decided to just cut it off. (see pic) I bought this car new and it has never had the the fuel pump out so that was the factory torque on it.

After that, it was all easy. Check out how nasty my pick up filter was!

The AEM pump swapped out just like a replacement pump, just had to solder the wires. I have it all back together and am just waiting on the new retaining ring to get it tested. You know much those things sell for?! I paid $65 for it! ggrrrrrr...
Once it was all back together and sitting under my car I broke the filter body dealy open to inspect. It was full of fine black dust. It spilled out in the box (you can kind of see if in this picture).

The ring is supposed to get here Wednesday. Fingers crossed!

 

all buttoned up. Took it for a spin and so far everything seems good to go. I did one 3rd gear pull and fuel pressure stayed north of 1700psi so fingers crossed this was a solid fix. I have almost no fuel in my tank so I could not take a longer road trip to check it out.

If anyone else ever does this, the hardest part of dropping the tank, swapping pump/filters, and reinstalling is getting the fuel fill hose to seat all the way on the tank. There is almost no room in there to really push on the hose. I have mucho hand cramps from doing that, but other than that (and the fiasco with the fuel pump ring, Mazda Part number BN8F42167), this was not a hard job.

 

I’m thinking of replacing my pump as I’m getting a fuel issue as well. Where did you find information to know how to drop the tank i also don’t want to cut the metal?

 

If you become a metal member you have access to the shop manuals

 

...or youtube. I used that as a reference.