Low fuel pressure at idle

[racersir]

Hey guys,

Just a couple of hours ago on my way to work I noticed the speed was not boosting and my fuel pressure is low at idle is in the 70’s psi according to the dashhawk. The car is idling and running fine except for the no boost and the low fuel pressure. The pump and internals are stock is 2007 Speed 3. I was thinking possibly of the relief valve. Any thoughts? Thanks in advanced.

[Hathor]

Has it been hot lately?

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[racersir]

No, everything has been normal

Originally Posted by Hathor Has it been hot lately? Sent from my SM-G935T using Tapatalk

[Hathor]

Low fuel pressure? Trouble code
This may help.

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[racersir]

Did a test drive again dis time got a code p300 and pressure didn't go above 80 psi while driving. But car drives and idles fine except the no boost. I stopped the car until I get this figured out. I'm thinking my HPFP internals went to shit

[mituc]

Originally Posted by racersir Hey guys, Just a couple of hours ago on my way to work I noticed the speed was not boosting and my fuel pressure is low at idle is in the 70’s psi according to the dashhawk. The car is idling and running fine except for the no boost and the low fuel pressure. The pump and internals are stock is 2007 Speed 3. I was thinking possibly of the relief valve. Any thoughts? Thanks in advanced.

Take the pump out, replace the FRV and the pump internals. 60-70PSI is the in-tank pump pressure, so things can go bad quite easily.

[Vansquish]

Originally Posted by mituc Take the pump out, replace the FRV and the pump internals. 60-70PSI is the in-tank pump pressure, so things can go bad quite easily.

Whoa there. That's a little too much too quickly.

First things first, @racersir; do the KOEO test. This will help you determine whether or not the HPRV (high pressure relief valve, located on the fuel rail) is damaged. If it is, THAT is what you should be replacing.

Until you know whether the HPRV is damaged, there's not much point in replacing the spill valve (which is what's on the HPFP, @mituc), nor replacing the HPFP internals.

Of course, replacing the HPFP internals with Autotechs or the like isn't a bad idea either, as they'll give you more headroom to play around with if you should ever decide to do so.

[racersir]

I did the KOEO and pressure never went over 160psi. I just now took out the HPFP but need to get a depper 18mm socket to dissamble. I have the internals ready to install and see if that fixes the problem. Anything in particular that I should be looking for when I dissamble the pump? Or any other ideas? Thanks to all for your help.

[IQUOTE=Vansquish;3120270]Whoa there. That's a little too much too quickly.

First things first, @racersir; do the KOEO test. This will help you determine whether or not the HPRV (high pressure relief valve, located on the fuel rail) is damaged. If it is, THAT is what you should be replacing.

Until you know whether the HPRV is damaged, there's not much point in replacing the spill valve (which is what's on the HPFP, @mituc), nor replacing the HPFP internals.

Of course, replacing the HPFP internals with Autotechs or the like isn't a bad idea either, as they'll give you more headroom to play around with if you should ever decide to do so.[/QUOTE]

[Phantom240]

Did you ever get this sorted out? My girlfriend's car is doing the same damn thing. She even went out and bought (against my advice) a brand new HPFP from Mazda and I put it on today. Still no more than 70ish psi at any RPM

[Vansquish]

Originally Posted by Phantom240 Did you ever get this sorted out? My girlfriend's car is doing the same damn thing. She even went out and bought (against my advice) a brand new HPFP from Mazda and I put it on today. Still no more than 70ish psi at any RPM

REPLACE THE FUCKING HPRV. If your HPFP pressure is never going above 70psi (or 130psi as you wrote in your other thread) at KOEO, then the HPRV is dead. Replace it. Period. The end.

Originally Posted by racersir I did the KOEO and pressure never went over 160psi. I just now took out the HPFP but need to get a depper 18mm socket to dissamble. I have the internals ready to install and see if that fixes the problem. Anything in particular that I should be looking for when I dissamble the pump? Or any other ideas? Thanks to all for your help.

Replace the HPRV (high pressure relief valve). It is located on the fuel rail on the front driver's side of the motor.

The part number for the valve is: L3K9132J0

[Thor Hammer]

Originally Posted by racersir I did the KOEO and pressure never went over 160psi. I just now took out the HPFP but need to get a depper 18mm socket to dissamble. I have the internals ready to install and see if that fixes the problem. Anything in particular that I should be looking for when I dissamble the pump? Or any other ideas? Thanks to all for your help.

Vanquish told you EXACTLY what to do, and what to replace. Then you look right past it and say your're going to replace the fuel pump internals. LMFAO! Come on man. Vanquish knows this platform very well. Perhaps you don't know that yet. Just do what the man says and all will be well.

[Phantom240]

Sheeeit, mine certainly wasn't the HPRV

[Vansquish]

Originally Posted by Phantom240 Sheeeit, mine certainly wasn't the HPRV

Damn! I'm sorry to hear that. I just saw that you're having trouble with your PCM. Here's hoping you can get it figured out!

[racersir]

I changed the HPRV and I'm still getting only 60 to70 psi, pressure come back to normal and intermittently goes back down to 60-70 any other ideas. The HPRV is Brand New OEM and the I changed my pump for another pump that was supposedly working fine on another MS3 before taking off. Any help please. Thanks

[racersir]

With the brand new OEM HPRV the pressure now it no climbing above 60 in the KOEO test now I'm lost I did try to blow thru the HPRV and air goes on one side only, I did the same test with the one I removed and had the same results also. Any other ideas?

Originally Posted by Vansquish Whoa there. That's a little too much too quickly. First things first, @racersir; do the KOEO test. This will help you determine whether or not the HPRV (high pressure relief valve, located on the fuel rail) is damaged. If it is, THAT is what you should be replacing. Until you know whether the HPRV is damaged, there's not much point in replacing the spill valve (which is what's on the HPFP, @mituc), nor replacing the HPFP internals. Of course, replacing the HPFP internals with Autotechs or the like isn't a bad idea either, as they'll give you more headroom to play around with if you should ever decide to do so.

[mituc]

Originally Posted by racersir With the brand new OEM HPRV the pressure now it no climbing above 60 in the KOEO test now I'm lost I did try to blow thru the HPRV and air goes on one side only, I did the same test with the one I removed and had the same results also. Any other ideas?

So let's get this straight: you now have a new HPRV and you also tried with another HPFP (which should rule out the spill valve issues), and still get the same low FP at idle, right?
Where there any parts swapped from your pump to the test pump you used?
When you monitor does the fuel rail pressure spike or vary in any way (when you blip the throttle or just idling)?

[racersir]

Yes the HPRV is new and the pump was swapped with another pump and I'm still getting the same intermittent issue when is reading 50-70 psi it doesn't vary when I hit the gas just stays between 50-70. I'm really confused at first I thought the 2nd pump that I install could be bad as well but now that I did The KOEO test the pressure never went above 60 psi. I don't even know what to do next

[racersir]

I should probably add the car ran fine for a couple of days after installing the HPRV then today while cruising in the freeway the pressure started to drop to 50-70

[SpoolinSpeed3..757]

Originally Posted by racersir I should probably add the car ran fine for a couple of days after installing the HPRV then today while cruising in the freeway the pressure started to drop to 50-70

Is there a weird grinding/screeching sound coming from your hpfp when your fuel pressure drops? If not I would start looking at the pressure sensor on the fuel rail

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[racersir]

Everything seems normal. I know Mazda doesn't sell the sensor but does anyone know if you can get the sensor alone I read is a Bosch unit and it had this number on another post 0261545006 can anyone confirmed by any chance if this number is correct Bosch 0261545006?

[mituc]

Nah... that sensor is press fitted there with pretty high precision. One skilled individual can swap it with a good part but Mazda usually sells the whole fuel rail with that sensor and in the service manual marked that part as not serviceable.

I don't think you will find that Bosch part# either, it's most probably a part manufactured for FoMoCo.

I was about to point to the FRP sensor (sensor itself, harness, and so on) as well after finding how you swapped the pumps. However, it's weird that after changing the PRV everything was fine for a few days. I'm thinking that most probably that's a coincidence though.

[racersir]

A couple of people have changed just the sensor. I'm might try the sensor since I can't seem to find anything else wrong with car? Any other suggestions?

[Dolfius]

You can get just that sensor from PartsBOS, based in Latvia, search using that part number.

I ordered one when my rail sensor shit the bed. The codes it usually gives is either fuel rail pressure sensor high circuit input, or low circuit input.

Now, having said all thát, I've just reassembled everything after a head gasket replacement, and now I'm getting the same low pressure at idle problem. When I blip the throttle, it shoots up to 250-300psi for a split second, then drops back down to 50-70psi. I don't know where/what to check anymore.

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[Themajinmazda]

[QUOTE=racersir;3120181]Hey guys,

Just a couple of hours ago on my way to work I noticed the speed was not boosting and my fuel pressure is low at idle is in the 70’s psi according to the dashhawk. The car is idling and running fine except for the no boost and the low fuel pressure. The pump and internals are stock is 2007 Speed 3. I was thinking possibly of the relief valve. Any thoughts?

I just solved the same issue by replacing my HPRV, I was at 70-130 idle fuel pressure and now I see 420-500 constantly (edgeautosport has them for $172). Even if you have replaced the HPRV before this I would look into it again, may be possible it shit the bed like mine did( I broke my HPRV during a flat foot shift ). I know for a fact it's not a spark issue with the low fuel pressure #'s like that