Fuel Pressure Issues

VersaTuner for Mazdaspeed6, Mazda 6 MPS, Mazdaspeed3, Mazda 3 MPS, CX7
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jlr8185
Posts: 6
Joined: October 19th, 2016, 11:39 am

Fuel Pressure Issues

Post by jlr8185 »

hey, i have a 2007 mazda cx7 gt with the 2.3 DISI turbo MZR engine. at idle the car is running around 300 psi in the fuel rail. the maps are targeting for 430 psi in fuel rail at idle. i have replaced the fuel pressure regulator on the fuel rail, the high pressure fuel pump, and all injectors with seals. car will run at idle but when the throttle is open (the pedal is pressed about 15 to 20 percent) the fuel pressure in the rail will drop from around 300 to about 130. with KOEO fuel pressure also reads about 300. with engine running and throttle opened very slowing the rpms will increase and fuel pressure will increase but never over about 700. i really need some help with this.....pls....
Dolfius
Posts: 64
Joined: May 31st, 2017, 2:54 am

Re: Fuel Pressure Issues

Post by Dolfius »

Either your Fuel Pressure Relief valve is bust (the brass nipple on the RH side of the fuel rail), or your in-tank fuel filter is clogged like a mofo.
jlr8185
Posts: 6
Joined: October 19th, 2016, 11:39 am

Re: Fuel Pressure Issues

Post by jlr8185 »

removed the fuel pressure relief valve (the brass thing) and it seems good (being that it is brand new), i cannot get any air to pass thru it either way. if i just turn the key to the on position the fuel pressure reading steadily climbs, i had it climb to the 500s the day before yesterday. i forgot to mention the mods on the car. Forge BPV, 3 inch ram air intake, EGR delete, VTCS delete, catless down pipe, and versatuner. also, i was wrong about the idle fuel pressure, it is more like 200 psi. I think i need to upgrade fuel pump internals. i just want to make sure there is nothing else that could be causing this issue before i get them.

thanks for the input, i would appreciate any input and/or thoughts
Dolfius
Posts: 64
Joined: May 31st, 2017, 2:54 am

Re: Fuel Pressure Issues

Post by Dolfius »

I doubt the HPFP internals will solve your problem though. They're meant to hold pressure better, not necessarily increase it. Idle pressure should be around the 400psi mark.

Have you checked the spill valve at all? The filter in the tank?

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jlr8185
Posts: 6
Joined: October 19th, 2016, 11:39 am

Re: Fuel Pressure Issues

Post by jlr8185 »

I have checked the spill valve. as far as i can tell it looks fine, all the pieces are there. i cleaned it and reinstalled it. is there any way to clean the intank filter??
jlr8185
Posts: 6
Joined: October 19th, 2016, 11:39 am

Re: Fuel Pressure Issues

Post by jlr8185 »

i think i have found the issue. while the car is idling, the hpfp spill valve voltage is 8V. i read in a MSF thread that it is supposed to be around 10V. can anyone confirm this or give more info on the spill valve voltage?? also, i unplugged my MAP sensor while the car was idling and there was no change in the idle of the car.....any thoughts???
mituc
VersaTuner guru
Posts: 1324
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Fuel Pressure Issues

Post by mituc »

jlr8185 wrote:I have checked the spill valve. as far as i can tell it looks fine, all the pieces are there. i cleaned it and reinstalled it. is there any way to clean the intank filter??
You should simply replace it with a brand new one.
jlr8185 wrote:i think i have found the issue. while the car is idling, the hpfp spill valve voltage is 8V. i read in a MSF thread that it is supposed to be around 10V. can anyone confirm this or give more info on the spill valve voltage??
If the relief valve is stuck open then the spill valve doesn't have too much work to do. Did you replace that relief valve already?
jlr8185 wrote:also, i unplugged my MAP sensor while the car was idling and there was no change in the idle of the car.....any thoughts???
The MAP sensor is there for protection. It doesn't have any impact in how the car idles or runs under normal load, the ECU will take countermeasures only when the MAP pressure reads reach or exceed the set values.
If you unplugged the MAPs sensor you will eventually get a check engine light for either open circuit on the MAP sensor or for lack of correlation between the BARO and MAP sensor reads. But even at that point the car will run absolutely fine. Right now my 3.5BAR CS MAP sensor is broken in my CX7 and I'm relying only on the load limits, everything is absolutely fine and the car drives very well.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
jlr8185
Posts: 6
Joined: October 19th, 2016, 11:39 am

Re: Fuel Pressure Issues

Post by jlr8185 »

thank you mituc for pitching in. with key on engine off the fuel rail pressure will build past 1000 psi and hold. however, when idling the fuel rail pressure is only 200. i checked the voltage being sent to the spill valve on the hpfp and it is only 8V. the manual says it should be around 10V. any ideas on what could be causing this??
Ivanshinoda
Posts: 1
Joined: July 3rd, 2021, 9:10 pm

Re: Fuel Pressure Issues

Post by Ivanshinoda »

Do you ever found the fix? Am in the same boat, MI spill valve connector is 8v when running, and 12v when disconnected
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