Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community - FT86CLUB - View Single Post - Fluctuating fuel pressure and fuel pump duty

1Saucyyy_brz · 04-23-2021, 03:16 AM

To give anyone reading this some background on my car. 63k miles, built motor and with rods and pistons, full blown motorsports turbo kit. 550cc injectors and AEM fuel pump.

So, ever since i got my car tuned a few months ago this issue has been happening. During light acceleration, the car runs really rich (in the mid 9's to 10's) and when i get into boost, the car runs on the more lean side (in the 13's and 14's). During the tuning process the car was only running rich, the lean issue came up later. At the time of tuning, the tuner thought that i just had a faulty AFR gauge and just told me to replace the gauge. After a couple weeks i replaced the gauge and the running rich issue was still present. Shortly after replacing the gauge, i got a SLIP and CEL light. The codes that were shown were P0456 (evaporative emissions system leak detected, very small leak) and P0441 (Evaporative emissions system incorrect purge flow), the SLIP was C1201. I left the lights there to see if they would go away on their own, didnt happen. After clearing the lights, they come back after a week or two.

A bit more information that might help: I have an ecutek blue tooth dongle allowing me to view in real time a lot of parameters for the car. So, while driving, I started watching a lot of the parameters to see if i saw anything out of the ordinary. What I saw was that the fuel pump duty would be at around 60% while the fuel rail pressure is at about 11.00 to 16.00 MPa. At first when i saw this I thought that maybe the fuel pressure regulator is bad and needs to be replaced, but my check engine lights are telling me otherwise. Another thing i noticed when i was watching over the parameters is that while casually cruising (60-75mph) the fuel pump duty would "flicker" between 60% and 75% just randomly and cause the fuel pressure to jump around with it.

So, what im wondering is that where should i start to tackle the problem? After doing some research I saw that a cracked or pinched line going to (or coming from) the charcoal canister could be the issue. I then saw that accessing the charcoal canister is a pain and involves dropping the rear diff. Another possibility that i saw was that maybe it is the fuel cap, which i can confirm is not the problem. The fuel pump is fairly new with less that 10k miles on it so i dont think its that failing on me.

Any and all information is helpful and i am wiling to answer any questions pertaining to the issue. Thanks in advance.

04-23-2021, 03:16 AM	#1
1Saucyyy_brz Member Join Date: Nov 2020 Drives: 460whp built turbo brz Location: Gardnerville Nevada Posts: 14 Thanks: 0 Thanked 3 Times in 3 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Fluctuating fuel pressure and fuel pump duty To give anyone reading this some background on my car. 63k miles, built motor and with rods and pistons, full blown motorsports turbo kit. 550cc injectors and AEM fuel pump. So, ever since i got my car tuned a few months ago this issue has been happening. During light acceleration, the car runs really rich (in the mid 9's to 10's) and when i get into boost, the car runs on the more lean side (in the 13's and 14's). During the tuning process the car was only running rich, the lean issue came up later. At the time of tuning, the tuner thought that i just had a faulty AFR gauge and just told me to replace the gauge. After a couple weeks i replaced the gauge and the running rich issue was still present. Shortly after replacing the gauge, i got a SLIP and CEL light. The codes that were shown were P0456 (evaporative emissions system leak detected, very small leak) and P0441 (Evaporative emissions system incorrect purge flow), the SLIP was C1201. I left the lights there to see if they would go away on their own, didnt happen. After clearing the lights, they come back after a week or two. A bit more information that might help: I have an ecutek blue tooth dongle allowing me to view in real time a lot of parameters for the car. So, while driving, I started watching a lot of the parameters to see if i saw anything out of the ordinary. What I saw was that the fuel pump duty would be at around 60% while the fuel rail pressure is at about 11.00 to 16.00 MPa. At first when i saw this I thought that maybe the fuel pressure regulator is bad and needs to be replaced, but my check engine lights are telling me otherwise. Another thing i noticed when i was watching over the parameters is that while casually cruising (60-75mph) the fuel pump duty would "flicker" between 60% and 75% just randomly and cause the fuel pressure to jump around with it. So, what im wondering is that where should i start to tackle the problem? After doing some research I saw that a cracked or pinched line going to (or coming from) the charcoal canister could be the issue. I then saw that accessing the charcoal canister is a pain and involves dropping the rear diff. Another possibility that i saw was that maybe it is the fuel cap, which i can confirm is not the problem. The fuel pump is fairly new with less that 10k miles on it so i dont think its that failing on me. Any and all information is helpful and i am wiling to answer any questions pertaining to the issue. Thanks in advance.