Fuel Pressure
#1
Fuel Pressure
I'm checking fuel pressure on a 2008 Impala 3.5L Flex fuel.
What value should I expect when:
1. Ignition ON engine OFF? [I'm getting 60 psi]
2. Switching from the above state to Ignition OFF? [I see an immediate drop to 57 psi, then down to about 52-54 psi after 5 minutes]
3. The engine is ON and idling? [Not yet measured]
I'm doing these checks to follow up on a P0172 (Fuel Trim Rich) condition. I expect to post more on that later.
Thanks for any feedback!
What value should I expect when:
1. Ignition ON engine OFF? [I'm getting 60 psi]
2. Switching from the above state to Ignition OFF? [I see an immediate drop to 57 psi, then down to about 52-54 psi after 5 minutes]
3. The engine is ON and idling? [Not yet measured]
I'm doing these checks to follow up on a P0172 (Fuel Trim Rich) condition. I expect to post more on that later.
Thanks for any feedback!
#2
CF Monarch
I'm checking fuel pressure on a 2008 Impala 3.5L Flex fuel.
What value should I expect when:
1. Ignition ON engine OFF? [I'm getting 60 psi]
2. Switching from the above state to Ignition OFF? [I see an immediate drop to 57 psi, then down to about 52-54 psi after 5 minutes]
3. The engine is ON and idling? [Not yet measured]
I'm doing these checks to follow up on a P0172 (Fuel Trim Rich) condition. I expect to post more on that later.
Thanks for any feedback!
What value should I expect when:
1. Ignition ON engine OFF? [I'm getting 60 psi]
2. Switching from the above state to Ignition OFF? [I see an immediate drop to 57 psi, then down to about 52-54 psi after 5 minutes]
3. The engine is ON and idling? [Not yet measured]
I'm doing these checks to follow up on a P0172 (Fuel Trim Rich) condition. I expect to post more on that later.
Thanks for any feedback!
#3
Thanks, oilcanhenry! The 2008 Impala 3.5L has port injection, so it looks like it's capable of the correct pressure. Any idea about the specification on holding pressure?
#4
CF Monarch
methanol would be.
#6
tech2, thanks for the suggestion!
My fuel composition reading is incorrect. I monitored it after the last fill-up (from near empty) and saw it changing (in the 70%-85% range), but it still settled at a very high number. I have confirmed MAF, MAP, IAT, ECT, HO2 sensors and my STFT is generally in the 5 to -10 range. LTFT is generally -15 to -30. Compression tests are in the 170-190 psi range. Spark plugs are consistent and look ok.
I have seen more than a couple of car owners follow the path of a fuel composition value reset (including in the Uplander forum) only to have the value to return to a high value days later. So, I'm a little skeptical of resetting the values, when (if all is working properly), the fuel trims and fuel composition values should correct themselves. If hypothetically, I have the fuel trims and composition reset and then the P0172 reappears, what would be the likely causes?
I have no other fault codes and have checked everything else I can think of, including the purge solenoid and vacuum lines.
Looking forward to any feedback you might have.
My fuel composition reading is incorrect. I monitored it after the last fill-up (from near empty) and saw it changing (in the 70%-85% range), but it still settled at a very high number. I have confirmed MAF, MAP, IAT, ECT, HO2 sensors and my STFT is generally in the 5 to -10 range. LTFT is generally -15 to -30. Compression tests are in the 170-190 psi range. Spark plugs are consistent and look ok.
I have seen more than a couple of car owners follow the path of a fuel composition value reset (including in the Uplander forum) only to have the value to return to a high value days later. So, I'm a little skeptical of resetting the values, when (if all is working properly), the fuel trims and fuel composition values should correct themselves. If hypothetically, I have the fuel trims and composition reset and then the P0172 reappears, what would be the likely causes?
I have no other fault codes and have checked everything else I can think of, including the purge solenoid and vacuum lines.
Looking forward to any feedback you might have.
#7
Reset the Alcohol composition and fuel trims. There was an immediate improvement.
Alcohol content went from 75% to 1.2 %.
LT fuel trim went from the 25-30% range to 9-12% range. So, there is still a problem to be addressed. I expect with a low LT fuel trim, the alcohol content will be incorrectly calculated at the next fill.
Alcohol content went from 75% to 1.2 %.
LT fuel trim went from the 25-30% range to 9-12% range. So, there is still a problem to be addressed. I expect with a low LT fuel trim, the alcohol content will be incorrectly calculated at the next fill.
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