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Discussion Starter #1
I am getting code P0171 bank 1 lean. The fuel pressure is reading 35 psi.
I have replaced:
  • Fuel Pump (twice in case the new one was defective)
  • Fuel Filter
  • Pressure Regulator
I have done a voltage drop test. Fuel pressure is still low. Resets the code after about 5 minutes driving. What else is there?
 

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1995 T100 2WD
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I am getting code P0171 bank 1 lean. The fuel pressure is reading 35 psi.
I have replaced:
  • Fuel Pump (twice in case the new one was defective)
  • Fuel Filter
  • Pressure Regulator
I have done a voltage drop test. Fuel pressure is still low. Resets the code after about 5 minutes driving. What else is there?
O2 sensor, voltage to injectors, vacuum leak, EFI relay. I agree the fuel pressure is low but the P0171 code needs to be corrected and the fuel psi is only one symptom of many that can generate that code.

Besides the code and low psi what other symptoms are you experiencing? Did anything change after you did the work you did?
 

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Discussion Starter #3
I have checked the vacuum system and replaced the PCV valve. I had a bad O2 sensor and replaced it as well. Actually the O2 sensor was the first thing that had to be replaced. When that didn't fix the problem the next problem to come up was the PCV valve. After that I got to the fuel pressure problem. As far as I can tell it runs fine always has.
 

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1994 Camry V6 XLE-J
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was the new o2 sensor denso or bosch, etc? if not denso, that could be part of the problem.
i don't have my haynes in front of me but what is the idling psi supposed to be? if 35 is correct, then lean can be many other things. hold old are the plugs? when were the injectors pulled and spray pattern tested last? dunno if yours has an igniter but if it does, have you replaced it? if not, then it's probably got the coil in the distributor. has the disto been replaced recently?
did you verify you have 12 volts to the pump while it's running? were you able to put an ammeter inline and see if the current draw is correct for a working pump?
tony
 

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Discussion Starter #5
Denso O2 sensor and Denso fuel pump. I believe the correct pressure should be 50 psi. I did a voltage drop test at the pump with the pump running, less than 0.1 drop on the negative side. 0.3 drop on the positive side. Plugs are about a year old car has 250K miles on it I bought it used I assume none of the other items you spoke of have been done. I think I need to get the fuel pressure up before before moving on to the other items.
 

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Yes, that's low, spec is 44-50 PSI running, and at least 21 PSI after being off for 5 minutes.

Have you tried a different fuel pressure gauge?
 

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1994 Camry V6 XLE-J
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it sounds as if you don't have any drivability complaints unless i missed them, so i wouldn't be so worried about the psi numbers as that could be due to measuring equipment/setup as they don't give us a schrader valve on these cars so plumbing one in might cause some skewing of the numbers with smaller feeder hoses, etc.,

if it was me, i'd clean out the injectors and see if you can get the total trims numbers (short and long terms added together) under 10 percent under all combinations of loads/accelerator angle, etc. and see if that clears the lean code.

also, cleaning the maf wires with maf cleaner (if so equipped) will help with the lean code.

note: it goes without saying that all these assumptions are based on not having a kink in the fuel line anywhere from the tank to the fuel rail.
tony
 

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Discussion Starter #8
On the fuel pressure gauge, I looked at the cost of all the SSTs required to do the pressure check and decided to take it to the local service center. I have been thinking that I should observe what they are doing to see if they are following the prescribed procedure. In the manual none of the other fuel system tests are started until after the fuel pressure is established.
 
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