Hiya fellas,
I got a weird one here that I can use your help with. I hope I've laid out a nice case for y'all!
Problem: my Torque app has been showing LTFT over 15% consistently for a while, and I've also been getting "fuel too lean" codes so I started to dig into this issue. With a turbo, running too lean puts us on edge.
So, I installed a fuel pressure gauge on the inlet of the fuel pump. This eliminates a dirty fuel filter (which is less than two years old) impacting the gauge reading. Sure enough, the fuel pressure at idle was 28psi. Disconnect the vac hose from the FPR and pressure went up to 35psi.
Internet says:
For your 1996 1FZ-FE, the FSM fuel-pressure specifications are:
So, my fuel pressure is way off and I started some troubleshooting by going to my local buddy's place who has a '96 80 series NA with the original FPR. His numbers are exactly as shown above, so I figured if I stick his FPR into my engine, then I'll get the same psi reading. His pump resistor has not been bypassed so his pump was able to achieve those numbers with 9vdc (low speed mode).
Here's another kicker: when my FPR was installed on his engine, he wasn't able to get the FSM numbers which leads me to blame my FPR, which was installed with the turbo back in 2021. So, it's five years old. When his FPR was installed on my engine, it wasn't able to get the FSM psi numbers. Put his FPR back on his engine, and BAM, his has the FSM numbers.
Some things I've tried:
- bypassed resistor - no change in PSI.
-swapped out fuel pump relay with buddy's- no change in PSI. Still, I have a brand new one coming from Japan as a PM.
- ran a fused wire from battery straight to the pump POS wire - no change in PSI.
- used a bike pump to apply positive pressure to the vac port of FPR, and the pressure went up to 45psi. The more I pumped, the more PSI came out of the FPR.
- pinching the return line from the FPR to the tank bumped up the pressure to 45psi, so the pump (less than two yo) has no problem achieving a higher PSI.
- pump fuel sock is brand new when the pump was swapped out, less than two years ago.
-LTFT is now less than 10% with the pump resistor bypassed, which I shouldn't have to do but it's a temp bandaid for now.
-two weeks ago I got misfires from ALL cylinders. This tells me I don't have all six failing injectors, but something common to all six cylinders is the issue
- i have no intake air leaks/ or pirate air using a smoke tester.
-I also have no exhaust air leaks before the upstram O2 sensor (air/fuel ratio sensor)
-the fuel pressure doesn't nose dive under hard accels.
New issues, and perhaps related but these seems electrical, not mechanical:
The engine suddenly stalled on me while driving on a dirt road less than 20mph. The EFI fuse did blow so I'm investigating this on a parallel path. I might have an intermittent short around the fuse block under the hood. The CEL did not light up during engine cranking so that was my clue the EFI fuse blew. New EFI and COR relays coming from Japan.
Also, this happened twice so far: she cranks but doesn't start. Checked under the hood, nothing is amiss, tried again, and started up no issues. No blown fuses. Fuel pressure was 30psi each time so the pump was working fine.
If you're still with me, thanks for reading this long post. I'm sure I'm missing something obvious but my brain isn't able to figure it out.
Pump, fuel filters < 2yo
FPR = 5yo
FP relay+EFI+COR relays - all original, but will be replaced as a PM.
I got a weird one here that I can use your help with. I hope I've laid out a nice case for y'all!
Problem: my Torque app has been showing LTFT over 15% consistently for a while, and I've also been getting "fuel too lean" codes so I started to dig into this issue. With a turbo, running too lean puts us on edge.
So, I installed a fuel pressure gauge on the inlet of the fuel pump. This eliminates a dirty fuel filter (which is less than two years old) impacting the gauge reading. Sure enough, the fuel pressure at idle was 28psi. Disconnect the vac hose from the FPR and pressure went up to 35psi.
Internet says:
For your 1996 1FZ-FE, the FSM fuel-pressure specifications are:
| Test condition | FSM specification |
|---|---|
| Engine running, FPR vacuum hose disconnected and plugged | 38–44 psi |
| Engine idling, FPR vacuum hose connected | 31–37 psi |
| 5 minutes after shutting engine off | ≥21 psi |
So, my fuel pressure is way off and I started some troubleshooting by going to my local buddy's place who has a '96 80 series NA with the original FPR. His numbers are exactly as shown above, so I figured if I stick his FPR into my engine, then I'll get the same psi reading. His pump resistor has not been bypassed so his pump was able to achieve those numbers with 9vdc (low speed mode).
Here's another kicker: when my FPR was installed on his engine, he wasn't able to get the FSM numbers which leads me to blame my FPR, which was installed with the turbo back in 2021. So, it's five years old. When his FPR was installed on my engine, it wasn't able to get the FSM psi numbers. Put his FPR back on his engine, and BAM, his has the FSM numbers.
Some things I've tried:
- bypassed resistor - no change in PSI.
-swapped out fuel pump relay with buddy's- no change in PSI. Still, I have a brand new one coming from Japan as a PM.
- ran a fused wire from battery straight to the pump POS wire - no change in PSI.
- used a bike pump to apply positive pressure to the vac port of FPR, and the pressure went up to 45psi. The more I pumped, the more PSI came out of the FPR.
- pinching the return line from the FPR to the tank bumped up the pressure to 45psi, so the pump (less than two yo) has no problem achieving a higher PSI.
- pump fuel sock is brand new when the pump was swapped out, less than two years ago.
-LTFT is now less than 10% with the pump resistor bypassed, which I shouldn't have to do but it's a temp bandaid for now.
-two weeks ago I got misfires from ALL cylinders. This tells me I don't have all six failing injectors, but something common to all six cylinders is the issue
- i have no intake air leaks/ or pirate air using a smoke tester.
-I also have no exhaust air leaks before the upstram O2 sensor (air/fuel ratio sensor)
-the fuel pressure doesn't nose dive under hard accels.
New issues, and perhaps related but these seems electrical, not mechanical:
The engine suddenly stalled on me while driving on a dirt road less than 20mph. The EFI fuse did blow so I'm investigating this on a parallel path. I might have an intermittent short around the fuse block under the hood. The CEL did not light up during engine cranking so that was my clue the EFI fuse blew. New EFI and COR relays coming from Japan.
Also, this happened twice so far: she cranks but doesn't start. Checked under the hood, nothing is amiss, tried again, and started up no issues. No blown fuses. Fuel pressure was 30psi each time so the pump was working fine.
If you're still with me, thanks for reading this long post. I'm sure I'm missing something obvious but my brain isn't able to figure it out.
Pump, fuel filters < 2yo
FPR = 5yo
FP relay+EFI+COR relays - all original, but will be replaced as a PM.
