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Hi, just wondering if anyone has done a fuel pressure test on their 2007-2009 RX 350. I guess any other Toyota or Lexus with a 2GR-FE engine would count as well. I'm running into P0171 and P0174 codes (running lean on both engine banks), and would like to hook up a fuel pressure gauge to verify good fuel pressure, but don't know where to hook a pressure gauge up to.
I did see a page here that illustrates hooking up a fuel pressure gauge to a "fuel tube", but not sure where that is exactly. In the engine bay, or near the fuel tank or underneath the car?
I think the 2004 RX330 I have does not have a fuel pressure test port. The factory manual calls for an adapter to be put in line for such a test.
I would make sure that you have no air leaks first or loose/broken hoses. ALso clean MAF sensor with MAF sensor cleaner, as MAf may be indicating low air flow because it is dirty, but oxygen sensor would indicate more air than reported by MAF, thus the lean code.
Also low fuel pressure could cause a lean code or clogged fuel injectors. That would be another step, thus your fuel pressure test.
Thanks Eddiev1. I only had a basic code reader at the time of running into the P0171 and P0174 codes. I have since purchased a live data OBD scanner (Bluedriver), and I now also have a VCI cable and Techstream, though I don't know how to use the software all that well.
When the lean codes first appeared, I sprayed the MAF sensor MAF cleaner and reset the codes. At that point, the car ran absolutely fine, though the codes came back. The RX350 has been getting progressively worse, to the point where it cannot be driven. I can only start it up and have the engine hold an idle until warmed up, at which point it eventually stumbles and dies. I tried driving it around the block, but all I could do was put the car in drive, and let the engine drive the wheels at idle--there is very little to no response when stepping on the throttle.
Bluedriver scanned P0102 and P0113 when the engine died at one point, which led me to replace the MAF with a new one (part # 197-6110, 22204-31020). The car still runs the same, though. I also replaced the PCV valve with a new OEM one, though that made no difference. I did notice that the PCV hose and some other vacuum hoses are pretty loose: I can easily yank them off and slip them back on by hand, with the clamps still in place on the hoses. I'll replace the loose hoses and change the OEM clamps with worm clamps, then will try smoke testing for air leaks with a Stinger pro, to look for leaks in the vacuum hoses.
I am not sure if vacuum is really the issue, though, since I checked STFT and LTFT live data with bluedriver last week, and saw that both the STFT and LTFT values at 1500+ RPM were about the same as they were at idle, which I recall was STFT at 20%, and LTFT at 35%. Thus the reason why I started this thread, asking for advice about fuel pressure testing
Is STFT and LTFT the same for both banks? Also, the trims would go down at higher RPMs if it was a vacuum leak, since vacuum leaks have less effect at higher RPMs, if I understand correctly.
It does sound like a fuel pressure or delivery issue, since the car stumbles and turns off.
Another item would be a leak in exhaust, but maybe you can check that when you get smoke machine.
Keep us informed, I like to understand how vehicles work to maintain a good running vehicle and to pinpoint issues.
Yes, STFT and LTFT are about the same for both banks. Correct, fuel trims go lower, even negative if the issue is a vacuum leak, and I was not seeing that with live data readings while revving the engine in park.
The car only threw the lean codes after I filled up the tank with premium gas at Costco, so I wonder if the gas was fouled with something. I'll update this thread with what I find out.
Posting a quick update. The car is still running into the P0171 and P0174 codes. At this point, the car still cannot be driven (no response from throttle when in drive). I can only cold start the car and have it idle for about 15 minutes until it warms up, then it will die, and will refuse to start up again.
Smoke testing: I smoke tested the engine by plugging in my Stinger Pro smoke machine to the PCV valve hose--I plugged the smoke machine up to the side with the PCV valve, and blew smoke into the engine. No leaks spotted--all the smoke ended up coming out the intake opening above the front grille.
I pulled out the back seats from the car and fuel pressure tested the pump with a fuel pressure kit that I borrowed from O’reilly. Was able to tee into the outlet and see only 10-12 PSI of fuel pressure from the pump. I checked the resistance on the pump’s +/- leads, and got a reading of 38 ohms, which is way higher than the 0.2-3.0 ohms as specified in the 2GR-FE service manual. So I loosened the fuel retainer ring, pulled out the fuel pump assembly, and replaced the fuel pump with a new OEM pump. Unfortunately, that still didn’t make any difference in the car’s behavior.
I need to pressure test again with the new fuel pump, but I am thinking the codes are due to a low fuel pressure situation. I am guessing that the pump is not getting the proper voltage that it needs to supply 44+ psi of pressure with the engine on. I did notice the voltage at the fuel pump connector is 11.5 volts with the key to the on position, but engine off. I don't know if the fuel pump resistor is factoring into that voltage drop during start up. Need to do more voltage testing while car is running, and check the fuel pump ground. I will also voltage test the relays, and do some voltage drop testing from the engine room relay box to the fuel pump connector. New pump is showing .7ohm resistance btw, when hooked into the fuel pump assembly wiring harness
tomr51, I installed a new fuel pump and it came with a new filter (the flat strainer that's under the fuel pump). I wonder--would a failing fuel pressure regulator reduce fuel pressure? The FPR is a part of the in-tank fuel pump assembly.
The fuel pump wiring diagram shows 2 different voltages, one for starting, a different one after running. Interesting, please let us know what you figure out, I'm a bit suspicious of mine too:
Are there wiring diagrams available on this site? I actually went ahead and signed up for one month of membership on Toyota TechInfo (https://techinfo.toyota.com), and while that was expensive ($75 for one month of access), it has provided me access to the RX 350's electrical wiring diagram in full color (the wire colors!). That alone has been worth the money, since I can trace wires accurately through all circuits. Plus, access to the RX 350 service manual itself is valuable, though alot of crossover information could be pulled from this online 2GR-FE manual: http://mr2.bordeauxgroup.com/AVTO0566.pdf
About the fuel pump voltages: I got the following from the RX350 repair manual on toyota techinfo.
Fuel Pump Control Circuit
The fuel pump relay switches the fuel pump speed according to the engine conditions. The fuel pump operates when the ECM receives the starter-operating signal (STA) and crankshaft-rotating signal (NE).
The fuel pump relay is turned ON while the engine is idling or operating at low load. This causes current to flow through the fuel pump resistor to the fuel pump. The fuel pump then operates at low speed. The fuel pump relay is turned OFF while the engine is cranking or operating at high load. The fuel pump then operates at normal speed.
So basically, the fuel pump should be seeing full battery voltage while cranking the engine (minus voltage drop from the circuit it runs through, which I'm guessing ought to be 0.5 volts or less), since the fuel pump resistor is not in play while cranking. When I have a chance, I'll measure voltage at the fuel pump connector (disconnected) while cranking. I think my DVOM has a hold button, so I can capture the voltage on my own.
I took the day off to figure out the issue, and thankfully, I finally did. I discovered that I forgot to install something on the fuel pump: an o-ring that helps seal the fuel pump's pressure within the assembly. Without it, the fuel pump was basically leaking within the tank. I did connect a 5ft. long 1/4" fuel hose to the outlet on the fuel suction plate, placed the other hose end into a bucket, and ran an active test with Techstream. It looked like the pump was spitting out fuel fast enough, but I didn't know for sure. Lucky for me, I had the absolute luxury of discussing the issue with a Lexus technician who has tremendous amounts of experience, and happened to go throught the same thing that I did when installing another pump on a car in the past. So he basically hit the nail on the head when he asked about the o-ring. You can see where it is in the pic below. I incorrectly assumed that the new pump that I bought came with the o-ring (it comes with the spacer, and I thought there was an o-ring in it) but it does NOT. So remember to purchase a new o-ring if you're doing an ala carte fuel pump repair on a Japan-built RX 350 (or you can re-use your old one if it's still good). If you have a North American built RX 350, it so much easier since you can simply purchase a fully-assembled fuel pump assembly to replace your old unit.
Before adding the o-ring that I missed, I went so far as to voltage drop test the positive and negative side of the fuel pump on the connector side. I am surprised that there was barely any voltage drop at all. I didn't care to test resistance on the relays, because they looked pretty clean and I was getting the voltage I expected at the fuel pump connector anyway.
o-ring installed within the fuel pump housing. This seals the fuel pump pressure within the assembly and allows proper fuel pressure to build in the entire fuel line.
Techstream showing good numbers for long term and short term fuel trim values. What a relief!
Techstream is slow at reading codes, and even worse for reading live data values. Bluedriver, an OBDII/Bluetooth scanner, is great for reading codes and live data to ensure that your car's components are running with values according to factory/service manual specifications.
Good detective work, and glad you got it figured out. Nice that initial clues about fuel pump turned out to be correct after all, #1 suspect for lots of folks I think.
So the problem is the fuel pump ? I also have lean condition on almost all RPM. Like +7% LTFT. No vacuum leaks. Smoke tested it. Brand new Upstream Lambda sensors and MAF. Fuel regulator is also changed with new. As i read fuel pump also is superseded with new model.Also changed injectors seals with all seals on the intake.
04-10-18, 12:17 AM
test fuel pressure on 2008 RX 350
