Hi guys , I wonder if you guys have any ideas what could be an issue... I have 2011 Lexus is250 F-Sport , recently I had an engine light come on and giving me a code of low fuel pressure on the fuel rail and engine running lean. We have cleaned the metal mesh on the fuel tank pump and also changed the filter on that pump and checked the pressure and it is 2 bar. And it sounds like it is on good working order. However the problem is still there . When we running diagnostics and watching live data it shows fuel pressure is just under 200 kilo Pascal's but the target is 40 to 41 mega Pascal's . Engine starts every time and does not stall but sounds like it starving of fuel when running.what do you guys think is it the high pressure fuel pump , leaking injectior or injectors , possible carbon build up, bad fuel regulator sensor or something else ? Car has 80k miles or so so on the clock.

 

Was the pump and filters dirty? If so, abrasion can open rotor vane clearances and low pressure pump will wear and not make full pressure. I'd start by looking up the LPFP pressure, and then test it were it meets the HPFP. I'm guessing it should have 60+ PSI (420kp). Next look under the car and make sure road debris has not been kicked up and smashed a line flat causing fuel flow, volume issues.

Also, if you reset the code and then keep the RPM's low on drive slowly increasing them, you might get to see that it only runs lean under load, meaning its volume issue and less of a pressure issue. Look at the OBD Freeze Frame Data to see when the code appears, i.e., what conditions the engine is at.

Your user name, any chance you're on Yamaha motorcycle forum?
GL

 

Hi thank you for your reply , the pump and the filter in the tank was little bit dirty but not alot . We measured the pressure by connecting barometer on the fuel line just before the high pressure fuel pump and it have 2 bar pressure which meets the criteria which is 1.5 bar min I believe. Luckily I have another fully running is250 2007 so we will be swap testing in few days to rule out possible part failure one by one plan is to start with the high pressure fuel pump then possibly the pressure regulator sensor ( incase it tells the hpfp wrong signals ) I've spoken to service guys at lexus dealer and they thinking it is likely that there is leaking injectior which won't allow pressure to build . Kaza in Yamaha forum must be different bloke as it is not me .

 

If you pulled the spark plugs, a leaking injector would be obvious, as would the long term fuel trims and O2 readings for the bank leaking. I find this all very unlikely as you'd have other codes. For the most part, the sensors are a go/no-go sensor. Most work until they completely fail and throw the car into limp mode. That said, it is possible the sensor is playing a role.

Again, clear the codes and get the Freeze Frame data, it could be a volume issue. That said, I would simply start with a new LPFP and leave the other car alone, but that's just me. If you disassemble the pump, the DC motor is cheap and plentiful. If you buy a new assembly, it could cost you an arm four legs from Lexus.

Had to check user name. It can be a small world at times.

 

FWIW - plenty of these cars have over 250,000 miles and have not reported HPFP failures so, given the need for many new washers, O-rings, and all of that, I would start on the low pressure side if it were mine. As you just don't know that it is NOT a low Volume condition causing this. Which would likely show up at higher engine loads, in higher gears and while mashing on the throttle. Hence, the freeze frame data telling you when it happens. For that matter, monitor the 2007 from cold start tracking the Engine Calculated Load and HPFP #, then do the same on the newer car. It should give you useful information about how the failing machine should be running.

 

Hey, yea probably will be trying your options first as I'm not really keen on disturbing the other car as it's running good. One thing I think what might be a factor in this that when I bought the car the air intake tube connection to the throttle body was left loose by garage mechanic , car ran fine until now . Lesson here is always check under the hood after taking car back from mechanic

 

^This is why no one touches my cars but me if I can help it! LOL!

Keep us updated. I'd be curious on where/how one would check the HPFP on our motors. Definitely sounds like a fuel-delivery issue. But like mentioned, start with the LP-side of things first...like you have been.

 

Wasn't keen to do it but figured out the problem by swapping out parts with my 07 Is . So we swapped out the pump in the tank , the fault was still there so wasn't the low pressure pump, next we swapped over the HPFP and no fault so that was the problem , high pressure fuel pump was broken and wasn't pumping enough . Must of been bad fuel ...

 

Curious, would you be willing to dismantle the bad HPFP and take pics of the internals? Curious to see 1) just what it looks like 2) what could have caused this issue.

Thanks!

 

Ye opened it up and had a look , didn't see any major damage but I did see some dirt inside, and some sort of substance collected on the walls of some inside

 

Had to read up on how mechanical high pressure fuel pumps work, but it could have been a solenoid failure causing the problem. Maybe not so much the pump mech itself. I don't see any points of failure there in your pics. But thanks for the pics!

 

Did you replace the O rings too?

 

Regardless you'd want to replace with fresh o-rings. Used o-rings is a disaster waiting to happen. Especially if they are fuel delivery components. A new set will have the compression needed to form a good seal. Used they will be hardened at higher milage.

 

Methanol can damage them too. In the states it's hard to get fuel without at least 10% added.

 

Got this code for a day, car had the engine code with traction light on and wouldn’t pass 60km/h, figured it was in failsafe mode ….Changed the filter and fuel rail sensor twice and nothing happened. I then changed the fuel pump in the front i think it’s the high pressure fuel pump and that seem to fix the problem, car is running smoother than before