lottathought

Hello all,
I am trying to diagnose an issue on the wife's 2010 RX350.
It is the base model 2WD. It has 211K miles on it.

And I will say now...for anybody that wants to say that Google is my friend...no it is not...at least not in this case.
I have Googled. I have searched on this forum...and I have scoured over pages and pages of troubleshooting questions. None seem to apply exactly.

So...moving on to the problem..
It has gotten difficult to start. When I say that it has gotten difficult to start, I mean it will turn over and turn over. I hit the start button and it will turn over without starting ..until I hit the start button again to stop it.... and...maybe the next time that I try, it may start right up. Or..it may do this a couple or so times and then start.

I have pulled the codes. There are no codes that seem to deal with this issue.
I have tried some tests...
I will turn the car on...not starting it...let it sit on for 30 seconds and it usually starts right up. This is when starting cold.
Now I know what you are thinking...Fuel pressure regulator.
You are probably thinking that the regulator is going bad and the pump is having to build up pressure to start.

I originally thought that too. But...if it were the regulator, I would expect that if I had the car running, turned it off and waited 30 seconds, it should again crank right up. The regulator has not had enough time to lose pressure...and if it were losing it that fast, then I would not expect the pump could ever build it back up.
What I am finding is that it can be very hard to restart in this scenario...often taking multiple attempts.

As far as driving the car...there may be a slight loss in acceleration. My wife says that she thinks it might be...but it is slight enough that she says it might be her imagination.
For this reason and that the test seems to eliminate it as the cause, I am hesitant to blame the pump.
I have run a good fuel system cleaner through. if anything, the issue got worse. It did not get better.

So now I am considering the sensors. Maybe the sensor is not turning on the pump like it should?
But then it comes to which sensor. The Fuel Tank Pressure Sensor or the Fuel Rail Pressure sensor?
The problem here is that I can only find a passing nod of info on either. And this is even when I expand to go beyond my year and even beyond an RX350. (I have looked at other other years of the RX350, other Lexus cars and even looked at a similar year Rav4) The subject of which sensor to look at first never comes up. I get a vague reference on where to look for these sensors and no real info on what to troubleshoot in them.

For anybody that wants to suggest the battery or starter..that seems unlikely.
The car is not slow to turn over. It is strongly doing so. it is just not cranking up when it does.

I am not a newb under the hood...but I am far away from an expert.
However, with decent direction, I can usually get by.

So what am I missing, if anything? Do the sensors make sense? If so, which one and where is it? And what troubleshooting steps should I take?

Thanks in advance.

chuyrobles

I am thinking a bad crankshaft position sensor, but that usually causes the CEL to light up. Next up, probably check the plug coil connections and wiring for cracks; there could be some grounding going on. Also, a bad ignition/fuel relay may be sticking.

lottathought

Thank You. I will check these out

CaptStumpy

fuel, air, spark, timing

Assume air intake and exhaust are not clogged, and there is good spark, and timing is OK..
Start with reading the fuel pressure. An intermittent pump, clogged fuel filter, or bad injector is usually the cause of a hard start condition.

afpj

When you say there are no codes that seem to relate, are you saying there are no codes at all? Seemingly unrelated codes could be relevant, such as evap type codes. What are your fuel trims? Do you have a bidirectional scan tool?