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Discussion Starter · #1 ·
Hello folks!

I figured I'd post photos of a VIDA diagnostic run showing the pressure values of my failing fuel pressure sensor just in case anyone else may find themselves wondering if their pressure sensor is on the fritz, and have the ability to see with VIDA/DiCE. I also ran a diagnostic test with the new sensor and have that here for comparison (N.B., the y-axis on the graphs aren't the same, so they are awkward to compare side-by-side).

It's always tough to get the car to act up when you are watching, but I finally captured the 'spike' in fuel pressure, where it jumps to 999kpa (~470kpa seems to be normal for my car). Obviously the pressure can't be this high in the fuel rail, so I took it as proof of a failing sensor. Looking at the images, you'll see that the spike in pressure causes the fuel pump duty cycle to drop by ~15% (normal values seem to be around the 45% for my car, and when the pressure spikes, the duty cycle drops to ~30%) , which corresponds to the characteristic surging in power I felt and described in this post: [/FONT][/COLOR][URL]https://forums....-cut-out-at-highway-speed&highlight=fuel+pump[/URL].
Interestingly, the RPM isn't affected in these cases, and stays constant while the pressure sensor sends incorrect data to the pump controller. Perhaps because the torque converter is still moving fast enough to keep everything at the same RPM for the split second the fuel pump duty cycle drops???

Has anyone else ran a live diagnostic test of fuel pressure and fuel pump duty cycle? I'm assuming my car is now operating with normal values, but don't have anything to compare it to...

It's a relatively easy job to replace the sensor. FCP Euro sells them for $51 CAD (39 USD) with lifetime warranty no matter who installs it, while the closest dealer was going to charge me $169 CAD for just the sensor and 1 year warranty, and lifetime warranty if they installed it...for another $170! It pays to shop around.

In terms of the switch, the toughest part is accessing the torx bolt on the rear of the sensor, located on the end of the fuel rail. I disconnected some of the wiring harness from the top of the engine to give me some room to get my torx allen key in there. I didn't have a ratchet small enough to be able to get into this space, so the Allen key was my solution. It's not as efficient as a ratchet, but it got the job done.

After switching it out, it fired right up, and seems to be way spunkier than before! I'm also wondering if my fuel economy will improve after the change...it seemed like the last few weeks I could watch my fuel gauge drop. A guy can only hope!

Now the images:


Pressure_spike1.jpg
Pressure_spike2.jpg
Pressure_spike3.jpg
NEW_PRESSURE_SENSOR.jpg
 

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This is AWESOME - thanks so much.

Since I had the escapade with my pressure sensor, and now I see so many others having the same issue, I think they should be considered to be a necessary replacement. If you have a sensor that's say 8+ years old and you have ANY driveability or starting issues at all, you should just replace this sensor and take the possibility of it malfunctioning out of the equation. It's pretty cheap an pretty easy to change and it's going to fail anyway sooner or later haha.
 

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This is really interesting and relevant to the issues I've had over the past several months. Thanks for posting!

I logged these pressures with VIDA when I was troubleshooting my pump, and I know my pump had the check valve issue because of the way pressure dropped after shutting off the car, but I am now going to go back and log it idle like this too just to be sure the sensor is not causing any shenanigans.
 

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Here's my logs showing how the rail/fuel pressure would immediately plummet when shutting off the car. The low points are when the car is off. Hit the brake, prime the pump, get a surge, crank it up, idle for a bit, then shut off, rinse and repeat.

Now to go back and log it at idle for a while. :)

 

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Discussion Starter · #5 ·
You're welcome! I figured it would be nice to help out others who may be having similar issues...and it gave me an excuse to play with VIDA! It's astounding how detailed that software is!

I completely agree with your assessment, better to replace it than stop moving in traffic like I did. Luckily enough I was on a highway and could easily pull over to the shoulder. A failing sensor gives you enough time to get it taken care of, before a catastrophic failure where the car stalls and won't start again, hopefully not in stop and start traffic where there is a risk of being rear ended. Given that my local dealer stocks these sensors for my car, suggests it's quite a common issue like you mention jadnhm.
 
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