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Until some one opens one up we will not truely know.
I don't think that's necessary. It doesn't always have to be an episode of 'sliced'...although I did enjoy that show thoroughly. ?I did some digging into how "Pressure Transducers"operate. Here is what I found:

https://www.teesing.com/files/downl...ide-to-understanding-pressure-transducers.pdf

I knew there was something different just from the eyeball test, so I started reading into the different types of sensor and how they work. Basically, the old sensor is a "sealed" sensor. It does not use an atmospheric reference point, as the new gauge does...indicated by the hole on the side.

35820



The "old" gauge seems to be what is called an "absolute pressure" gauge, meaning that it is measuring lowside fuel pressure, referenced ONLY to its sealed, vacuum housing. The new gauge is either a "differential pressure gauge", or, more likely, a "gauge pressure" gauge. (Their terms, not mine...and you can read more about each in the link). The problem with "absolute pressure" types of gauges is, and I quote:

"The major drawback is the trapped volume of air is sealed in and becomes is sensitive to temperature changes; both ambient and pressure media. When sealing a volume of air in a chamber the “Ideal Gas Law” presents challenges that are unavoidable. When talking about the ideal gas law as it pertains to a sealed gauge pressure transducer, the trapped volume of air expands or contracts with temperature changes and has a direct effect on the force applied on the backside of the diaphragm. The initial force on the back side of the diaphragm increases or decreases based on the direction of the temperature change. The lower the pressure range the greater the impact it has on the sensors overall accuracy "


So the "reference port" is ABSOLUTELY INDICATIVE that the old lowside fuel pressure sensor is not working in the same manner as the new one.
 

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So the "reference port" is ABSOLUTELY INDICATIVE that the old lowside fuel pressure sensor is not working in the same manner as the new one.
Pretty bold statement to make without cutting open both the BA and CA sensors and actually seeing what the construction is.

Granted your generic figure of a pressure sensor had a reference port in the same general location as the hole in the CA sensor. But as previously mentioned it could be a tooling hole, an atmospheric reference or a fill port for the space between the diaphragm and the sensor. Can't know without disecting one. Even if it is an atmospheric reference port we do not know if the BA sensor has a reference or not, it could be getting it's reference through the connector. Doesn't take much, could be as simple as some clearance around the electrical pins.

Even if the BA is sealed it certainly isn't an absolute pressure sensor with the CA being a gauge, that would require ECU programing changes for that to work. Yes the captured pressure would change with temperature as you suggest but it is quite small. Going from 75F to 100F would raise the pressure by 1.3 psi certainly not enough to impact the operation of the engine. Plus in this example that additional pressure would make the ECU think that there is not enough fuel pressure resulting in the fuel pump being driven harder and a richer mixture. The catastrophic failure mechanism with the sensor is the engine goes drastically lean.

This type of sensor typically is going have an accuracy spec in the 1 to 2% range and the sensor itself will change its output over temperature that could also be 1 to 2% of its rated operating temperature range. Assuming a 100 psi pressure range you are talking 4 psi.

I am still not convinced that the CA sensor is anything other than a part made to the same specs by a different supplier.






Dave
 

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But as previously mentioned it could be a tooling hole, an atmospheric reference or a fill port for the space between the diaphragm and the sensor.
Yes. atmospheric reference point. Correct. that's exactly what it is. It's not a tooling hole.
 

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Even if the BA is sealed it certainly isn't an absolute pressure sensor with the CA being a gauge
You are correct here. I was wrong in my initial assumption that the 'old' LFPS was an "absolute gauge". Both gauges are "gauge pressure" gauges. The difference is one is sealed and the other is vented.
What is the difference between Vented and Sealed Gauge Reference Pressure?
Quote:
"Sealed gauge pressure is the best approach for applications with a high pressure range and a consistent temperature."

I've been datalogging my "desired LFPS" and its usually around 78 psi, which seems to be slightly above 'faucet pressure'. I'm not sure if you would consider that a high pressure application. And we can all attest that the engine bay is far from a consistent temperature.
 

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Not trying to be argumentative but until both parts are cut open we do not know anything about the design of this part. My only goal is to get people to think about alternatives to "its a new design".

The fact is;
1. Ford has been using the same fuel pressure sensor in all its gas engines since 2010. It is not unique to the Ecoboost Mustang and you don't here about issues with the same sensor in a GT Mustang.
2. The BA marked part has been in Ecoboost Mustangs since day one and still is.
3. The CA part is only available as a replacement part and the package carries the same part number as the sensor in all Ford gas engines.

Dave
 

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Interesting, there have been mixed reports of some models after mid 18 still having the old sensor, and others saying they were all replaced.
Nothing unusual about that, automakers will always use current stock components until exhausted before incorporating a new component.
 

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@dgc333 Dave also not trying to be argumentative, but why would several of the most reputable pro tuners all recommend swapping out for the new sensor if it's just a part number?

From Tune+
Ecoboost Mustang Fuel Sensor / EVAP Solenoid

The Ecoboost Mustang has received updated lowside fuel pressure sensors and EVAP Purge solenoids over the years. No information provided by Ford, just new part numbers and clear updates to the product. These new parts magically fix known issues with the Ecoboost Mustang.


  • The new lowside fuel pressure sensor cures a High Pressure Fuel problem. When the lowside fuel pressure sensor fails, when you get into load the fuel rail pressure will drop to almost 0. The high pressure fuel pump thinks there is a problem and instead of bypassing it just simply shuts down.
  • The EVAP purge solenoid update cures issues with the short term fuel trims when under load. When the EVAP purge solenoid fails the short term fuel trims will go to 0 and you will not get any fuel corrections under load (mostly full throttle) and the car can potentially go lean. If you have port injection or methanol injection, or making 400whp+ this can cause catastrophic failure.
  • Both items can fail without any check engine light, and you would have no way of knowing. It is best to just replace both of them to avoid any issues, they are extremely cheap.
 

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Nothing unusual about that, automakers will always use current stock components until exhausted before incorporating a new component.
The CA part has been around since 2016 (if not earlier) when the internet histeria to swap out the sensor started. Ford consumes some where on the order of a million of them a year considering all the vehicles that get the same sensor. Here we are in 2020 and Ford is still using the same BA part. If it was a matter of consuming old stock that means they would have had to have 4 million or so sitting on the shelf. Companies interested in making money do not keep years worth of inventory on the shelf.

It certainly is not a current stock thing.

Dave
 

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@dgc333 Dave also not trying to be argumentative, but why would several of the most reputable pro tuners all recommend swapping out for the new sensor if it's just a part number?
Well no one has shown any evidence that the sensor marked with a CA is anything other than a different supplier that made the part with some inconsequential visual differences. The part number has not changed, it has always been BU5Z-9F972-B and still is for the Ecoboost Mustang. Some of the packaging i have seen pictures of posted and what i have seen poking around in the Ford parts catalog it says the BU5Z-9F972-B superceeds
the BU5Z-9F972-A sensor but that was around 2010. This would suggest that if there was a new design the part number would change. To me the actual parts being marked with different numbers is something other than a part number.

The fact that Ford has not issued a TSB or a recall for the sensor would suggest that they don't feel that there is an abnormal failure rate and that is further supported by the fact they are still using the same BA part. Also, you don't see complaints about this same sensor on the F150 forums or other Mustang forums in relation to the GT.

When Tune+ first reported a low side fuel pressure sensor failure in 2016 he described what happened and what to watch for to determine if your sensor was failing but there was no mention of just replacing it if there were no symptoms. Why he has changed his stand i have no idea.


Dave
 

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Discussion Starter · #54 · (Edited)
Dispite al those rumors of some batch of the "old" (BA) sensor has issues or NOT and whe don't know much about the "new" (CA) sensor say some people who switch the sensors that al the problems they have observed disappeared en the cars now better performs.
Is that no reason enough to swap a sensor from $40 and take the risk to blow up your engine!
 

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Best money I spent! My 2018 equipped with the "BA" failed to the point where the car would barely run. Before the failure I had an inconsistent problem with idle dipping which I could never seem to track down. Replacement with the CA not only got the car running like new again, but the idle dipping problem went away. I believe the sensor was failing for a while hence the idle symptom before complete failure. No more problems so far since replacement with the CA. Could I have replaced with another BA? Sure, but why take the risk when for the price of a tank of gas I can have peace of mind. Granted I was going to replace it before the failure ever happened and I already had the new part on hand (luckily), but had never gotten around to it. Teach me to be lazy!
 

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Discussion Starter · #56 ·
Best money I spent! My 2018 equipped with the "BA" failed to the point where the car would barely run. Before the failure I had an inconsistent problem with idle dipping which I could never seem to track down. Replacement with the CA not only got the car running like new again, but the idle dipping problem went away. I believe the sensor was failing for a while hence the idle symptom before complete failure. No more problems so far since replacement with the CA. Could I have replaced with another BA? Sure, but why take the risk when for the price of a tank of gas I can have peace of mind. Granted I was going to replace it before the failure ever happened and I already had the new part on hand (luckily), but had never gotten around to it. Teach me to be lazy!
Better late then never !
 

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By all means if you have symptoms the sensor should be replaced even if it is a house brand from your local NAPA.

My only point has been that there is no evidence that the replacement part marked CA from Motorcraft is any different than the part that came from the factory or that there is any design flaw in the part the factory has been installing.

Dave
 

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Again this doesn't prove either point, but take it subjectively. I emailed my tuner, Ryan at PD tuning just to get his opinion on the matter and his experience with the new sensor.

From Ryan:
I haven’t seen a CA sensor fail yet. Doesn’t mean they won’t I’ve seen plenty of BA sensor’s fail. Doesn’t mean the CA sensor’s won’t fail I just haven’t run into it yet.



Respectfully,

Ryan Martin

Again this isn't proof of anything, but from someone who daily works on and pushes the platform.
 

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