Hey Y'all on my Edge Evolution (Finally getting my DP for Christmas ) which has a digital monitor for gauges and codes i have a PID "gauge reading" for Barometric pressure. Just curious as to what this reading is actually for. I have had it up on the screen once or twice and have never seen it change. And to be honest that was like 3 years ago as the only 4 PIDS i keep up on the screen are bst psi, EGT, TFT, and RPM.
Just wondering if anyone has any idea about BARO pressure and what it should be reading?

 

Baro is used to help the PCM calculate air mass, which varies based on things like altitude or weather.

 

Right, well living in Florida i don't know what it should be reading. Also what sensor In the truck would give this BARO info to the PCM ?

 

The BARO is built into the PCM and it should read about 14.5 PSI (4.5 - 4.6 V) at your altitude (whatever the reading is, it should match your MAP and EBP +/- 0.2 PSI before starting the engine)

 

My E99 baro sensor was external to the XLE4 PCM. It was under the dash and wired to the PCM.

Along with EOT the BARO pressure is also used to determine on time of the GPR.

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From the Ford service manual:

The 7.3L diesel engine uses a glow plug system that preheats air in the combustion chamber to improve cold engine starting.

The system consists of:

<DIR><DIR>glow plugs.
glow plug relay.
glow plug module ( CA Trucks and Excursions)
powertrain control module (PCM).
engine oil temperature (EOT) sensor.
barometric pressure sensor (BARO sensor).

</DIR></DIR>The glow plug system is electronically controlled by the PCM. If the oil temperature is below 131°F (55°C ) the PCM will energize the glow plugs immediately after the key is placed in the ON position.

Then, depending on the readings from the engine oil temperature (EOT) sensor and the barometric pressure (BARO) sensor, the PCM determines how long the glow plugs will be on.

Glow Plugs — PCM-Controlled

The glow plugs are located in the cylinder heads, under the valve covers.
The glow plugs are self-regulating. If the engine oil temperature is above 131°F (55°C ), the PCM will bulb-check the WAIT TO START lamp but not energize the glow plug relay or control module.
The PCM system uses the glow plug module (if equipped) to conduct current to the left and right bank glow plugs.

The PCM protects the glow plugs by energizing them for short durations if the battery voltage is abnormally high.

The glow plug ON time varies from 0-120 seconds depending on battery voltage, engine oil temperature and barometric pressure.

On California vehicles the glow plug monitor (GPM) system is part of the On-Board Diagnostics II (OBD II) System.

The GPM system is designed to find failed glow plugs or failed wiring in the glow plug system.
A failure in the glow plug system will set a diagnostic trouble code (DTC).
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EDIT: Also there are two manifold air pressure readings when using a scantool.

Absolute Manifold Pressure - Bosst pressure plus baro pressure.

And

Manifold Gauge Pressure - Absolute minus baro pressue, which would equal boost pressure. The PCM subtracts the BARO pressure to determine the gauge pressure.

 

Right on Fellas thanks. I have never looked at it before i start. Like i said only when running down the road. Checked it today on my way to town. Swaped the RPM display for BARO PRESS and it read 15kpa. I had it up for 15 or 20 min and never changed.

Thanks for the info. I just didn't know what it did and wanted to make shure i did and it was working properly.

Speaking of MAP sensors and such. My line running from the spider to the map sensor is looking a bit weak. Think i may replace it for preventive maintenance. What kind of hose do i need?

 

15 kPa only equals 2.175 PSI. Something doesn't jive.
Are you sure that wasn't 15 PSI.

At sea level baro pressure is 14.7 PSI which equals 101.35 kPa

 

Your MAP line sees full boost pressure. If you suspect it, it's not an expensive or difficult thing to replace.

 

Thanks Tug, Ohhhh yea easy quick maintenance but what kind of line do i need to pick up ? What type of hose and for what psi.

 

I never looked into this, I installed an Overboost Code Regulator, which came with the tubing. The MAP line can see boost close to 30 PSI with mods on stock injectors and stock turbo.

 

Yea i figured about 30psi. I will hunt something down this week some time. It is just getting a bit stiff and i just like keeping my odds and ends in check. I will say this, been reading up a lot on different posts and man you shure know ur stuff. Im about to be doing some mods after christmas and more than likely will be posting for ted tips on them. Hope you get time to chime in on them.

Thanks again. and when i find the correct hose i will post what i used.

 

I learned almost everything from reading the documentation, tinkering with wrenches, and getting feedback from the forum. This is my first diesel and I didn't dive in until about 14 months ago. Since it's the internet and everybody has different configurations on their trucks, it's best to get a "chorus" of input... not just one person. I don't even trust me to get it right the first time.