Will not stay running?

Hi,

The first thing I would check for is an engine vacuum leak. Also, make sure there are no restrictions in the catalytic converter.

Here is a link the explains how to locate vacuum leaks:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Also, if you remove the upstream oxygen sensor, that will allow an extra location for the exhaust to exit. If the converter is plugged, this should be enough to make a difference.

Take a look through this link and let me know if anything mirrors what you experience:

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

One last thought. If possible, record what it is doing and upload it for me to hear. Hopefully, that will helps. And if you haven't checked for diagnostic trouble codes, do that as well.

Take care and let me know what you find.

Joe

I am getting this code but I have replaced all my EGR sensors, so I guess now I need to replace the wiring. I’m going to look at the vacuum leak portion first.

Hello, I'm Danny.

Here is the information relating to your code P0453 Fuel Tank Pressure Sensor Malfunction. Here is a tutorial on how to test electrical wiring:

https://www.2carpros.com/articles/how-to-check-wiring

I've attached a picture step diagnostic flow chart below for your Mazda truck. Let us know what you find and we'll go from there. Hope this helps and thanks for using 2CarPros.

Here are some videos:

Another does the B4000 have a fuel regulator or does it have a Fuel Tank Pressure Sensor? I get mixed answers when trying to shop this part.

Hello again.

Yes, your truck has both a fuel pressure regulator and fuel tank pressure sensor. The fuel pressure regulator is incorporated into the in-tank fuel pump assembly. The fuel tank pressure sensor is mounted in the top of the fuel tank. I've attached pictures below on the location of the fuel pressure regulator circled in red and steps on how to replace the fuel tank pressure sensor. You will have to remove the fuel tank to gain access. If you like I can attach instructions on how to remove and replace the fuel tank. Hope this helps and thanks again for using 2CarPros.

Danny-

I can remove my truck bed like I’ve done in the past right instead of removing the tank right?

This is the correct FTP right?

Hello again.

Yes, if you choose to remove the bed and do it that way the sensor as I stated is on the top of the tank. Yes, that is the correct sensor. Keep us updated and let us know if you have any further questions on this issue. Hope this helps and thanks again for using 2CarPros.

Danny-

I bought a new FTP Sensor. I’ll let you know how it goes.

Hello again.

Sounds good. Thanks again for using 2CarPros.

Danny-

You guys are always a big help.

The new FTP Sensor did not fix my problem. I have been wonder what it could be?

Hi,

If the vehicle is still doing the same thing, have you gone through the FTP sensor diagnostics that Danny provided above? The problem may not be the sensor, but rather a wiring issue or even the PCM.

Is it possible for you to record what it does in the engine area and upload it for us to hear?

Let us know.

Joe

Here you go:

Hi,

Thanks... Believe it or not, that helps. When I listen to it stalling, the idle drops until it finally just stalls. I have a feeling we either have low fuel pressure or a big vacuum issue.

Have you confirmed fuel pressure? Also, have you checked the EGR to see if it holds a vacuum? Have you removed the EGR to see if it responds to vacuum?

If you remove the fuel cap from the filler tube, does that chance anything?

One thing I noticed, and correct me if I'm wrong, it takes two tries for it to run for any length of time. That is what is leading me to think low fuel pressure or fuel pressure drop off.

Let me know if you have done these things. Keep in mind, a stuck EGR or one that doesn't hold a vacuum can be causing this as well. However, by pressing the throttle, you should be able to keep it running. That takes me back to the fuel pressure possibility. Here is a link that shows in general how to test pressure:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

If you look below at the attachment, it provides the pressure/drop-off diagnostics specific to this vehicle. The directions indicate the use of a scan tool.

Let me know.

Joe

I replaced the EGR valve and all the sensors that are linked to it a few weeks ago so I am assuming it has nothing to do with that. however, it started the same with the gas cap on vs off. No codes are showing now on my OBD2. But maybe it fuel pressure. I’ll need to test the pressure, what should the pressure be at?

Hi,

I attached the manufacturer's specs for fuel pressure below. When testing, make sure to check drop-off. When the key is turned off, the system shouldn't lose more than 5 PSI in the first minute.

Let me know what you find.

Joe

Do you guys see anything here that would be causing my truck to stall out by itself or when I press the gas? I think this obd2 shows fuel pressure.

Hi,

It won't identify fuel pressure. However, it does provide fuel trims. I saw them for a second but you moved and I couldn't see them again. I think it was around 18%. That indicates the computer is trying to add fuel to the mixture. Can you tell me what the short-term fuel trims are?

Joe

15 and 20.

Also I noticed the o2 reading didn’t look right either.

Here are the o2 readings:

The trims indicate the computer is adding fuel to the mixture, which usually will indicate a lean fuel mixture due to a vacuum leak or low fuel pressure.

However, the one O2 sensor appears normal, and the one doesn't. The Heated O2 sensor that shows 0v is either bad, has a poor connection, or has an open circuit.

I attached a pic below to help you locate the sensor. Inspect the wiring and connection to it. Additionally, here is a link that explains how to test an O2 sensor to confirm if it is the sensor or a different issue.

https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor

Let me know what you find.

Take care,

Joe

See pic below.

You know the MAF reads 0.03 I’m assuming that can cause a stall and or lean mix. I just hope I get it fixed.

Hi,

A MAP sensor should produce between .30 a bd .60 at idle. If you increase the RPMs, it should be between 1.5v and 3.0v. Did you check it that way? Did it respond? Also, the reading you have tells the computer very little to no airflow is occurring. That could be the cause.

What you indicated could be the result of a dirty sensor. Here is a link that explains how to service one:

https://www.2carpros.com/articles/mass-air-flow-service

I would try that to see if it makes a difference. The signal voltage is too low.

Let me know.

Joe

I cleaned the MAF sensor and nothing. also when I crank the truck and give it gas it stalls immediately. Or if I let it sit on idol it stalls within a few seconds.

I may need to buy a new sensor.

With the reading you mentioned, either the sensor is bad or there is a wiring issue. Have you checked connections at the PCM?

I have replaced the PCM also checked all the cables nothing seems a miss. I’ll try changing the MAF Sensor and see. I’ll change the fuel pump the fuel filter check the fuses and kind of lost right now. Maybe I’ll go get a gas gauge and check that fuel pressure.

Wouldn’t my OBD2 show me codes if my MAF sensor is bad?

Hello again.

Before throwing more parts at your truck can you verify the fuel pressure for us? If you don't have access to a fuel pressure tester most auto parts stores like AutoZone have tool loaner programs and can rent you one. Here is a tutorial showing how to test fuel pressure:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Keep us updated and we'll go from there. The fuel pressure specification is attached below. Hope this helps and thanks again for using 2CarPros.

Danny-

Will this work?

Hello again.

Yes, just attached to the Schrader valve on the fuel rail and check the pressure. Keep us updated. Thanks again for using 2CarPros.

Danny-

This is the Schrader valve right?

Hello again.

The Shrader valve on the fuel rail is more desirable to use. I've attached a photo below of its location. Hope this helps and thanks again for using 2CarPros.

Danny-

What do you think?

Not even 20 PSI.

I’ll tell you this; I didn’t change the whole pump assembly just the electric pump itself. maybe I need to replace the whole assembly..

Hello again.

It looks like you found the problem. That is terrible fuel pressure. The specification is to be 56-72 PSI. Not even close. Seems like the fuel pressure regulator is not working correctly. That is separate from what you replaced as just the pump. The fuel pressure regulator is replaced when you purchase the whole assembly. Do you need me to send in-tank fuel pump assembly replacement instructions? Let us know and we'll go from there. Thanks again for using 2CarPros.

Danny-