Fuel rail pressure sensor reading 0 volts at all times.

Did you unplug it while the car was running? Unplug it them turn the car on. It should run.

 

I said all this in shout but I am going to say it again here.

1. Check the ECU with a multimeter to make sure you are seeing actual voltage of the fuel rail pressure sensor. There is no way the ECU would know fuel pressure if it is reading 0v as fuel pressure is simply a calculation based on voltage. https://manualzz.com/doc/25080746/2007-mazdaspeed3-ecu-connector-pinout PIN
   1. 2I - Green/Black -Fuel Pressure sensor reference voltage
      
      
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2. Check you purge valve or just block it off temporarily, see if that helps.
3. Make a list on the first post of all the things you have done and results so we can keep up.

 

Hey Johnny,

This is probably a dumb question, but how do you use the multimeter to check the voltage at the ECU...just curious where you stick the pins for connectivity.

In the back of the wiring harness or through the insulation of the wire?

I know it's a dumb question, but I've never had the misfortune to check for electrical gremlins *knock-on-wood*

 

You should be able to do it like this, just don't get too crazy and jab it in there super far, If you have a paper clip or something you could do that too. You can also get a multimeter with sharper needle like probes that can go through a wire jacket without messing it up.

 

That's awesome...thank you for the picture and explanation!

 

I would recommend you watch a few videos like this so you don't fry something.

 

Interesting development. I havent had time to do anything with the car because i went to school and went straight to work and worked till 1am and then woke up went to school and now i have to go back to work in 2 hours after i get my kids taken care of. But i did try and see if it would run without the maf and it took a couple tryes but on the 3rd try it went to die and caught itself and it started running and i noticed it runs almost exactly the same with the maf unplugged as it does with the maf plugged in.. does this mean possibly my maf is bad? And could one of ylu fellas do me a favor and set your AP to monifor HPFP Sens voltage and tell me if it showes you any other value besides 0 next time you drive your car today? Im just so busy and would be grateful if you could save me from having to probe my ecu harness

 

If the behavior didn't change with the maf unplugged then it's not the maf.

 

Oh okay. It does change when i unplug the O2 sensor idk if that makes a difference here are pictures of the engine bay

 

Original post is updated with things i have done and results.

 

Dude just test the wires between the HPFP and the ECU. I don't know why that's such a hard issues it's like a 5 minute test. They're literally on the of the engine.

 

Okay ill do that tomorrow morning. Im at work till 3am tonight

 

Why are you suggesting to test the hpfp wires? What am i looking for? My AP is showing fuel pressure

 

Fuel pressure is read by the fuel pressure sensor on the fuel rail. Not the Spill Valve. You are saying that the HPFP shows 0 volts but aren't actually verifying that the wiring between the HPFP (Spill Valve) and the ECU are good.

 

Im sorry if i caused confusion with my choice of words. Set the AP to monitor “HPFP sensor voltage” it shows 0 volts. Does this mean voltage to the fuel rail sensor or is this referring to the spill valve voltage? I may be misunderstanding that.

 

It means the the voltage to the Spill Valve

 

Oh wow. Okay well that makes alot more sense then. Ill check that voltage in the AM. Now if there really is 0 volts going to it would that be a relay failure or spill valve failure?

 

You want to disconnect the connector at the spill valve and the connectors at the ECU. Measure the resistance for the wires at the spill valve to the right wires at the ECU connector. You should have less than 2 ohms on each wire. But that doesn't necessarily mean each wire is good, because you could have one single strand of wire that's ok and the meter read low resistance. Or on the other hand if you check resistance between the ECU and the spill valve and there is no resistance/continuity that means the circuit is open, a broken wire or too much resistance. Your meter would read something like OL or just ---

Think of electricity like water, with wires being a garden hose. Instead imagine though that instead of one hose that inside the hose are a bunch of straws for the water to flow through. At the end of the hose is a water wheel. Normally if all the straws inside the hose are good and all the water can flow through to the end it can spin the water wheel. Now imagine it as only one straw in the hose is good and only a small amount of water (electrons) can flow. Water will reach the wheel but won't be enough to turn the wheel.

That's how high resistance works. Each strand of wire is like a straw for electrons to flow in a circuit. The speed at which the water (electrons) flow is amperage, the amount of water available is your voltage. Any kink (resistance) in the hose (wire) makes it harder for the water to pass through

So once you verify that there is low resistance between the ECU and the spill valve, you need to check voltage level at the spill valve. You'll reconnect the ECU, turn the key on and at the Spill Valve connector set your multimeter to DC voltage and check what it's reading.

You should have battery voltage there unless I'm wrong because I don't think the spill valve runs off a 5v reference. If someone can confirm this please chime in

If you have voltage at the valve, low resistance in the wires, and the ECU isn't seeing voltage from the spill valve it could be a few things

A bad spill valve
A bad ECU
Bad wires where not enough current can pass through

You can verify the current issue but until I know you can do these first tests correct I won't tell you so you don't mess anything up cause of you do it wrong you can fry components.

 

Here is the entire ecu pinout for first gen if its not already on here

 

Okay i did the tests. The wires show 0 resistance.

I set the multimeter to read 400 ohms and when i touch to both ends it will show .003 and fall to 0

koeo one wire shows 11.81v the other wire i assume is a ground shows 0 volts. This is using the ground that is connected to the chassis

when measuring resistance accross the spill valve itself it shows 1.5-1.6 ohms.