Fuel rail pressure sensor reading 0 volts at all times.

Anyone know why my fuel rail pressure sensor would be reading 0 volts at all times? Im about to tear it appart and see if something is wrong today just wondering if this is abnormal because everything i read says the voltage should vary.

I was having some problems with high positive fuel trims and a cylinder 3 misfire when this started but concluded that when i had the car tuned the OCC hose was kinked and not allowing flow from the crank case to the intake manifold and was not getting the air from the crank case accounted for in the tune. the car is adding fuel at idle still the LTFT sits around +7-9 depending on ambient temp but i hear an occasional afterfire and it will spit some raw fuel out the back IE: black soot
Edit: the car now runs worse than mentioned above and STFT bounces between 20-24 and the car is misfiring much worse and spitting black soot from the exhaust randomly in little pops

Things i have done as of 12/2/2021

• I checked the spark plugs and none of them look like theyre too rich
• I have boost leak tested the car and found 3 small leaks but when fixed they made no difference in the way it runs.
• i have changed the plug in cyl 3 with 3 other plugs
• i have swapped the coil with another cylinder and still it persists on cyl 3.
• ive checked the whole intake tract multiple times, including the manifold and throttle body gaskets and everything is sealed up.
• I have changed the injector from cylinder 2 to cylinder 3 and visa versa to no avail
• I changed the o ring on the MAF to make sure its sealed
• i have cleaned my MAF thoroughly and carefully
• I have checked the MAP sensor to see if the O-ring on it was bad and it is not
• I took the intake manifold off and took the injectors out and #2 came out without the seal so i had to keep putting it back into the seal and slowly worked it out by putting the injector into it and pulling it out with the corksport injector tool
• i cleaned each injector and injector port thoroughly and retorqued them to german torque specs of gutentight but not gorilla fucked tight
• I replaced the fuel rail pressure sensor and after i put all of this back together it runs like absolute shit and is not even driveable (it was drivable before i pulled it apart but would flag a misfire on 3 every 20-80 miles inconsistently)
• Unplugging the MAF makes no difference in the way it runs (but makes it pop more)
• Unplugging the O2 sensor makes it stop popping randomly (sounds like a backfire)
• When my PRV failed a month ago i did clean the spill valve and i spect the HPFP and everything was fine inside
• I did add 2 cans of injector cleaner to the full tank of gas trying to see if this would help (i thought maybe an injector was gummed up)
• I have compression tested the car cyl 1.180/ cyl 2. 155/ cyl 3. 175/ cyl 4. 180 (yes im counting the cylinders starting at the timing chain side of the motor and this comp test was done with the car at operating temp.

Things i plan to do tomorrow 12/3/2021

• Cylinder leakdown test, and in the event these numbers are normal i will continue as follows
• Probe ecu harness to Confirm voltage to fuel rail pressure sensor
• Remove everything down to the intake manifold and injectors and carefully and meticulously reinstall everything with proper factory torque specs
• Replace original pressure sensor i removed that i thought was bad

 

Is your tune completed? If no, stop fucking with things until it is. If your tuner finds problems, he will let you know.

 

Tune has been completed since before the issue arose. Nothing was changed during the tune other than failed parts.

 

Did you just notice this issue or can you guarantee that it just started recently? Is the car running bad in any way? Any CELS?

 

The issue just started suddenly last sunday right before i replaced the turbo. im getting a CEL for a cyl 3 misfire and i can hear little pops at idle like its rich and creating an afterfire when the extra gas hits the exhaust. The wierd thing is the misfire comes at random times. I drove 100+ miles after i cleared it and nothing then it comes on while im idling. Then ill clear it and it will come on after 10 miles. Then again ill clear it to see if something specific makes it misfire and it will come again. After 50 miles. Ive noticed that if i let it idle a while and turn the wheel just to put a tiny bit of load on the engine for 1-2 mins it will come on. But if it dosnt idle for long it dosnt come on. And it almost always comes on at idle.

 

Check your plugs (the gap) and heat range for the fuel you run. High mixes should not run step colder, nor should stock turbo cars really.

 

Im running ngk 6510 gapped to .025 as recommended by the tuner.

 

What fuel?

 

91 oct pump gas from cali

 

I took my intake manifold off to get the pressure sensor out to change it and i noticed there is oil covering the hold down for injector 2 and the wire harness connector for injector 2 as well as the injector connector for #3. It looks like maybe the pcv plate is not sealing and venting crank case pressure onto the block.

 

Did you ever take the injectors out? If so, did you replace with stock or reuse?

 

I took the injectors out to replace the seals with CS injector seals. While they were out i cleaned the tips with injector cleaner to get the carbon off. but that was like 2 tunes ago.

 

Is the rail sensor supposed to be 0 Volts at all times?

 

*Sigh.* Unsubbing.

 

okay i have confirmed that fuel rail pressure sensor reads 0 volts at all times. regardless of throttle pos. im not gonna beat that bush anymore. however my car is running like absolute shit and i am desperate for help. its breaking up super bad STFT are like +20-24 and the exhaust smells like raw fuel. i have no fuel leaks and i boost leak tested the car up to 26psi i did find 2 minor boost leaks and corrected them however that did nothing. so the car is now "air tight" no air leaks so to speak from the turbo inlet all the way to the cylinders. not a sound except the deep hiss of air slowly leaking from the valve cover breather and the pressure drops very slowly idk if this is normal or not so someone please fill me in if not. i did a compression test and the came out as follows. cyl1 180 cyl2 155 cyl3 175 cyl4 180. i know cylinder 2 is low and thats not good but i keep getting a cel for cylinder 3. i swapped the ignition coil, spark plug and even the fuel injector from cylinder 2 over to 3 and visa versa and still cylinder 3 misfire. at idle the AFR is just crazy bouncing all over and will occasionally flash to 15.xx and when it does this its followed by a loud POP like a backfire. i unplugged the O2 sensor to see if it made a difference and it sounds "better" and it drives super sluggish like its too rich but its not doing the popping at idle as i mentioned it does when the o2 is plugged in. idk if this means anything or not but i really need help. i dont know what else to do and i need this car to work so i can go to school and work and i have no money to pay a mechanic because i have 4 kids and its about to be christmas. so please from the bottom of my soul ill take any advice and any clues as to what is happening i just really need help. i took a log driving around the block just cruising easy and a couple times i tried to go into boost to see what it would do and it just breaks up super hard and bucks really bad.

 

So you're daily driver is this MS3? You have 4 kids and you don't have money to pay someone to fix the car?

Sounds like it's part out time or just sell the car, buy a Honda Civic and be able to provide for yourself and your family instead of running in circles over this car like you've done the last few weeks.

A lot of us had given you advice on what to do. If you can't take the advice, follow directions, then all that's on you. If you want advice and a clue of what to do it's put your wants on the back burner for a while till you get your stuff together and either park the car until you can pay someone to fix it or sell it.

 

What happens if you unplug the maf?

 

@Easter Bunny[/USER] if i unplug the maf it dies right away. It wont stay running period. L337 thanks for the life advice.

 

Hey Matt,

I'm not going to be much help, but have you tried cleaning the spill valve on the HPFP? Maybe try cleaning the ground strap next to the HPFP. Also, have you had the injectors cleaned, leak and bench tested? This includes measuring resistance and impedance. The only thing that doesn't seem right is that you've swapped the injectors, plugs and coil packs and the issue remains at cylinder #3, which leads me to my next point.

How many miles does your car have? I think I saw you once say it was at 180,000 miles. With that much, its possible the engine could be worn out.

Have you tried to do a leakdown test on the engine?

I think all L337TurboZ was trying to say is that with 4 kids and school, this car is starting to consume you when you have other priorities. At the end of the day, it's just a car, but it's a device you need to rely on. The speeds can be finicky at times, especially at higher miles.

I wish you all the luck. You've put in a lot of effort with it, so I'm not going to take that away from you. But if it were me, I'd really try to take it to an experienced mechanic to get it looked over. Do you have anyone that could loan you a few bucks to do that? There's no shame in asking for help every once in a while, especially when you have as much on your plate as you do.

 

https://mazdaspeeds.org/index.php?threads/how-to-diagnose-thread.12295/

Check out this thread I made. Use this to give you tips and advice for doing electrical diagnostics.

You need to verify the wires are good between the Spill valve and the ECU, verify there is no corrosion on the ECU connectors and verify there are no shorts in the harness