Fuel pressure drops then stalls

Resolved. See post #59
Updating details: Parts replaced:
HPFP
valve cover gaskets
In tank fuel pump assembly
Fuel pump resistor
Relief valve
All the blue resistors (ETV, Injectors, FP, Circuit)

On to the details...
Gen1, 2007, 224k miles
Turbo is 164k miles old, most everything else is original
Mods: cpe turbo back exhaust with cat, cs tip and sri, cpe pump (previously autotech internals)... I think thats it...

Driving to work one day, car stalled out about 1.5 miles away so barely warmed up. Got it towed home, hooked up AP and watched the fuel pressure to see it was too low to keep it running more than a minute or so. I thought I loosened a wire when I did the oil change and add contact jelly to the starter wire for the clutch pedal sensor. Found nothing there but who knows. So, since HPFP was making lots of noise, we replaced it with a known working cp-e pump. Pressure was better but still died. Old pump was definitely shit as you could feel it when you pushed it in by hand. Wasn't smooth at all. Did the in tank assembly and it was now better again, but still not hitting 1k. Did the resistor, slight improvement. Relief valve was shot as i could blow a little air through it. Changed it and BAM - great fuel pressure. Perfect in fact but car still died after a minute. Replaced all the blue relays and it ran for damn near 15 minutes until coolant temps hit 138. Up til then, desired HPFP psi was just about dead on. Car never sounded as good as it did. Misfires I previously had for over a year were gone it seemed. No CEL for P0300 or any codes showing on the ap throughout any of this but keep in mind, battery was disconnected several times so who knows. During warm up, I rev'd it up and she sounded awesome. Then the fuel pressure drops and it stalls out.

Gasket on the valve cover was replaced since the old one leaked everywhere. Oil was in the plugs, which I cleaned up and regapped prior to putting it all back together. Even put contact jelly on both ends of the coil pack springs.

Reflashed maps - didn't help

I've hit a wall here. It's frustrating to no end. I want my car back. Any help will be greatly appreciated.

 

Any codes? What is your KOEO fuel pressure? When the engine does idle, what is your fuel rail pressure?

 

No codes but that is likely due to the battery being disconnected so frequently. KOEO, sits around the 65 mark. Cold, got up to 1600 briefly. Drops down from there.

 

Well if your KOEO pressure holds 65 psi, then your relay and wiring are likely good and is sending the correct voltage to the In-tank pump. You can bypass the Pump resistor by jumpering the resistor connector. Just unplug it from the resistor and jumper the two female tabs together with a wire or paper clip. This will send 12 volts to the intank pump all the time. I'm leaning more towards a pressure relief valve problem or spill valve being stuck. Do you have a power probe?

 

Have you checked your release valve on the hpfp?

crapatalk it sucks for free

 

Replaced the HPFP

 

The whole pump or just the internals?

crapatalk it sucks for free

 

WHole unit. Went from an upgraded pump (don't recall which internals) to a slightly used cp-e pump.

 

Have you checked the electrical on the release valve?

crapatalk it sucks for free

 

Generally if you have a hard fault with an electrical issue, (short to ground, short to power, or unplugged connector) you will get a CEL almost immediately. The relief valve failure can cause your issue if the ball inside is not sealing and not letting the pressure build at all. Can you keep the motor running if you lightly press on the gas pedal after it starts? Have you tried swapping the fuel pump relays with the others in the engine bay fuse panel? There are 2 other relays in there that are the same type

 

If I short one of the relays, I can maintain enough pressure to keep running but thats it. Keeping my foot on the gas only proves to kill the engine. I juts pulled the relief valve and I am able to blow air in either direction. Not a lot but I still get a little through.

No. Explain please.

 

https://corksport.com/blog/hpfp-troubleshooting/

http://www.mazdaspeedforums.org/forum/f111/how-replace-relief-valve-rv-95418/index2.html

If you can blow through the release valve it's dead.

crapatalk it sucks for free

 

Wow, they had a hard time getting it off. I got the clip with a small needle nose and the valve itself with a regular wrench. Not a lot of room with the hardli e in front but it broke loose in about a 1/8th turn. Did the rest by hand. It's on order so let's see what it does.

 

Is the fuel pump resistor plugged in? It looks like an HID ballast and is mounted on the driver side frame rail. If it's bad or not plugged in, it will do exactly what your car is doing.
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Brand new one installed in all this. Old one gave zero resistance.

 

Yeah if you can blow through the relief valve I would start with that.

 

Ok, relief valve installed and I get full fuel pressure again. It ran great for a whole minute before it died again. I tried jumping the fuel pump relay slot again and with that, I get full desired hpfp psi. I'm at a loss here.

 

Disconect the Yellowish clip off the fuel pump and hook a hose to the fuel inlet Y on the fuel pump. Put the other end of the hose into a bucket. Bypass the relay, check flow. Make sure to check both circuits, there is a KOEO to prime the pump and another curcuit for continuous opperation once the engine is started. Sounds to me like your In tank fuel pump is not supplying enough fuel to feed you thirsty engine.

 

I thought about the itfp so I replaced it along with the entire itfp assembly.

 

I don’t want to know how much money you threw at this problem. Lol

Unplug you MAF and give it another go. (Force your Car into closed loop) see if it’s boost leak related.

It’s got to be something simple, like a loose ground or something. Especially if it runs and dies.


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