Fuel Pressure Drops, Car stalls

SlyFox1014

SlyFox1014

Greenie N00B Member
Vehicle Information.
2007 Mazdaspeed 3
169,XXX miles
Injen CAI
Turbosmart Kompact BOV
Corksport Racepipe
eBay "cat" back exhaust
Cobb Accessport with Stage 1+ OTS map

Car started and ran fine, had the second cat removed as I was replacing it with the racepipe and it was sitting in my shops parking lot while we waited. Car went in and had the valve cover gasket replaced with an OEM one, LT cv axle was replaced and the racepipe was installed. Now when the car starts it idles for about 5 seconds and dies. This was not an issue before these couple things were done. I bypasses the fuel pump resistor and no change. I have a new MAF sensor and connector pigtail coming just to cover that base but I am leaning towards the HPFP just going bad as a coincidence.
Looking for affirmation or if I should check anything else before replacing the pump.
ITFP holds pressure at 71psi with KOEO, we put a smoke machine on it to mkae sure we didn't have a vacuum leak and nothing.

upload_2023-12-22_11-9-43.jpeg
 
What brand of MAF sensor did you use?

Do you have HPFP internals in the car?

I believe the car will actually idle off of just in tank pump pressure. @Enki correct me if I'm wrong on that one. It does look like your HPFP is functioning though.

Also pretty much everyone here will tell you not to use COBB OTS tunes.
 
You are correct. It will be harder to start without HPFP, but once it's running, you can generally disconnect the spill valve (which will effectively drop to ITFP pressure) and it should still run. Also your fuel pressure max and min in the graph looks normal, so that's not the issue; I would wager it's either O2 or MAF related.

Try disconnecting the MAF sensor and see if it continues to run after starting.
 
I don’t know if it has internals or current MAF as I just recently purchased the vehicle as a project. I believe the HPFP or internals may of been done as there is a zip tie on the high pressure fuel line. If I unplug the MAF runs a little rougher while it does run but dies at about the same time as usual.
 
Please use the Accessport to log every available PID during a cold start (start the log at KOEO), then post that log here.

I'll have a look when I get back from running errands in an hour or two.
 
Here is some data on the MAF and O2 when I started it and it ran till it died. The O2 mA had no change the entire time but the volts spiked right when it died. It looks like the MAF is working as it should?IMG_5441.jpg IMG_5440.jpg
 
Update: I swapped fuel pump relays and no change, we put a relay bypass on and it fixed the issue. Starts runs idles. Any known issues with the relay wiring?
 
Fuel pressure was def falling off in a way that looks like the HPFP isn't being fed. Not sure what the issue is with the relay.
 
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