Fueling Gremlins

[AndyW]

So, one a recent track day, car started sputtering and stalling. Logs showed rail pressure dropping as low as 37#.

Typical Log here: https://datazap.me/u/andyw/suspect-h...zoom=1529-1643

LPFP was a Fuel It stage 2 with Walbro 525, replaced last year. EKP was brand new. So I suspected overloading EKP module or HPFP. Swapping in the EKP Bypass cable https://www.seemslegitgarage.com/pro...bypass-harness didn't fix it so I replaced the HPFP. I had also randomly been getting "injector pressure too low" shadow codes over the past year so figured the HPFP (with 110K miles) was on it's way out.

Log today indicates better behavior but still drops rail pressure to 500# and it stutters a bit, but no HPFP codes. So HPFP was getting weak so not a complete waste to replace it.

https://datazap.me/u/andyw/testing-n...zoom=2748-2883

Other data:

1. Car has been getting 3225 DTML Pump error shadow code since the morning of the same day I started getting the pressure drops to 37# but after 30 minutes of great performance. It is still randomly getting them but from what i have read, this should have nothing to do with it as it just tests the tank for leaks so I haven't correlated it but am willing to consider anything at this point.

2. Last fall I had the FPR replaced by a shop that was doing other work just to proactively refresh things. Since then the fuel gage doesn't read right (won't go above about 2/3). I've had it back to the shop and they said the FPR float switch on the one they put in tested bad and they replaced it again, free. But gauge still doesn't track above 2/3. Pretty sure there is an eductor in that assembly that multiplies LP flow too.

So I've ordered the DTML pump to satisfy my OCD. I am considering just opening up the fuel tank and checking every connection and routing for the LPFP and the FPR. Not sure what else it could be. I know I am not exceeding the walbro capacity because the above logs are a 92oct sub 400HP tune that I was running 98Oct fuel on. If that doesn't work I am going to borrow JPuehl spare LPFP and see if that helps.

Any advice on how to T/S this appreciated. Thx.

[iminhell1]

Phenolic washers on the fuel rail/bolts? If not, do it. It's been claimed to pretty drastically drop fuel temps and cure some odd issues.
https://*********************/thread...-gaskets.6305/


I've read numerous posts about replacing the filter/regulator assy and then the fuel gauge not reading correctly ... like everyone who's done the job LOL. I'm in that same boat. I did the Delphi unit from FCP.
From what I've been told it's a correlation error between the replacement unit and the fuel pump module. If we could get access to the FPDM there's probably an offset in there that needs changing, like coding a new battery.
It's an annoyance but affects nothing else.

Far as pressure's.
I'm still believing that all the futzing with the FPDM aren't the answer. It's the actual fuel line size that's the problem. It's the restriction and is causing a higher at the pump pressure, which raises demand. remember the LP sensor is on the rail. Nothing is measuring head pressure at the pump. And when you go with a big ass pump that is probably being over driven all the time, all it's doing is heating fuel and spitting it back out ... and therein comes the DTML issues and higher vapor pressures.
But I have no hard evidence to back this yet.
And again it's a case where if we could code the FPDM we might be able to fix problems.

Also, nothing says the pump isn't leaking.
(just the quickest video I could find)

[AndyW]

So, fuel level issue was one of floats being stuck up. So that's fixed. Still getting dropping rail pressures and a

2BE9 - Cylinder injection cutout: Pressure too low in high-pressure fuel system

code and attendent limp mode. Looking at the logs it may be correlated with a sharp left hand turn on the track (3A at Pacific Raceways) which means all the fuel is sloshing to the left. What i need is help understanding exactly how our fuel pump bucket (passenger side) and fuel pressure regulator and eductor (drivers side) work as a system so I can troubleshoot further. This is new behavior post HPFP replacement and the car didn't have these issues last year with the same LPFP and FPR. And, I don't recall issues after the FPR replacement earlier this year. So if anyone knows of a primer on how this works or has experience with this, I'd appreciate an assist. Throwing parts at this thing isn't working and it's starting to get frustrating missing out on scheduled track time (because you can't stress it on the street like you can on the track and it's running fine on the street). TIA.

[iminhell1]

Well here is what the complete system looks like out of the tank.
Small tan are feed to the filter.
Large tan is return, supposed to dump back into the bucket.
Black is a vent lines.

[AndyW]

Originally Posted by iminhell1

Well here is what the complete system looks like out of the tank.
Small tan are feed to the filter.
Large tan is return, supposed to dump back into the bucket.
Black is a vent lines.

What are the two middle assemblies?

Also, the black line from the VPR also feeds back to the bucket next to the tan. Wonder why?

[iminhell1]

EVAP things. There's no power to them. Simply valves based on vapor pressure. They vent out to the charcoal canister.