Aftermarket fuel system diagnostics

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Oct 16, 2020 | 12:19 PM

shitbox

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Teching In

Joined: Jun 2017

Posts: 48

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From: vegas

Aftermarket fuel system diagnostics

Ok, I went to go get my car tuned. He declined telling my my fuel system is unstable because I needed a check valve on the return side so it would maintain pressure after the engine is turned off because it would slowly drop to 0psi (30-45 seconds)

so, I added one and still losing pressure..... not as fast as beforehand, but still not satisfactory.

my fuel system:
- in-tank walbro 450 feeding a surge tank via -6an line
- twin 044’s In surge tank with feeding check valves on the output of the 044’s......connected to a Y with a single -8an feeding filter and -8an feeding the drivers side rail
- 8an crossover at the front of the rails
- boost referenced fuel pressure regulator at the end of the passenger rail (pressure set at 60psi)
- return line is -6an
- in-line 60psi high speed check valve on return -6an to surge tank
- -6an from surge tank overflow back to main tank

no leaks anywhere that I can see or smell
check valves on both lines to “lock the fuel” at a certain pressure

Any advice/where to start?
Maybe start by blocking off return and pressurize to see if the checks on the 044’s are leaking?

HIGHLY doubt injectors are leaking.
seimen deka 80’s

the system is only holding 10psi

pics of fuel system:

In take 450 with 6an feed and return

Twin 044’s with check valves on output

Dual -8an connected to Y

Fuel rail setup

Regulator only holding 10psi

Last edited by shitbox; Oct 16, 2020 at 12:27 PM.

Oct 24, 2020 | 06:02 PM

stevieturbo

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Joined: Nov 2003

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From: Norn Iron

Who gives a **** whether it holds after shutdown ? Is your tuner trying to tune the engine with it switched off ? lol

And they look like some Chinese shitty check valve on top of the 044...not needed at all.

Is fuel pressure stable when driving, does it behave as expected with boost ? Is it repeatable ? If the answer is yes to all those....then it is working, and shoot those shitty check valves at this "tuner" from a large catapult.

Oct 31, 2020 | 01:46 PM

imma_stocker

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Joined: Apr 2007

Posts: 1,155

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From: Country

Exactly, I have no check valves in my fuel system. Key On - spike to 53psi rail pressure then immediately falls to zero.

Only fuel problems I have are due to not driving the car enough.

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