VX V8 LS1 fuel pressure regulator, on the rail or in the tank? fuel pressure issue.

[RSS570]

Hey guys,

I have a fuel pressure issue with a VX SS LS1 V8.

Fuel pressure is low on the gauge when tested and as soon as the pump stops priming the fuel pressure drops rapidly.

Is the pressure regulator next to the fuel pump in the tank or is it on the fuel rail on the passenger side of the motor?

I have read the fuel pressure dampener is on the fuel rail, or is it the regulator?

Has someone else had this problem and resolved it?

Thanks for reading.

 

[kais3r]

regulator is usually on the fuel rail, undo the cover and look for the rail, it'll be a cylindrical bulb on the end of the rail.

 

[kais3r]

Pressure drop when off is most likely the regulator, best place to start, I assume it hesitates to start after sitting overnight?

 

[RSS570]

In the fuel pump assembly inside the fuel tank there is a steel cylinder connected to the return line, is this the regulator for the V8 LS1?

 

[Sabbath']

Regulator is on the return, in tank.

 

[RSS570]

If the regulator is the unit in the tank what is the unit connected to the vacume line from the induction manifold that returns to the tank? (located under engine cover) It also has electrical connections?

 

[Big-Al]

that is the carcoal canister purge valve.
Another likely cause is the short length of plastic tubing that connects from the fuel pump to the swirl pot inside the tank. I have seen these split before resulting in the loss of fuel pressure and leak down that ur seeing.

 

[BlackVXGTS]

From the Holden Service CD:

" The fuel system used with the GEN III V8 engine is a ‘single line’ system, which means that the previously used fuel return line from the engine fuel rail, is no longer used. A changed design, modular fuel sender assembly is located in the fuel tank, that incorporates a fuel pressure regulator, a fuel reservoir, the fuel sender unit, roll-over valve and the fuel pump in the one modular unit. Apart from the complete assembly, the only other serviced component in the modular fuel sender is the fuel sender assembly.
Quick-connect fuel line fittings are used for all fuel line connections, including the modular fuel sender assembly, fuel vapour canister, fuel filter, fuel feed line T-piece and at both the engine and fuel tank ends.

1.1 GEN III V8 ENGINE MODULAR FUEL SENDER OPERATION
The fuel control system used on the GEN III V8 is a “Returnless” or “Demand” system. The fuel system starts with the fuel in the fuel tank. A single in-tank high pressure fuel pump with an integrated fuel pressure regulator (located inside a modular fuel sender assembly) is used. From the high pressure pump, fuel flows through a fuel filter, then back into the fuel tank via the fuel pressure regulator. Fuel is supplied to the fuel rail and injectors by a single feed fuel line.
The high pressure in-tank single pump is capable of providing fuel at more than 410 kPa. A pressure regulator in the modular fuel sender assembly maintains the fuel pressure at a regulated pressure of 410 kPa.
The fuel pump is energised by the PCM via the fuel pump relay The injectors, located in each runner of the intake manifold just ahead of the inlet ports to the cylinder head, are controlled by the PCM.

System Components - The Fuel Control System is made up of the following components:
• PCM
• Fuel Tank
• Modular fuel sender assembly, containing;
• Fuel pump assembly
• Fuel pressure regulator
• Fuel filter
• Fuel pressure supply line
• Fuel pump relay
• Fuel rail
• Injectors

 

[RSS570]

Big-Al you were spot on great answer, the fuel line between the fuel pump and the top of the fuel assembly unit had failed!
Now that it is replaced the car has stopped misfiring and has a great deal more power.

Also big thanks to BlackVXGTS for your extra detail explaining the system.

Cheers for all the responses. Stoked!!

 

[Big-Al]

No worries, had the same thing happen but I only problems with hard starting. Suspected the fuel pump check valve but turned out to be that tube.

Bit of a pain to replace but not an expensive part.