2.8 v6 won't start/not getting enough fuel - Pump or relay?

[VAG-Slag]

My 2.8 v6 isn't wanting to start at the moment, I have scanned it and the only code I seem to be getting is 17972 (Throttle Actuator - under voltage during basic setting - Intermittent), which I suppose could just be from me pumping the throttle while cranking?

It's got an external in line fuel pump, which was noisy as hell when I bought the car, I know they're pretty noisy as it is but this sounded quite rough...

I took the fuel feed to the fuel rail off - When I turn ignition on nothing comes out (should prime, no?) and when I crank it over there's the occasional spurt of fuel (guess it should be constant while cranking?)

I did just about get it started but it was clearly struggling for fuel, lumpy as hell and cut out after 30 seconds or so.

Guessing it's either the pump or the relay, would be keen to hear which one your money would be on based on the above?

Thanks in advance chaps!

 

[aragorn]

Is there actually fuel in the tank

 

[VAG-Slag]

Is there actually fuel in the tank

Well, here's the thing... It's doesn't have a fuel tank!!!

It's got an ally fuel cell in the boot, with the pump straight off that. . . When I picked up the car in November last year, we drove it on the trailer no problem, but when we got to the other end (after towing it through a storm!) it wouldn't start. With the cell being stuffed with sponge (as per MSA regs) you can't even look to see if there's any fuel in there. I stuck 5 liters of fuel in at the time, which didn't seem to help but we eventually got it started and drove it in.

Since then the car has only been run up to temp maybe 3 or 4 times, so I highly doubt it would have used 5 liters since then!... But obviously it needs to be ruled out. . . When I'm next down the yard I'll remove the fuel line from the cell and see what (if anything!?) comes out...

 

[aragorn]

I presume theres no in-tank pump, and its a gravity feed to an external one?
Stick 10 litres in it and see how you get on. If its properly empty, 5L might not be enough to actually prime it all, especially when you consider the volume of fuel in the lines, rail, and whatnot.

I did something similar with my track car. Tank was open to the air for 2+ years and was bone dry. I fitted a pump and put a gallon of fuel in it. Car started and i moved it around, but after shunting it about the drive and warming it up etc, usual messing around, it stopped starting. Chucked another 5L in and off it went.

To check for relay issues, stick a volt meter onto the fuel pump fuse (or the wire at the pump itself) and see if your getting 12v while cranking.

 

[VAG-Slag]

Is there actually fuel in the tank

Just an update on this............. No

Took the feed to the pump off and it's literally bone dry. . . It must have all evaporated through the tank breather over time!

Thanks for your help either way... Maybe in the future I'll block off the breather while it's parked up