MK1 Golf GTI - Low voltage at fuel pump when cranking

Hi

Ive been struggeling a looong time with bad cold starts (In the mornings etc)

My cold fuel pressure is set correct at around 2 bar

But ive noticed that my fuel pump is only getting 9v when cranking.

I then checked the fuel flow volume from the return hose, looped my fuel pump relay and meassured the volume after 30 seconds which was half of what it should be. (Correct volume is 0.9L and i only got 0.4L)

After that i connected a direct 12v battery to the fuel pump and meassured it again over 30 seconds, and now i got the correct volume.

So something tells me that i should be getting more than 9v when cranking, and thats the reason of my bad cold starts?

Anyone able to help me out ?cf_emoticons__BangHead:

swap the 17/18 relay into the fuel pump position, if voltage improves try a new fuel pump relay. it may be worth openign the relay to see if there are any dirty/bad joints that can be fixed

if it doesnt help check voltage to the fusebox while cranking, and check your battery cablign and wires to the terminals are all good

But shouldnt i be getting more than 9v at the fuel pump?

yes you should, hence why i say try the 17/18 relay, see if voltage improves

if not, then it would likely be power problem to the fusebox, hence the battery cabling tips

With the 17/18 relay it didnt help the voltage.

Battery clips are all new, and re-checked them, should be OK

Sidenote it that if i pull 12v directly from the battery to the fuel pump i only get 10v when activated.

So i would guess my issue is my battery.

cool yeah i would start there, perhaps it has 12v when tested but with any load on and it drops too much