ATX 12V drop (yes another ATX PSU thread)

[racitup]

I'm trying to use the 12V output from a 350W ATX PSU (Novatech Powerstation 350)
It is apparently capable of sourcing 30A @12V but am struggling to get 5A.
When I connect the load (it's a 12V car tyre pump, don't know of the inductive/noisy load will make a difference?) the voltage drops from 12.2V to about 4V and the current draw is 5A.

EDIT: The sticker on the pump says 12V 10A (The pump should be drawing around 6A I think)

I've read that I might need to have a 5V load, so I have tried charging my phone from both the 5V and 5V standby lines at the same time as the 12V load and it makes no difference.
I also read about voltage sense lines, but can't seem to find any reference on the ATX pinouts.
The only other connections I have made are tying green to black to make the PSU permanently on.

Any ideas how I can get the output stable?

[strawberry]

soft starter for motor
capacitor bank
something that limits peak current below 30A
with oscilloscope could capture current waveform

[Phil1977]

Can you try connecting a smaller and non-noisy load like a 20W and 50W halogen lamp, e.g. from a car replacement set?

If the 50W halogen lamp is lighting up instantanously then you know the supply is able to deliver >10A.

[racitup]

Lol, thanks for the replies.
Having messed about a bit more and taken some voltage measurements from the PSU end it turns out it was the connections.
Apparently you can't just try and put 10A through some crocodile clip connections and hope for the best!  

Replaced it with proper plug/sockets, wire and solder connections and worked fine.

I was just trying to recharge my unvented hot water cylinder expansion tank using a car tyre pump. Back up to ~3bar