ST205 GT-Four electrical issue

[GT4 20]

Not my car, fortunately, but....

Rebuilt engine has just been put back in and went to fire up. Ran for about 20 seconds before it would shut down. No engine check light present.
Still have injector pulse and spark present - fuel pump is shutting down.
Engine will run fine if fuel pump relay is bypassed.

Worried that ECU itself may be the problem. I have a spare we can try but wondering if anyone has any suggestions in the meantime?
Chers
Gary

[gepsk8]

earths are tight?
fuel pump relay?
is the ecu putting a signal out to the relay? as sounds like it used up the pressured fuel and fuel from cracking it over. not been signaled by ecu.

[matt dunn]

earths are tight?
fuel pump relay?
is the ecu putting a signal out to the relay? as sounds like it used up the pressured fuel and fuel from cracking it over. not been signaled by ecu.

correct.

The relay has two ways of being turned on or energised.

(A) By a cranking signal, ( you will get fuel pressure while cranking even with no ecu)

(B) And by the ECU or AFM earthing out the FC feed from the relay.

Unplug the ecu, and with a test light earth out the wire that trigger the fuel pump, ( or if it has an airflow meter move the flap as there is a switch in the AFM that controls the relay rather than a feed from the ECU)

Make sure the pump runs. If it does you are looking at a ECU or ECU feed problem.
If not a relay or IGN supply to the relay problem.

Matt