A friend here in town has just got his T II motor rebuilt (s4). When he cranks it over it will fire up for about 30 seconds, and his wideband will show it lean out then die. It's got a new fuel filter, 720 primary 1000 secondary. He thought it may be the fuel pump (stock t2), but another guy brought his fuel pump from his car (known to work), and the same symptoms occured.

I tried to crunch some math on how many lpm the injectors were using vs. the output of the stock t2 pump (read it puts out 190lph). I came up with the injectors using 3.44 lpm and the pump putting out 3.16. Of course this cant be 100% right, because from what I know the injectors are not at full duty cycle.

Any ideas what to check next?

 

What are you using to control the fuel? I hope it's not a stock ecu. Also what's the % of your injector cycle at idle, or where do you have your starting fuel crank at? What ecu/program.

 

if you have deleted the airflow meter for aftermarket ECU,, you may need to bridge the safety circuit at the AFM wiring
-- or instead use the new ECU to swing the earth of a new fuel pump relay for the pump

if your still using a stock type ECU,, then i would suggest the issue is with the two speed fuel pump circuit near the headlight,, turbo side

-- at any rate,, all improved output engines should have this 2 speed circuit bypassed
,, and even run a relay and new wiring,, its particularly temperamental

-- i have seen the full voltage side read as low a 7 V due to deterioration of the circuit

but i believe yours may be stopping when dropping onto a faulty low speed circuit
-- or that factory AFM safety trip is cutting in