1981 c20 tbi swap no injector pulse HELP!!!

:banghead: I just installed a used Tbi on my 1981 c20 5.7,from a 1990 suburban 4x4 1/2 ton.My problem is it cranks over and will only start if i pure fuel into the throttle body and run for a second then stall out,I have 12 volts going to the injectors when the key is on.but it won't start.Do you think this ECM has a VATS thats causing me a problem?The Tbi did work well in the suburban before i took it out.I also tried another ECM out of a running 1990 chevy 4x4 pickup with a 5.7,still no pulse but still got 12 volts to the injectors,some how im not getting a ground? I unplugged the injectors and hook up a 12 v light to it,cranked the motor and the light wouldn't work.

Maybe a dumb question but what's your fuel pump doing? I assume you swapped out sending units and so forth but do you have fuel pressure?

Also, when checking the injector pulse without a noid light, use an LED for it's speed and low resistance.

-N8

Hi Madcatter I installed a external electric fuel pump and filter to the original fuel lines I have fuel to the TBI,but I need to check how much pressure is going to the throttle body,the fuel pump says it max is 15 pounds,but i will check it when I get back from my sons Soccer game.There is fuel coming back to the Fuel Tank from the return line I can see that,but do you think low fuel pressure can stop the injectors from pulsing?

I'd say 15psi should be just fine IF that's what's actually getting up there. Also, the pressure regulators are known for going bad, especially the spring. Cheap and easy fix though but you'll have to pull the throttle body and disassemble it to find out. There's lots of info on this procedure out there. I just did it last week on my '90.

-N8

Hey MadCatter Thanks for your time,I got it running,I needed 12 volts to the orange wire in the Harness and it fired right up.Don't know how I miss that one.