1G fuel injectors not pulsing

[wrxtacy2003]

So i bought a 91 gsx that was not running. I have been diagnosing the no start and found out that the fuel injectors just aren't spraying fuel. I have fuel and fuel pressure in the fuel lines and rail. The car also has spark. I checked the resistance of the injectors, two are bad and two are good, obviously the two bad ones won't work, but i can't get the two good injectors to pulse. I opened the ecu and it doesn't look like anything is fried or burned out. I am out of ideas, i have a haynes manual and did all the steps related to electrical fuel problems. No help. The resistor box is good, i checked it with my DVOM, plus my friend just used it in his honda to see if his resistor box had gone bad, and his car ran fine with it.

 

[redyute1]

did you check the relay

 

[wrxtacy2003]

yea. It clicks once when i crank the car, then clicks once more when I stop cranking. not sure if that means it's good, but that's what i got. When i ground the injectors manually they open and spray fuel, so i figure it's either the ecu or the relay, and i have no one to swap an ecu with to test that out.

 

[manrightchea]

The injector resistor pack provides the positive to the injectors. I would buy a 12v tester or multimeter and check for 12v at each clip. The ECU grounds each injector wire on a given sequential order that is determined by the crank angle sensor on the head. The crank angle sensor determines when the coils and fuel injectors fire, similarly to how a distributor determines spark. If you physically want to test the CAS, you can pull it from the head and spin the keyswitch. If you do this, be prepared for backfires and make sure that you set the motor and sensor at TDC when you reinstall them. This is easy to do, and I will help you do it if you don't quite know how to do it. But if you ground them yourself and they fire then I would look at your ECU, as it grounds the injectors. Just for future reference, a 1G ECU can look fine and still be bad. When capacitors leak, it may not necessarily be visible. Its not until the condition is very bad that the capacitors smell and the fluid they leak is easily visible. Let us know how it goes.

Oh yeah, the 1G's have a MPI and some other important relay (it may be the fuel pump, but don't quote me) located near the positive battery cable, as well as a ENG fuse in one or your fuse boxes. I doubt these things would have anything to do with your injectors pulsing ever. The CAS and ECU determine when they fire so check those first.

 

[wrxtacy2003]

i am for sure getting power at each injector. They are just not getting grounded out. I did not know the CAS is used to determine when to fire the injectors, this gives me another path to try out. I'm pretty sure the relay is good, because it clicks and that's what i'm told it is supposed to do. So now it leaves me with the ecu and the CAS. Thanks. I'll see where i get from here.

Dustin