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Thread: Two injectors not firing?

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2011-08-25 12:59:48
Two injectors not firing?
Having an issue with my DET swap, I have narrowed it down to fuel, injectors on 1 and 3 do not fire. I have determined this by cranking on the car with the fuel rail off and holding it over a rag. I can switch injector plugs over from 2/4 to 1/3 and the injectors fire fine so I know the injectors are in working order. I have not been able to check pulse yet, from reading on the internet I connect one lead to the positive end on the battery and then other to the ground on the injector harness and crank the car, correct? Odd thing is when I switch over to my old calum ECU and crank it 2/4 fire right away and then 3 comes online about a second into cranking, 1 stays off. I have my stock 99 ecu that I will try when I get home from work but what should I be looking for if I do not get a pulse? Also cranking it so much is draining my odesy battery quite quickly, can I pull the dizzy and turn it by hand when the car is in 'on' to get the injectors to fire?

STi injectors at 4bar
JWT ECU tuned for this setup
2011-08-25 23:16:51
So I'm not getting pulse from the ECU. Random thought, will I have grounding issues if the ECU is not bolted down?
2011-08-25 23:20:31
no you wont have grounding issues mine sits on the passenger floor. have you checked the wiring itself that leads up to the injector clips? I know these old harness like to become bridle and break over time.
2011-08-26 05:19:24
Ok so, I get a weak pulse from my ECU, checked all the wires, swapped my dizzy, checked over all my grounds and still can't get 1 and 3 injectors to fire. Anyone have any input on this?
2011-08-26 05:28:53
The wires like to break under the insulation. Best thing to do is to test at the pins for 12v positive and make sure you have it. If not then you probably have a broken wire somewhere. Again its not gonna be broken in half, Gotta tug on them to get them to break the insulation where the copper wire is actually broken at.

Next if you have 12v at all of them is to continuity check from the clip to the ecu and make sure you have continuity all the way there. Again just give each wire a good tug where the old original harness is usually breaks where it comes out of the main loom that has the hardened plastic over it. Most of the time just before it goes into the stock clips but im assuming you wired up the subaru clips so probably just before where you soldered or crimped the connections. Its a pretty simple circuit really. Not much to it.
2011-08-26 05:39:45
I have a common 12V across all of the clips, I also have continuity all the way from the clips to the OBD2 plug. The issue is the ECU is not sending a pulse to 1 and 3.

99 Stock 99 P11 ecu = injectors 2,3,4 fire, 1 does not.
97 B14 calum basic = injectors 2,3,4 fire, 1 does not.
97 B14 JWT ecu = injectors 2,4 fire, 1 and 3 do not.

Odd thing about the calum and the 99 p11 ecu is that 3 comes online about a second after cranking, with the JWT it does not. Also I do get very weak pulse from 1 and 3 from the ECU when cranking, guessing not enough to open the injector. I have a hard time believing that all three of my ECUs have gone bad.
2011-08-26 05:47:11
nope bad connection somewhere. Guarantee it. Whether it be at your soldered or crimped joint or in the factory harness. Again when you have a break under the insulation at times they will be barely touching but enough to cause random misfires or a full on misfire. Again no way its an ecu problem.
2011-08-26 06:01:28
Why am I only getting a weak pulse from the ECU then? Bad ECU grounds?
2011-08-26 06:02:35
You will hardly even see the pulse. Again a weak signal at the injector could mean a practically broken or broken wire.
2011-08-26 06:09:26
No I get a weak signal AT the ECU from cylinder 1 and 3 which is leaving me scratching my head.
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