injector 1 and 6 not firing

[sneakypete]

just finished my build and ive been having problems with a rough idle and its missing. didnt think it would be my injectors (RC 550) since i just got them back from getting clean and flow tested. turns out that 1 and 6 arent firing.
been searching and havent come up with any results.
so far ive check the resistance on the injector and wiring, the injectors do have 12v with key in on position, ignitor has 12v, coils wires and plugs check out ok, timing was reset and set again. cant figure it out.
if anyone has any ideas, please let me know
-pete

 

[suprafanatic]

spark plugs?

 

[92TealSupra]

What about your cam position sensor.

 

[hvyman]

cyl 1 and 6 share the same coil. its the left coil test it if not i bet its plugs

 

[sneakypete]

coils resistance check out ok. i didnt check out if its getting voltage... ill check tonight. but i didnt think the coil is responsible for powering the injector itself. the spark plug is getting spark. its just that the injector is not pulsing when the car is running.
-pete

 

[hvyman]

o i c. maybe a wiring problem. are the connectors on the right injectors?probally but double check. maybe just bad injectors try swaping them and see if the problem is the same

 

[sneakypete]

i rewired the injector clips and they are new. they get 12 volts with the key in the on position. injectors were sent to rc to get inspected, clean and flowmatched. i tested them and they are all within spec.
i believe they arent getting the signal to inject fuel since injectors 1 and 6 are a pair and should be spraying the same time.
my research is leading me to believe that the ecu is bad. but i would have thought that if it was the ecu, then none of the injectors would be getting the signal.
-pete

 

[bluezone]

if you have an early mk3 86.5-88. check the resistor pack for the injectors. its on the drivers side fender. there are 3 resistors in the pack each one wired to 2 injectors. if one burns out 2 injectors go dead.
they are part of a grounding system so you would still show power.(12volts).

 

[sneakypete]

i tested it and also tryed swapping it out with a buddies resister pack that worked.... no change

 

[ilikebigbutts]

Do you have power AND ground at the injector clip?

forget the DMM does it light up a test light or better yet do you have a head light bulb laying around that you could use to load the circuit?

Check the circuit while the car is running/cranking?

I believe the circuit is low side driven which means the ecu opens/closes the ground side of the circuit to pulse the injectors.Can anyone confirm?

if the circuit checks out swap injectors around...

 

[Blade2001]

How did you connect the new injector clip to the car's wiring? Hope not crimb connections. You need to solder those..

 

[jdub]

Proper crimps are as good or better than solder...at lot less brittle and less prone to breaks.

 

[sneakypete]

Do you have power AND ground at the injector clip?

forget the DMM does it light up a test light or better yet do you have a head light bulb laying around that you could use to load the circuit?

Check the circuit while the car is running/cranking?

I believe the circuit is low side driven which means the ecu opens/closes the ground side of the circuit to pulse the injectors.Can anyone confirm?

if the circuit checks out swap injectors around...

i check for power at the clips, but didnt not check for ground. i will check in the morning.
DMM??? yes i have a headlight bulb laying around. what should i do connect it to?
i rewired the injectors with brand new clips and soldered the connections to answer the other guys question.

-pete

 

[sneakypete]

i tested the voltage while the car was running on injector number 5 which works and compared it to the voltage on injector number 6 (not working) and they are the same. i also tried switching the clips 5 and 6 while the car was running and injector 6 was still not injecting. i thought that it will still inject fuel even though is was not at the right time.

i just dont get it. everything is just leading me to believe that injector 1 and 6 are dead. how could that be since i just sent them out to rc for inspection, cleaning and flow matching.

how should i check for ground on the clips? i tried with a voltmeter by putting the positive on the battery and the negative on the clip with the key in the on position. what should i look for?

the only thing i havent tried is swapping ecus. anyone think that the ecu could be bad?

-pete

 

[ilikebigbutts]

How are you sure 36 didnt fire when you plugged in #5 clip?If it really didnt fire then you got bad injectors, simple as that...have you pulled a plug?what do 1 and 6 look like?

DMM=digital multimeter...

 

[sneakypete]

yea... injector 6 didnt fire when i plugged in number 5 injector clip. how did 2 injectors go bad immediately after i got them back from RC?

 

[IJ.]

Is the ground strap from the Coil pack to the head there?

 

[sneakypete]

yea, but i had to move it the fuel rail because the valve covers were painted and it wasnt a good contact. but its been grounded like that for a few years and i didnt have any issues before that.
thanks

 

[IJ.]

Sandpaper the terminals where it grounds to the head (the rail is insulated)

Have you verified that the Injectors aren't firing?

 

[sneakypete]

how else could i verify that they arent working?