my secondary injectors are not firing, need help on why they are not?
i've checked:
crank angle sensor
injector resistance

they all seem to be ok. its a s5 turbo in a 90 n/a, I believe they did work when firt installed. any help would be great! thank you

 

Might want to take em out and check them or clean them.

 

take em out and run 12v through em, do they click?? If not, get some new injectors.

 

took out the 720s and put the stock 550s back. now my question is: the haynes manual says to listen for clicking above 3800 rpms. would it be a clicking or more of a buzzing at that high an rpm?

 

Were the 720's high or low impedence? Low? Then you might have smoked the injector drivers. They are located in the ECU.

 

i think low. is there any way to test the ecu? or fix? or will i need a new ecu to try and hope thats the problem?

 

How are you proving they aren't working? You need to test at load, above 3800 RPM.

 

I unpluged the vacume from the boost sensor, took it up to around 5000rpms and listened for a clicking at the injector with a stethescope.

 

That won't really work. Does the car bog down at 3800 RPM?

 

i can ease it all the way through the rpms, but under boost it bucks bangs and pops!

 

The manual does have a valid test where you disconnect the vacuum line off the boost/pressure sensor , plug the vac line and listen for clicking above 3500 rpm.

It sounds like they are working but have some type problem when they come online.

The cheapest first thing you might do is make sure the orfice is in the boost sensor line. The part number is on this site somewhere. You can make your own by using the descriptions given on this forum SOMEWHERE. You might do a search for PILL or ORIFICE. It is called a orifice in the parts manual though. It's just a piece of plastic with a very small hole in it to dampen surges to the boost sensor.

If you had a meter and wanted to check the secondarys, you could back probe the secondary injector wire at the back of the small ECU plug, and watch for a voltage drop at 3500 rpm. The voltage would be approx battery/alt voltage until then and once 3500 is reached under load, the voltage will drop dramatically to say, 8 vdc or so. I forget. It depends on load. With the vac line off it will happen each and every time you hit 3500, load or no load.

 

I forgot. If they are low impedence (the 720), you NEED to put a 10ohm resistor in line to them or after them. The drivers in the ECU need to see this 10-12ohms approx or they will get too much current and kablooi. No more worky. Chances are they are not blown. It takes some time for that to happen, hopefully.

Another way to hear the injectors click would be to pull the ECU plug off and put a ground on the injector wire your interested in. The ground would be put on the PLUG not the ECU'S jack. And just for a second or two, just to hear the thing go click each time a ground is put on it. Clicks once each time the ground is put on the wire. You'd do that with the engine not running of course. Just key ON

 

unplug the boost sensor and use a test light hooked up to the + on the bat. and stick the probe in the black wire in the injector clip and run the rpm's up to 3800 if it flashes plug it in
and plug the boost sensor in check it agian if no flash the boost sensor took a ****

 

Have fun doing that with a TURBOII. You can't access the injector plug on a turboii.

In the driveway, the secondarys only operate IF you disconnect the vacuum line FROM the boost sensor. If the secondaries come online WITH the vacuum line connected, THEN the boost sensor is kaput. PUlling the vacuum line OFF simulates LOAD.

 

thanks for the info hailers. i have the orfice in the line, but it wasnt in when this problem started! i guess i will try to check the injectors at the ecu. i have a feeling its going to be something with the ecu. this car seems to like my money!

 

ends up it was boost leak this whole time! had a slit in the underside of the elbow at the innercooler. thanks everyone