I started a new thread a little more specific to my no start problem....


I spent all today (re) doing electrical checks on my 89 GTA that won't start. Everything checked out fine except for I found an injector that had almost no resistance... #3 had .8 ohms!

the other 3 on the bank had 16.1,13.2, and 12.5

the other bank had 16.2,16.4,16.1,16.1


I actually got the car to run a couple of weeks ago after changing the computer and the Memcal at the same time. The car ran great for about 8 seconds, then died. I can now only get it to fire briefly after I pour gas directly in the plenum.


My question is:

Could the very low resistance injector cause the original ECM to go bad(short out), and could it cause the second ECM/Prom to short out in less than 10 seconds? I understand the injector circuits are somewhat fragile

I have ALDL + TTS. Unfortunately I was not taking readings when I changed the to the second ECM. I currently do not get any injector pulse width.


I have spark, TPS fine, Coolant sensor ok, O2 sensor new, I have dist ref pulse to the ECM, fuel pressure ok, new fuel pump, new distributer, new fp relay, maf diagnostics and MAF relays check ok, and yes...I checked all the fuses.


If anyone has any suggestions, please let me know.


Jeff

 

Yes, a low resistance injector coil can damage the sinking output transistors in the ECM. The INJ fuses should blow first, however. Verify that you have a 12VDC source at both sides of the injector harness with the ignition ON. Remove the electrical connector from the failed injector. Try cranking again.

If I am correct, the logic side of the ECM should show an injector pulse width independent of the actual output transistor(s). If you have on pulses, the ECM may have been detecting the output short circuit and shut down the outputs to protect them. This should have been revealed in the POST and flash of the MIL when the ECM was first powered up.

 

I can't believe it was so simple. I read Vaders advice to try to start the car with the one bad injector disconnected (I first reset the ECM) , and the car started right up (a little rough on 7)...unbelievable. The car has been sidelined for 2 months now.

The reason that it was so difficult for me to diagnose was that the car was running up until the Fuel Pump went out, and after I replaced it I had a seperate unknown problem.

It all started to make sense now that it must have been going bad for a while since I read posts on the relationship between a bad injector making a car difficult to start when hot. That was an intermittant problem right before the FP failed.

I wonder when the Fuel Pump failed, and having the Fuel system run out of fuel while the car was hot, could have somehow triggered the bad injector completely to fail at the same time?

I think it might be a good idea to swap out the 12.5 and 13.2 injectors at the same time. I suppose I will check on eBay first since I just found out they are like $80 bucks each (ouch)

Thanks Vader!

 

You may want to get a set from eBay or a recycling yard. Send off the replacement set for cleaning and flow-matching, then plan a good day of downtime to replace the set.

I've been able to get an entire set of injectors, rails, and regulator from a bone yard for less than $100.

 

yea man i had the same problem,

i was doin a top seepd run and as i just shifted into 5th and it cut out completly...from 130 down to 0 i had no power...

i finally got it running and any more then 1/16 of a inch throttle depression would cause it to choke out..

after 3 ECM's and a mess of other crap..i finally found a dead injector