GM Guy Posted June 28, 2009 Report Share Posted June 28, 2009 Hey guys, hoping someone out there has some ideas or even experienced the same issue... Got a strange problem at hand, found a few other postings in the past with a similar issue but only saw one with a resolution (tried it, no go), others never posted their resolution. 1991 Z34 w/ the 3.4 DOHC, 84k miles, injectors won't open when cranking. All fuses are good, getting spark, 40 lbs at the fuel rail, pump sounds equally as strong, pressure doesn't drop when cranking, checked voltage from the DIS to the computer and showing voltage on the low and high pulse wires (black w/ red and purple w/ white) when cranking, replaced the crank position sensor (had oil in the connector), showing 12+ volts at the front three injectors while cranking. Also tried replacing the computer with a spare one I had from the junk yard that I have run the car on in the past trying to diagnose previous issues, also tried using the spare memory stick, but absolutely nothing. Also tried replacing the DIS with a spare one. The engine will run on starting fluid. Engine was running fine and just quit. Any ideas? Could a shorted injector cause an outage since they are fired in batches? I would figure half would still work? Quote Link to comment Share on other sites More sharing options...
GOT2B GM Posted June 28, 2009 Report Share Posted June 28, 2009 go to the junkyard and grab a fuel rail complete with injectors and swap it out Quote Link to comment Share on other sites More sharing options...
Crazy K Posted June 28, 2009 Report Share Posted June 28, 2009 seeing 12 volts in the injectors? you should be using a noid light, which should flicker on and off with teh pulses. you can "make one" with a tab style light bulb, such as the one used for the liscense plate light, by bending out the tabs to make contact with the injector connectors. yes, you could have a completely bad injector that is shorting everything out. you need to test them all with an ohm meter and post what the results are. oh, and if you unhooked the vacuum feed to the fuel regulator, would the pressure go above 40psi? Quote Link to comment Share on other sites More sharing options...
White93z34 Posted June 28, 2009 Report Share Posted June 28, 2009 Any ideas? Could a shorted injector cause an outage since they are fired in batches? Yes. I have had it happen myself. Pull the plenum and get a multimeter and ohm all 6 injectors. Quote Link to comment Share on other sites More sharing options...
GM Guy Posted July 1, 2009 Author Report Share Posted July 1, 2009 The culprit was a bad injector on #2. All the injectors including the bad one ranged from 12.6 to 12.8 ohms. Finally figured it out when I thought it might be an exposed wire on the harness and began disconnecting one injector at a time and trying to start, the engine would finally run with #2 off and would shut down the engine immediately when the connector contacted the injector. Thanks for the help! BTW, the metal section of the injector was burning hot after cranking several times while all the others were cold but never blew a fuse. Quote Link to comment Share on other sites More sharing options...
White93z34 Posted July 1, 2009 Report Share Posted July 1, 2009 I had the EXACT same thing happen on my old Euro 3.4. never blew a fuse, just would not run. Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted July 1, 2009 Report Share Posted July 1, 2009 BTW, the metal section of the injector was burning hot after cranking several times while all the others were cold but never blew a fuse. Based on what you mention here, I'd replace the injector fuses. If the fuse doesn't blow for a short, the next thing to go will be the driver circuit in the ECM, and that is definitely more expensive than a fuse! You may already know this, but the rating given to a fuse isn't actually the amperage it will blow at, but the amperage it is is designed to handle without blowing. The actual current required to blow the fuse shouldn't be substantially higher, but often is. Anyways, glad you got the issue sorted out! Quote Link to comment Share on other sites More sharing options...
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