boughternewin92

hello all. I'm new here so please excuse any errors that i may make. I have a 1992 z28 with about 62 thousand miles that has not been driven for about four years. when I tried to start it i put in a new battery and she fired up right away. There was a full tank of gas when it was parked so i drove it to use it up and replace it with new. after about 80 miles or so it became harder to start each time until finally it wouldn't start at all. I siphoned out all the gas i could and replaced it with 10 gallons of premium and added a can of seafoam and changed the fuel filter. didn't help. checked fuel pressure and volume, looks good. changed distributor cap. rotor, and module, new plugs and wires. cranks good and sounds like it wants to run but doesn't catch. removed injectors and tested each one. they spray a perfect pattern. after trying several times to start it. the new plugs look a bit sooty and the spark color looks a bit orange. thats all i can think to try. any help would be very welcomed. Forgot to mention that I also changed the coil.

ws6transam

I would back up a bit. Re-check the fuel pressure. If it's good, then either there is an ignition problem or else the ECM isn't properly firing the injectors, or the injectors are clogged from sitting.

Re-check your ignition. Make sure the plugs are routed properly by tracing each one back to it's post on the distributor. Check the cap, make sure everything is plugged in properly, and that the coil is also plugged in correctly. Make sure that the rotor is pointing at the #1 post when #1 cylinder is at top dead center. If that all checks out, attach a spark plug to #1 plug wire and clamp the plug to a ground point somewhere. If you get a nice clean spark, then it's likely not the ignition.

Does it fire up with a squirt of ether into the plenum? If so, and you are sure you have good injectors, and good fuel pressure, then maybe you might want to drop the ECM, un-plug it, re-seat the prom, and re-install it.

boughternewin92

thanks for the reply ws6transam.rechecked all the things that you suggested except the ecm. starting ether in the plenum made a terrible noise but no start.
I also notice that the fan comes on as soon as the key is turned on and someone told me thats not right either. I changed the coolant temperature sensor but that didn't seem to do anything. I'm a little reluctant to mess with the ecm so maybe the fan on symptom will help you to figure out what else might be wrong. if not I guess i'll just have to try the prom thing.

Injuneer

Have you scanned it for codes? It isn't unusual for the ECM to turn the fans on when certain codes set. Easy to scan, by shorting pins in the ALDL connector. This is the pocedure for a 93, but your 92 should be the same:

http://shbox.com/1/dlc2.jpg

boughternewin92

I did scan for codes and there are none. i only get the one two- one two -one two which i believe means no codes are present. while reading all i can find on the injection system, it seems that 4 injectors are connected together on the left and the other 4 on the right. if this is correct, how does it know which of the four should fire or do they all fire together? i ohm checked one to the other and they are indeed common to each other. thanks for the reply

ws6transam

The third-gen cars are all batch fire which means it shoots all eight injectors simultaneously. Two injector drivers are present in the #730 speed density ECM, and they handle four injectors apiece. Try checking to see if the A/C is engaged; If so, as I recall, the electric fans may be forced into the on position. Just flip the switches to off and re-check the fans. Otherwise, I would still suggest that you pull the kick panel in the passenger compartment, remove the two little machine screws, drop the ECM, unplug it from the harness, and re-plug it in to see what happens. Just be gentle. It might, or might not help.

Lastly - what does 'big noise' mean, when shooting ether into the plenum, then trying to start the engine? If you have a good ignition source, the engine should fire up momentarily for about half to one second.

boughternewin92

good to know about the batch firing but if the intake isn't open on all the other cylinders but one then where does the fuel go? also did one other check. I ohm tested each injector and they all read about 16 ohms except number 5 which read only seven ohms. The "big noise" it made sounded like a pre-ignition knock or ping but was quite loud

boughternewin92

WOW!!!! I unpluged the injector that read low resistance and it started right up...It ran a little rough but but i suppose it will be ok when i put a new one in.
Thanks again for the help and i hope others can learn from my experience. my guess is that the low resistance shorted the firing signal to ground so the other injectors failed to fire also...

ws6transam

EXCELLENT! Yes, you are right - If one injector is shorted, it'd take out the three other good ones by shorting the injector driver. Great troubleshooting! Good luck with replacing that injector; I suggest ordering yourself a whole set of fuel rail o-rings as a kit and replace all of them at the same time. Sometimes the older o-rings will leak when you disconnect them. I don't think they are that expensive; At least I hope not, because I tossed out a couple of boxes of new ones about a year ago. Sorry, but I got rid of all my old TPI stuff.