im having trouble getting my 86 corvette to start... it is cranking has spark and has fuel to the rails but injectors aren't delivering fuel

 

An 86 has a cold start injector, I'd check power to it. You could also check power to the injectors and if the ECM is grounding them.

 

we tested voltage to them if we use a frame ground we get 12volts.. if you put a probe on each wire should u get a reading?

 

If you put a noid light or test light across the unplugged connectors, it should flicker during cranking.

 

ok will try that .. if that doesn't work im thinking ecm problem

 

The injectors receive pulses from the ECM through a fuse on each bank. The injectors have a coil and one coil wire goes to 12v and the other wire is pulsed to ground by the ECM. First check the fuses with an ohmmeter. Buy a noid light from an auto parts store or make one with an LED (light emitting diode) and a series 680 ohm resistor (both available from Radio Shack) and connect the light across the plug from an unplugged injector and see if the LED pulses during cranking. The homemade noid light must have the correct polarity on the injector plug. If you have spark, then you should also have injector pulses. If you have pulses to the injectors, spark, fuel pressure, then check for constant fuel pressure during cranking and check for fuel pressure holding for a long time after the ign is off. Also, try spraying starter fluid into the MAF during cranking to see it will start. Measure the resistance of each injector coil, they should be about 16 ohms. A better measurement would be to measure the inductance and Q of the injector coils, but this requires an impedance bridge. Very low resistance on only one injector coil on each bank will prevent all the injectors on that bank to pulse.

 

ya they are around 16 im pretty sure they aren't pulsing but i won't get to check until tomorrow because of a storm

 

An ohmeter is a very poor test, the impedance bridge will find a coil with a turn to turn short which will load the bank and prevent all the injectors on that bank to work. An ohmeter cannot find this kind of coil failure. A good test with the noid light is to first try one injector and if no pulsing, then unplug the remainder of the injectors on that bank and try it again. If you get pulses, then you have one or more defective injector coils.

 

check fuel pressure on rail, first, if no, check fuse, then fuel relay, also listen for fuel pump start up with to on..then check fuses, INJECTOR

 

Is the 4 pin connector under distributor, connected and clean and tight ?

 

it has good fuel pressure... I'm curious why before it has bumped like its going to try and start but after that it just cranks and no hits

 

It would be appreciated if you could tell me what exactly tells the ECM it's time to fire the injectors

 

First off- is check engine light on with the key on? If not check fusable links by the battery they provide 12 volts DC to orange wire at ECM.
Another issue could be the VATS signal to the ECM. My vats module was bad but would allow the car to crank - just not sending proper signal to ECM to tell it to pulse injectors.
It would seem like it was trying to fire but then nothing. Made the 50hz signal generator - problem solved (for me).
I had both of those issues.

 

Reference signal from distributor, goes through the 4 pin connector I mentioned.

 

Ok i tried the light and got nothing... yes the check engine light is on but it stays on after all the others go off.. from sounds of it my ECM isn't getting signal from distributor or the vat is messed up .. I'm trying to find someone with a scanner for a reasonable price to see if they could tell me why the check engine stays on... Everything you all have told me has been helpful hopefully with these last few things i can get it running

 

Is this a new problem, or did you buy it with this problem ?
Have you tried to retrieve trouble codes from the ECM ?

http://members.shaw.ca/corvette86/No...it%20Check.pdf

http://members.shaw.ca/corvette86/En...ButWontRun.pdf

http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf

 

sorry i have been gone.... the service engine light has been on since i built it not sure if it was on when i bought from person it wasn't running at the time i don't figure it was... but i replaced ign module and it still doesn't give signal

 

thanks for the pdf files this should be a big help