Spark, Compression, fuel pressure...NO INJECTOR PULSE?

[bansheerider84]

My 94 firebird formula is really getting to me. I just did a water pump, opti, timing chain. Car was running fine. One morning in Indiana it got down to 14 degrees. It was hard to start but fired up. Drove home from work and parked it. When I went to start it again it just turns over. No unusual sounds when its cranking. I checked the compression and its good, fuel pressure read 42-44psi on prime. I hit it up with some starting fluid and it starts to run so its sparking. Threw a noid light on all the injectors and nothing. Double checked my bonny and the light is working

Is it possible my PCM just quit? I'm not a master mechanic by and means but that just seems really unlikely to me. I was also thinking the optispark could have somehow went bad again but as long as the optical disc is there shouldnt the injectors still pulse? Like always I assume there is something I am missing or overlooking..Any suggestions would be appreciated
!!!

[steveo]

before going any further, you need to check for 12 volt ignition switched power at the pink wires on the injector plugs (ground to chassis) with the car not running.

if you dont have that 12 volts, it's not the ecm or opti you're dealing with. could be injector fuses, ignition switch or wiring, or the 'big pink splices of doom' in your engine wiring harness

[steveo]

and yes, if you lost opti pulses, you'd lose spark and fuel -- but it's weird for this to happen right after swapping an opti. it's likely the opti.

if you have injector power, and the injectors are not pulsing at all; there's not much else it could be, and i question your shaky 'i used starter fluid' proof of spark too

[bansheerider84]

I steve-o I pulled the # 3 plug and checked for spark, since it was easy to get to. I hit it up with a little starting fluid just to see if it would hit and it did. I ponied up for the AC delco opti and it literally has 200 miles on it. The opti went on with ease, I didnt force it or anything like that. So just so I am clear the opti controls the injector pulse? and is likely the problem. Really not looking forward to taking that dang thing apart again. I didnt ohm all my grounds but they all looked good from what I could see in my garage.

[steveo]

Originally Posted by bansheerider84

So just so I am clear the opti controls the injector pulse? and is likely the problem..

really, all that has to happen for the injectors to fire:

- power on the pink wire
- opti sending pulse to the ecm
- ecm pulsing the ground wire and the injector fires

double check the harness to the opti, make sure it's plugged in all the way

man i had a brand new ac delco opti die before it even left the jackstands in my garage. it happens..

have you scanned it to see if there's any high res pulse failure codes stored?

[Project96]

FI systems need to know where the crank is in order to fire the injectors. If it doesn't know then it wont send the ground pulse to the injectors. The opti is where the ECM gets that signal. Has it fired since replacing the timing chain? Mine would shoot a flame out of the TB about a foot or so because the splined pin in the center of the cam gear was installed incorrectly. So the ECM was sending the signal at the wrong time. Fixed that & all was ok in my LT1 world.

[bansheerider84]

Yea the car ran for 200 miles and some change. Steve-o i shouldn't be getting spark with bad opti right? I checked and I'm getting spark on all plugs. Been drinking some beers and my friend has my multi meter. Ill check for 12vlts at injector harness tomorrow.

[cocobolo95]

Nobody has asked if the security light is on. That will stop the injector pulses also. tdm
(theft deterrent module) sends a 50 hertz signal to pcm, when all is well with security system. THe 50 hertz signal tells the pcm to enable the fuel injectors. From the factory, security also disabled the starter, but given the age of the car and the many owners it has probably had, that feature could have been bypassed.

Since your car will run with starter fluid, it is getting spark. However, you should scan for codes. If you have the silent codes dtc 16, 41, & 42, all of those disable the fuel injectors and don't light the check engine light.

Does your security light come on for several seconds when you turn ign sw to on position, then go out. That means security system is well.

To test if fuel enable signal is missing, you will need a signal generator that can feed the 50 hertz signal to pcm connector A25
dark blue wire. Since most people don't have a signal generator, I would suggest a 50 hertz bypass module from baker electronix.
www.bakerelectronix.com/products_vats/
$35 + shipping

[bansheerider84]

Just thought id update the thread and seek a little more advice. I messed with the car a little today and I have 12 volts at the injectors but they are not pulsing. So even though I just replaced it with a AC delco..I am assuming the opti? Whats crazy, the car ran when it was parked..then nothing