Gray Ghost 8991

Ok, I've dug around in the threads and found a few that were very useful but I feel like I may have a unique issue.

As of now what have is a 91 camaro TPI swaped RS. I'm using an after market harness to run the car and it WORKED great but of course I had to go mess with it. I was running a stock intake and injectors the car had no running issues at all I just droped in the new engine last year. Well after some research I decided to change intakes and go with the Holley stealth ram with a 58mm throttle body, fuel rail, 1.6 roller rockers and 30 lb injectors (522-308). I also had a tune setup for all the new parts. Well intake install was a breeze, but when I went to fire it up to set the rockers no start.

So long story short I have good spark, car will run on starter fluid not well but it'll run. Checked injector pulse with a noid light and it's a very weak pulse. So i started checking through the suggestions in other threads. I have 12v on the power side of the injector plug and I have a good ground on the other side of the plug (just used a test light ran from power to ground side of injector plug) and got a good bright light. I've ohmed the injector wires from the ecm They're Good, made sure the ground for ecm was solid it was, and i grounded the ecm case still no start.

I apologize for the long intro but I wanted to provide as much info as I could. Thanks in advance y'all I really appreciate this site !

DENN_SHAH

iTrader: (1)

the only time there should be a ground on the ECM side of the injector plug is when the ECM is commanding the injectors to fire.
with the ECM unplugged, check the ECM side of the injector connector to ground, it should be an open curcuit.
recheck all your grounds, battery to motor, battery to body, & body to motor.
did you try the noid light with all the injectors unplugged to see what it does?

Gray Ghost 8991

Ok I took care of the ground situation, I had jumper cables run from battery to the serp. Belt bracket, body to battery and, block to body. And I did check the injector pulse with all the other injector plugs taken off, but I didn't have all the jumper cables hooked up I will test it that way tonight hopefully. I did the test vader suggested in this post.

www.thirdgen.org/forums/tpi/320141-weak-injector-pulse-possible.html

And results came out good

DENN_SHAH

iTrader: (1)

there is a GM test that can be done, i know its posted somewhere on this site but a search isn't turning it up.
i don't recall it listed in the thirdgen repair books, but it may be.
i know it is in repair books for the OBD1 DIS systems.

on one of the wires from the module in distributor to the ECM, using a test light you do an injector scratch test. with the key on what this will do is tell the ECM to fire the injectors.
with the test light hooked to battery positive & the 4 wire distributor disconnected you touch, i believe its the blue/white tracer wire with the test light. the ECM sees this as a signal from the distributor & should trigger the injectors once or twice per touch.

its been a very long time since i worked on cars for a living & been quite sometime since i posted regularly here, so the memory is a bit faded

GeneralDisorder

iTrader: (1)

Just went through this with a car that came in with a VATS 30Hz simulator wired in. Even though the simulator was working from what I could tell, it still threw a code 46 for VATS error. Thing is when I was checking injector pulse it was still pulsing the noid light very faintly! Should have checked codes first but a noid light check was quick and easy also - misleading though because I assumed that a VATS situation would create no injector pulse when in fact it still pulses but has a very high resistance on the control circuit.

I burned a non-VATS chip for it and immediately got normal injector pulse level on my noid light and the engine fired.

Gray Ghost 8991

Well I would check that out but I've got VATS completely deleted already. I apologize for not mentioning that in my original post

Gray Ghost 8991

Ok I performed that test and I did have injector pulse. I had a niod light hooked up, it lit up. And I heard the injectors click.

Also I thought I might have had a stroke of genius. I took out my new injectors and installed my old ones. Reason being I thought that maybe the pcm company didn't set up my system for high impedance injectors. The injectors clicked when I was cranking it but it still didn't fire up. I doubled checked my distributor setup and it was right. Also I ohmed out my my ECM ground wires all made my meter beep and it didn't show any resistance. Also I made extra sure I had ground so disconnected the ring terminal for my one harness ground and grounded it to the battery still no start. What else could I be missing ?

Vader

Just for reference, the original injectors would have been considered high-impedance as opposed to peak/hold injectors. If the replacement injectors are not also high-impedance (resistance around 12-18Ω) there may have been damage to the injector driver transistors in the ECM. If that were the case, a replacement ECM may be in your future.

What is puzzling is that you report the injectors clicking (operating) during cranking. That should have admitted fuel if the pressure is sufficient unless something is plugged (like injector inlet screens).

Gray Ghost 8991

I'll go back and double check the ohms on both and I'll post back tonight. I did ohm them out and I was getting around 16-17 on both but I wanna make sure. And yes it is puzzling that they're clicking but no start. I'll also check fuel pressure tonight and see what it is. I'm running an airtech fuel pump stock for a 1988 camaro iroc z. It's only been in a little over a year since I installed it but parts do fail. Anything else I should check ?

DENN_SHAH

iTrader: (1)

im a seasoned mechanic & for a few days some years back i was having a hard time with why my car wouldn't start. fuel pumps were coming on & sounded normal, had good fire & injectors were working. even pushing in on the sharder valve i got a nice squirt of fuel.
when i did dig out my pressure gage,.. & i do mean dig it out as it was in my tool box which was buried behind a bunch of other stuff, i found the problem right off. 20 pounds of pressure isn't enough to even get it to try to fire off, but it was enough to make me think the fuel pressure was ok.
my pumps were both just a few months old at the time.
you know what they say about the animal that has the first name of jack, right? thats what i was feeling like,..

Gray Ghost 8991

Ok just finished testing for the night
I ohmed my injectors
New
-13 ohms
Old
-17 ohms

Fuel pressure test
KOEO 65-70 PSI
During cranking it didn't change
Another thing i noticed when I was disconnecting my fuel filter to T in the pressure gauge the fuel looked a kinda murky and I just changed my filter two months ago. I also noticed the same thing when I swaped out my injectors to try the old ones. I run 93 octane and i always use BP gas. Could it have been water ? The car has been under a shelter the whole time I've been doing this.

Also I load tested the injectors I left them all hooked up, back probed the power side to volt meter, volt meter to ground. Key on I had battery voltage when cranking it dropped to nine volts. And I've had the battery on a trickle charge to keep it up too. What's next? Any ideas ?

DENN_SHAH

iTrader: (1)

murky fuel can't be a good thing. take a sample in a clean & dry plastic coke bottle & let it sit for a while. if there is water, it will settle out to the bottom.

9 volts cranking may very well be your problem. the computer basically shuts down at anything below about 9.6 volts.
if the battery was reading ok, then you got a voltage drop some where. start checking power side wiring & don't forget about the bulkhead connector.
not long after i swapped the TPI motor into my car i started having intermittent cranks ok with no start. ended up being a few things that added up, but mostly it was a bad ignition switch.

Gray Ghost 8991

Well guys I can't thank you enough for your help. But turns out it was something very simple and I'm really kicking myself now......i had my fuel lines hooked up wrong return was on the feed side and feed was on return side.......soon as I swaped the lines she fired right up. Lesson learned, READ THE DIRECTIONS and don't assume anything. Again I can't thank everyone enough.