no injector pulse

Hello everybody i have a 1994 Caprice with the 4.3 V-8. I pulled it in the shop to check for a tranny leak and now it will not start. It spins over fine theft light goes off i have fire
but i have no injector pulse what could it be it was running fine when i pulled it in the shop now nothing. Any help would be great thank you in advance

Make sure the fuel pump is working. When these cars don't start and there's no code it usually means the pump is dying/dead

It was 11 pounds shy so i installed new pump, filter, screen and harness now pressure is right but still will not flash noid light

Have you checked for fuel flow at the fuel rail? Not pressure but actual "hose in a bucket" flow?

If you have good flow and good pressure then you can rule out fuel as the culprit.

Are you sure you have spark at the plugs?

If you rule out spark along with fuel then the issue is electrical.

Brad, he already said he is not getting power to the injectors.

GasTT wrote:

Brad, he already said he is not getting power to the injectors.

Always start with cheap and easy. Fixed a completely dead car once with nothing more than a fuel filter

If it's no signal at the injectors (all then there's something pinched/cut in the wiring harness or there's something screwy in the pcm

check fuses #6 + #9

fuses are all good have power to the injector but no pulse signal have fuel getting to the injectors have fire at the plug changed plugs just in case same problem it does not pulse the fuel injector

I would swap in a known good PCM just to rule it out before you throw more parts at it. Where are you located? I have a good working L99 PCM.

I live in Camden Tennessee pretty good little ways away lol. What kicks my butt is the fact i drove the car in the shop shut it off and then have nothing.

Did you check the resistance of each injector?
They should all read about the same (I dont know the ohms)
A shorted one can cause problems

Possibly 14 ohms... Give me a little time. I go to U.T.I. and I am actually taking the fuel and ignition portion of the training. We use the Modis and various scan tools. I can get some info from the instructor if I can get exact details based on symptoms. Its a shot...let me know if I can help!

car has given no problems at all has 112,000 miles on it i had a small tranny leak and pulled it in the shop to check it out and it hasnt started since. i checked fuel pressure it was 11 pounds low so i changed the fuel pump, filter, screen and harness now i have the right fuel pressure but still wouldnt crank. So i then checked the opti for signal which i have i have spark at the plug but no injector pulse the injectors all check around the same ohms all the fuses are good have fire going to the injector but no pulse signal. I am trying to figure out where the pulse signal starts from i hate to just start throwing parts on because that gets expensive fast. I am stuck on the computer but hate to buy one and that not be it because there is no returns on electrical parts.

I think the computer grounds the voltage for pulse.
Are the grounds ok? Wish I knew more specifics.
Could be a harness thing, look for any part of the harness that was disturbed while addressing your tranny leak?
I hate to send you elsewhere but maybe on ISSF you can find a local guy to buy computer
You should be able to get a computer for $50-80 and then you have a spare

sdstick wrote:

I think the computer grounds the voltage for pulse.
Are the grounds ok? Wish I knew more specifics.
Could be a harness thing, look for any part of the harness that was disturbed while addressing your tranny leak?
I hate to send you elsewhere but maybe on ISSF you can find a local guy to buy computer
You should be able to get a computer for $50-80 and then you have a spare

Going rate on ISSF is about $65 shipped for an OBD1 PCM...well worth it to have a spare. I'd offer one to you but I just sold all mine to one of the PCM tuner guys

Doug

I have a working '94 L99 PCM that came from my car I could sell to you via pay pal and ship it out to you. If you decide to go that route.

i didnt check anything on the car i pulled it in the shop shut it off and let it cool down went back to start it up and see if i could find the leak and it wouldnt start and now im where im at. Thank everyone for the help i guess im going to buy a computer and go from there. I'll let yall know if it works.

I just called and priced a new computer not a bad price but they said i have to take it to a dealer to have it programmed is that the case or can you just plug it up and go they said i would have to have a used one flashed to the car also

sdstick what all specs you need i can tell you everything i have checked and what i found on them

You won't need to get it programmed if it came from the same year and had the same engine. The computer I have came from the exact same year make model and engine option as your car. 1994 Chevrolet Caprice with 4.3L L99 engine. I can do $65 shipped to your door, I've had this thing sitting around for over a year and I have no use for it.

sschmelter wrote:

sdstick what all specs you need i can tell you everything i have checked and what i found on them

I was saying I wish I had more specifcs, meaning, wish I had more to tell you to check.
You can google this problem & find other forums where they trouble shoot this type of issue.
I dont want to just retype that like I know what I'm talking about.
I'd buy GASTT PCM & keep my fingers crossed its all triggered in the PCM
I can back him as a stand up guy, but anywhere else you mentioned...not so much
I never trust a parts store because every dope in the world returns shyt to them saying it was fine & the next guy gets stuck with it.

Google stuff:
there are some opti, ICM and injector DTC's that disable the injectors and fuel pump (after start) but do not illuminate the SES (CEL, MIL whatever you call it). You would need a scan to verify this. Are the fans running when you try to start it (they should not be), if so you could have a DTC causing that. Another thing to verify is the two tan ground wires on the ground stud in the front of the left (pass) head are installed . They feed ground to the PCM injector drivers. There should be a black wire to ICM/Coil, a braded wire to the frame and the two tan wires to the PCM on that stud. Also check that you have +12V on the both wires to each injector with key on-engine off-not cranking, that verifies the fuses and harness is providing power to injectors.
The injectors get +12 IGN on to the pink wire in each injector. And the other wire (different color for each injector) is driven to near 0V by the PCM to pick the injector. When the PCM is not picking the injector the 0V wire is technically open and the +12 flows through the injector coil to the wire to the PCM. Therefore you should have +12 V on both wires of each Injector with key on , not cranking condition. NOTE..The injector connector must be connected to the injector when you test this, also you s/b using a high impedance digital meter for testing PCM circuits. Can you verify this ?? If you had +12 on pink and 0V on non pink with the connector on the injector, then the injector would be constantly picked.

have full 12 volts to the injector not receiving ground signal from computer. I am pretty sure it is the computer now since i have checked all the wires grounds are all intact and making good connection. I have a buddy that has a caprice with the same set up so i am going to see if he will come bye and let me try the computer now that i know it doesnt have to be flashed by the factory. Thank you for all the help

Post back when its confirmed fixed
Good Luck

When you turn the key, does a security light flash? Some of the theft systems disable injectors and such.

MASShole9C1 wrote:

When you turn the key, does a security light flash? Some of the theft systems disable injectors and such.

I thought vats killed the ignition part of the system. It would deffinetly solve your problem if the vats controls the fuel system. I'm sure someone can shine a light on that angle for us.

My thought is the pcm isn't getting a good crank signal to know which cylinder to fire. But that would also disable the ignition at the plugs too

bammax wrote:

MASShole9C1 wrote:

When you turn the key, does a security light flash? Some of the theft systems disable injectors and such.

I thought vats killed the ignition part of the system. It would deffinetly solve your problem if the vats controls the fuel system. I'm sure someone can shine a light on that angle for us.

My thought is the pcm isn't getting a good crank signal to know which cylinder to fire. But that would also disable the ignition at the plugs too

That was my first thought but he said the light goes out. The body computer tells the PCM to turn the injectors on so it defiantly sounded like a passkey problem.

Brad can tell him how to remove the light
Actually we have a pretty good passkey trouble shoot thread

the pass key light does go out still waiting for my buddy to bring his car by so i can try the computer but as of now still no luck

no luck with the computer so im lost

wiring dia.
http://www.goldsswagon.com/diagrams/wiringindex.htm