Thread: Help...not getting fire

Fuel pump would actually have a different ground IIRC. I'd like to see you test for power at the inj clip for one of them. Then you'd be going back to the fuel inj fuse if there isn't 12+ present. Which may lead you in different directions. But I'd bet you are getting power there, which leads us back to the pcm not giving the toggle for the ground. Which might lead us to the pcm not having the connector fully seated or the connectors being on the wrong sides of the pcm. Which isn't easy to do as they are tied and taped up in the way they go.

The computer is usually sitting in the airbox. Open it up and you'll see two large connectors that should be held to it by 7mm bolts. One in each connector. Those should be snug. The clear connector attaches to the pcm where it says clear and blue on the blue side. If you remove the connectors, you'll see the wording on the pcm. While those are removed, look for any bent pins on the pcm.

I would like to reiterate what Bill said:

All of your injectors are supplied with 12 volts positive (PCM controls switching via ground) with the key "ON". For each 2 wire injector, one wire is hot with key on and the other is a switched ground from PCM. Check if there is +12 volts at the injectors with the key in the "ON" position.

If there is not 12 volts then check the injector fuse.

If the injectors are supplied with +12 volts then check if the PCM is actually commanding them:
This is simple - unplug any injector and hold the multi meter leads on the two wire conductors while cranking the engine. With the meter set on "Hz" you should see a frequency deflection of 2 or 3 Hz. This means that the PCM is switching the ground (on/off) 2 or 3 times per second.

If your not getting a signal from the PCM to command the injectors then I would check the PCM grounds and the crank sensor.

Edited:
At Idle the frequency should be around 11 or 12 Hz.
12*60=720 RPM

i just tested a injector wire on my friends truck today, i got the plug off the injector, and with the key on, and with a simple test light found solid power, on the one wire, with the tester grounded to the battery. when i had the truck running and had a paper clip stuck in each side of the plug. the clip for the tester on one side and the test prob on the other and it pulsed.

it should also pulse while cranking it.

Yea, I guess if it doesn't actually start the pulse should be very noticeable while just cranking.
Thanks for bringing this to my attention. Previous post has been edited.

i just learned that myself, as i never had to test injector wires before, i was googleing the code for my friends truck, found a link to some help forum, and if you read it you would have thought it was billboost helping this guy, it was good thread.

went to my friends house and just did the this test like a mere 6 hours ago lol

the paper clips pushed into the end of the plug was a awesome tip too, with out it you cant get a test prob to read or contact properly. my friend kept saying cant you just stab the wire, im like lets not f up the wires ok....

I use my Fluke 123 oscilliscope and a AC/DC current clamp. It's so easy; just put clamp on +12 volt injector wire. You don't even have to unplug the injector.

Most people don't have an oscilliscope laying around though.

Rico..you have a cooler toy.

Scott..next time skip the paperclip. Go straight to a 194 (side marker) light bulb. Straighten the leads on it and stuff that in there. Bet you didn't know your car/truck was carrying it's own test light did ya?

Knightmare - I'm not posting anything for you in this thread until you follow the suggestions. Til then, I'm fairly certain you don't want the car to run. The combined experience of Rico, Scott and myself.....it's a shame it's being wasted.

thats a good one bill, did not know that trick, just learned how to do the back yard test the night before, because i needed to test one.

and that injector is over a 100 locally, and the o2's for that truck are over 100 each, all ordered on line, 44 for a injector and 60 each for the o2's. i know what im doing next weekend lol

Also..FWIW GM typically supplies power to the injectors via ignition on. Then toggles the ground via the pcm.

Knight.. You can take a 194 (side marker) bulb. Bend the two tabs straight and push those into the injector clip. Have someone watch it closely and turn the key on from the fully off position. You shoudl see a quick couple of flashes. This would show you that the injector was priming the cylinder with startup fuel.

After you test...put the bulb back...lol Gotta keep it on hand for the next test time.

Damn crank sensor huh?

Glad it's running.

Bite my crank-----------------sensor. LOL