no power to injectors... please help!! after 4.3l - 350 swap

[wally91vhevrolet]

i just recently did a 4.3 - 350 motor swap. I have a computer with the chips for the v8. I cranked the truck about 5 times and it ran fine. Then it just wouldn't crank. I've checked many things for this problem. I tested the connectors on the injectors with a test light and wasn't getting any pulse when the motor was turning over. Also, i checked the injector fuse under the dash for power. Wasn't reading power at all in the off, on, or crank position. I checked a mini fuse by the fuel pump relay under the hood. Also replaced all 3 relays behind the dash. My assumption is the computer is reading something that is preventing the injectors from pumping fuel. I'm not getting a service engine soon light. But i also can not get a diagnostics to work at all on the cpu when i ground out the test terminal. I tested the orange wires on the cpu on each connector and they both have power. I'm just completely confused. I've seen someone had the same problem online but i cant see what happened because you have to pay to see the "answer" so someone please help me out. I just don't understand why the motor ran fine and all of a sudden wouldn't start. Oh, and it is gettin spark to the plugs i also tested that. Please help.

[wally91vhevrolet]

i bought a dist that im going to put in... doubt it will fix this problem... but the dist in the 350 is the original and is pretty rusty and worn out looking. But i did figure out that i cant get a service engine soon light to come on even when i run a test for trouble codes. It doesn't come on when i turn the key on like its suposed to. I checked and the ECM is getting power. Someone please help me out! I'm stuck. I've checked every fuse there is and wires. I guess ill put in the new dist and check some more wires. All of this just started out of no where after i put the 350 in it cranked 5 times and now it won't crank or spray fuel. Assuming its an ECM problem. But i did put a known working ECM in my truck and still no SES light or any spray from the injectors. So please, someone, is there a hidden fuse or anything in these trucks? Just please help

[wally91vhevrolet]

does no one have any ideas? heres what else i've found, sounds like a short somewhere to me but tell me what you think. I put in the new dist yesterday (my old one was trash, falling appart and everything). I been testing circuits like crazy with my test light (its all i have). I have power to the cpu. I have a ground from the cpu. One thing that has confused the hell out of me is if the cpu is plugged in, the key is in the on position, i am reading power from the casing of the CPU to ground with the CPU being the + power. Now, is that a short? or is this normal? Maybe a stupid question but i've seen some weird things in my day. Also checked NO wires are touching the cpu when i did this. Also unhooked one connector and checked, it still happens. Unplugged that one and plugged in the other, and it still does it. I tested it with my old 4.3L cpu AND my friends CPU and it does the same thing so it has to be in the wiring if this is not normal. I'm also noticing power on EACH side of the injector connectors to ground. I know this is not normal. So can anyone please tell me any ideas on where to start checking my wires for maybe pinched or burnt wires? I've looked a little but not real good. Guess ill do that tonight. Yall tell me what you think.

[wally91vhevrolet]

ah and if anyone has a GOOD wiring diagram for these trucks could you send one to me? i have a haynes manual and its missing so much shit and a lot of stuff is not right. Thanks

[777stickman]

Well I've been looking at your post along with about 40 others and still I'm (we) waiting for you to mention the year of your truck, model, etc along with the year and model, etc the 5.7 came out of.

Another issue I have is your reference to "cranking". "Cranking" is refered to as "engine cranks (turns over) but won't start". Please clarify that for us.

[wally91vhevrolet]

sorry its a 91... i figured the problem out it has a short somewhere... anyway ill keep yall posted

[jeremylkelleysr]

wally, really interested whether or not you figured out the problem. i have n 89 chevy 2500 with the 350 tbi that is doing the same thing. i have replaced the timing set, distributor, ignition module, pick up coil, ignition coil, cap, button, plugs, wires, fuel filter, ecm, ignition switch, and even rebuilt the uel pressure regulator. i still have the same thing, no service engine light, my injectors are not spraying even though there is plenty of fuel getting to the throttle body. we have dumped fuel down the throttle body and the truck will fire right up for a brief moment until that fuel burns off. any suggestion you could offer would be greaatly appreciated because if i don't figure this out soon, i am going to lose my job because this is my only transportation.

[wally91vhevrolet]

I never really figured out the exact cause, but i did ground my computer casing. And it made it work, havn't had any problems and its been about 2 months now. Don't know if the CPU is supposed to be grounded, but if there is a short it must be filtering it out and letting it work. Give it a try and let me know if it worked for you too.

[j cAT]

Originally Posted by wally91vhevrolet

I never really figured out the exact cause, but i did ground my computer casing. And it made it work, havn't had any problems and its been about 2 months now. Don't know if the CPU is supposed to be grounded, but if there is a short it must be filtering it out and letting it work. Give it a try and let me know if it worked for you too.

1991 vehicle will have rusted corroded ground connections,,,,your ground problem indicatates to me,,,, you must check/remove /clean/all....

[wally91vhevrolet]

thats what i was told before and i cleaned all mine and replaced them also but still had no luck, with a computer casing grounded the truck works fine. swapping to a carb soon anyway after i build my motor