need help on my first LS conversion,04 LQ9 in an 86 K5, no start

[vortecyota]

Thanks for the replys. Just finished checking out crank and cam sensor wiring. No shorts to ground or each other but mysteriously I now have 11.6 or so volts to crank and cam sensors. I'm going to put pcm connector back together and try it again before I buy new sensors. Will be tomorrow before I can get back to it.

I modified an 04 escalade harness per the "pinout" sticky, btw, thanks RedHeartBeat. PCM is 12576106 with Hwd. No. 12570558. I'm using this one because the only trans I had was a 700r4 and wanted to use dbc instead of dbw.

If crank sensor was bad, I wouldn't see rpm on scan tool, right?

Thanks for your help

That's correct, if the ckp signal is missing, weather it be due to faulty sensor or wiring, you will see no rpm during cranking while monitoring an engine speed pid. I would certainly check that before buying anything if you're able. Good luck, ill keep checking in.

[stevebbc]

Tried it again today after putting connector and old sensor back in. Still no start. Ocassional firing with valves still open, back thru throttle body.

So what is sensor supply voltage supposed to be. All the schematics I see of the crank and cam sensor say 12v ref.

Going to try new crank and cam sensor unless somebody's got another idea.

thanks

[RedHeartbeat]

Try a noid light on the fuel injectors and see if they're firing. They could be stuck if the engine sat any length of time in the bone yard.

[stevebbc]

I got a loaner set of lights today from AutoZone but none of them are the right size. I'll try Advance or Oreilly's.

[stevebbc]

Just another piece of info, I have pulled off injector connectors and put voltage to 4 or 5 of them and all have the solenoid clicking if I just quickly touch the negative. So I think injectors are good and not sticking. I've built 7 or 8 motors and tuned a bunch more. (old school)This is a classic timing issue. Backfiring thru the intake and starter is struggling to turn it over.

Thanks

[vortecyota]

Just another piece of info, I have pulled off injector connectors and put voltage to 4 or 5 of them and all have the solenoid clicking if I just quickly touch the negative. So I think injectors are good and not sticking. I've built 7 or 8 motors and tuned a bunch more. (old school)This is a classic timing issue. Backfiring thru the intake and starter is struggling to turn it over.

Thanks

Hmmmm. Strange. You can use any noid light. Just make a couple small jumper wires to attach the pins on the light to the pins in the inj connector. If you think its a timing issue, there would have to be coil control wires crossed up. Im really curious now. I had a cmp connector pinned wrong once and it took forever to start the engine, all the while backfiring. That sounds very similar to your troubles. I doubt you have a ckp problem because you have some spark and fuel. Cmp on the other hand is looking more and more suspect. Keep at it. It'll be worth it.

[stevebbc]

Just put in new crank sensor and its very close to firing up. What is a crank sensor learn procedure? Is it necessary for a start? or does it just improve performance?

thanks guys!

[RedHeartbeat]

did you check and ohm out the wires to the crank sensor behind the starter? Flex the wires around by the connector down there, I've seen them break internally and work intermittently. Other than that it's pretty much VATS keeping things from going.

[n-guerra]

hey steve are the shematics u have are from like gm work shop manual ? normally all sensors run on a 5 volt ref , but if u say u r shematic says 12v and on ur previous thread u said u had no voltage on the pwr for the crank sensor and then u did load test that circuit with a fog lamp bulb u could have high resistance, have u already ckd for fuel pressure or spark are all the plugs wet or only 4and 6 did u ck with noide light if injector signal ill try and get a shematic from work tomorrow and see if it says 12v like urs on crank sensor

[stevebbc]

n-guerra, I replaced crank and cam sensor, now have 12v at sensors. Schematics are from links on this site and they are complete GM schematics for 03 Silverado 3500, in color even. I'm using this in conjunction with chart on LT1 Swap site on what wires to remove for a harness to run the motor only. Now could the positive 12v be knocked down to 5 by a -5v low ref out of the pcm? If so, then maybe u r on to something. Maybe this feature in the pcm is not working. I still have the 04 Escalade pcm with factory programming. Would it hurt anything to connect this one just to see if it would run it for a few seconds. I know the vats would turn it off.

I have fire all the way round now and noid is lighting on all injectors. Took fuel rail and injectors off last nite and tapped them with 12v. All were spraying plenty of fuel that was still in the rails.

Vortecyota - I'm in eastern N. Carolina. at least for now, if my wife doesn't kick me out