97 5.7L Vortec engine was running fine until I let is sit for about a year. Now I'm getting crank but no start, no fuel @ rail and no spark (according to a shop I brought it to, which also tried a new distributor as it was previously throwing a p0340 camshaft position sensor error)

Main suspect thing is I'm getting 12v on ALL the crank position sensor wires (pink 12v, purple ground and yellow 5v reference) I get this whether the sensor is plugged in or not and whether key is on or not

Tried:
- Checked crank sensor wiring, connector and most of the main wiring harness for shorts, open connections, bad grounds etc.
- New ECM
- New battery from Costco
- Checked that ECM ground has continuity to battery neg. May try re-running a dedicated ECM ground to chassis (???)
- Tested fuel pump working
- New fuel filter
- New fuel pump relay
- Shop tried new distributor
- Checked voltage @ yellow reference signal wire while cranking engine. Voltage drops from 12v to hovering around 10v. Don't have a scope to test for wave/modulation.
- New crank position sensor....although it was from O'Reilly's so likely aftermarket. Maybe try a new one?
- Checked battery drain, getting about 100ma with key off
- Pulled fuses to try to find drain or source of the potential "short" (between pink and purple wire) ....only fuses that have an effect are the ENG and ECM fuses (obviously, because they cut off connection to the ECM)

Again, my main concern is the 12v AND ground continuity @ the crank sensor (even with sensor unplugged). I understand that some sensors use modulation and dump some voltage to ground, so perhaps those readings aren't a problem after all?

Should I try another new crank sensor? Check for a bad ground (if so,, any method to help narrow things down?) There's no ignition interlock on the vehicle and it always started find before, but is it possible that the ECM reset to factory default after sitting so long (it sat with a dead battery for many months) and now wants to see the immobilizer signal?

Any other ideas? I've been working on this a week and it's driving me absolutely insane! Thanks fellas!



Far left and right indicate where leads were placed. Voltage, continuity and resistance measured with key off, sensor plugged in although no real change for key on sensor unplugged

Battery draw with key off. Roughly 1 amp with key on.

New ECM that came out of a 97 Tahoe with all exact same numbers except BNHM instead of BNHP. Same symptoms with new ECM.

Checked the spider for shorts or corrosion

 

So with key to run,no fuel pump prime either?

 

Correct Only way to get fuel @ Schrader valve on rail is by applying 12v directly to the pump.

 

My thought is,it's before crank sensor,the problem,that is,loss of power

 

Crank sensor plugs directly into ECM. Again, voltage to sensor looks good, it's just (seemingly) on too many wires (unless this is some kind of modulating circuit) . Battery voltage is good I keep it charged between 12-13v. Again, this is just crazy, doesn't make any sense I feel like I'm missing something obvious or it's possible I got a bad crank sensor? Or both ECM's are bad or have the ignition immobilizer enabled somehow? (even though the original never had this feature, perhaps it was reset after sitting for months?)

 

I haven't checked one that way,just continuity,but, again,no pump prime,that's before CPS,no security on that truck?

 

From what I've read, if the ECM doesn't get a signal from the crank sensor it won't prime fuel or fire injectors. Yeah, no security, never was a problem before ...I just don't know if ECM's default to some "factory preset" after sitting for months with no power. That seems like a long shot though

 

I'm not sure,I believe the pump will still prime,but power is cut to spider?how about looking in book for power out of ignition switch,crank is purple,I think pink is "run"

 

Or power wire to icm,live on "run"

 

Have 12v to ICM and spider (I believe they're both on that pink wire which is same as crank sensor.. .hooked directly to same place).....but again, this also seems to be "shorted" to ground ....which doesn't seem possible without some electrical magic in the ECM (modulating/switching or whatever) ... I just don't know how this process works