I found out why our cam sensor has lower voltage on the Pink wire than everything else.

Fuse 5 / Pink wire out of it feeds the Cam position sensor in the distributor along with the Mass Air Flow sensor, EGR valve, Evap canister purge valve, Evap vent solenoid.

Fuse 10 pink wire out feeds the Crank sensor, Injectors, and Ignition module.


I bet the Cam position sensor voltage is lower because Fuse 5 is feeding lots of stuff prior to the engine running. Fuse 10's Pink wire isn't using power as the injectors/ignition are waiting to pulse. Just my theory on that.


I still haven't figured out why mine's only chugging/not getting enough fuel to fully idle without the starter.

 

heres what i know from using the scan tool....

the cam sensor will not cause a no start situation on our blazers. you can test the pulse signal pretty easily with a voltmeter and a helper to make sure its pulsing.
the tools diagnostics run thru check for spark, verify fuel at rail, check crank sensor, tps volts, check coil/ icm and trigger pulses then points at pcm.

theres a gray area in checking the trigger pulses and pointing at the coil so thats what im going back through tonight.

the mechanic that loaned me the scan tool said he worked on one almost identical to mine a while back and it ate his lunch, after a week or so of chasing wires and diagnosing he put a new distributor in it and it ran good enough to make the customer happy so he called it good.

started at battery voltage....
12.46 key off
12.31 key on

at fuse fanel key on
#5 12.06
#9 11.87
#10 9.96

at ICM
11.10 circuit A

at coil
11.00 (pink wire)

at injector harness (unplugged)
(white wire) 11.00

All the grounds were reading right at 12.50

checked for spark at plugs 5&6 both showed good spark.....
Installed new msd coil anyways, same results
tried 2 different ICM's... same results
swapped out pcm this morn, still no start... swapped back tonight, same thing.

just NO injector pulse but will attempt to start with a shot of starter fluid or carb cleaner. (do get code 1351 after using the starter fluid)

this thing seriously makes no sense and by looking at it on paper there is no reason it shouldnt run!

 

Maybe try cutting the ground wire to the ICM and running it to a new ground...maybe yours will start chugging like mine! LOL....atleast I started getting injector pulses with that crazy wiring try.

 

definitely worth a try at this point.

hey are your numbers similar to mine or farther off?

 

Fuse 10 only 9.96 volts? That feeds your ICM hot wire, coil hot wire, injector hot wires and you have 11 volts there?

Something doesn't compute.

I read this one post where somebody said if your ignition switch is bad....try turning your key when you crank it ever so gently until it barely reaches the point to engage the starter. If you notice your injectors opened up and it almost started....bad ignition switch. That post saved me lots of time and money narrowing things down.

I can't give you my values until tomorrow. I left the hood open with the harness apart/ PCM connectors out and it RAINED while I was out today. Gonna have to dry my PCM, plugs, and everything before I plug my battery back in. Gotta get some sleep now.

I'm at the other side of the planet than you...hence the time difference as well. I'll get you my voltages tomorrow.

 

i completely agree- it does not compute! but the meter hasnt lied to me yet! LOL

i will look into the ignition switch thing, but who knows! Hey I think you were on to something with the ignition switch... the switch side itself looks good but on the harness side it appears that at some point someone may have added and deleted a remote starter. at any rate, when it was deleted wires were were snipped, and the thick yellow one has 2 splices that are way longer than needed and they only twisted the wires together and taped them.
going to fix that shortly.... and get the battery charger back on it.

tried to put charger on it overnight. got it hooked up and plugged in and just closed hood on top of charger..... it appears a cat got in there, shredded my hood insulation and unhooked the charger (hope it got the shock of its life).

sorry bout the hood and rain.... been there bud!

 

got the mess under the dash cleaned up and got out the meter again.

Batt volts 12.35

at fuse panel (key on)
#5 11.63
#9 11.53
#10 9.65

got sidetracked by step son and forgot to plug fuses back in and started checking volts under hood and found......

cam sensor plug
wire C.. 0 volts

ICM wire A...2.10

Injector plug white wire....2.06

coil pink wire 11.58

plugged fuses back in and found.....

cam sensor
wire C... 10.83

ICM wire A... 11.06

Injector plug white wire 10.84

and the big stumper
COIL pink wire..... 11.09


I guess its time to find a wiring diagram I can read and tear the harness apart.

 

Could it be your engine block is grounded well but your cab/body isn't?

That would explain it. I had the car jumpered to the blazer to charge the battery up. I checked the fuse block, key on is 13-14 volts across the fuses. I created many new ground cables and grounded frame/block/body/battery all together.

 

went out to try that and my jumper cables are missing.

total shot in the dark here..... i noticed it wont even try to crank in neutral, ya dont suppose the neutral safety switch is causing this whole mess?????.... after finding a ground dist chart andprinting it so i can read it i see that the neutral safety switch is grounded on the back of the head with half the stuff not working.

got some printouts, off to see if i can either find something worthwhile or make some new grounds.

 

Any update on your wiring gremlins?

I gave up on ours. Already spent $3k in parts and replaced just about everything., wife says no more. Time forit to get junked. I did finally get minimal injector pulses and it would almost get enough fuel to start. But not enough. There's a gremlin somewhere in the harness....he beat me.

No more GM products for this family. Hope you got yours figured out.