1996 GMC 3500 SAVANA Van 5.7L Vortec Auto Trans 2WD. Crank, No Start, No Spark

Subject: 1996 GMC 3500 SAVANA Van 5.7L Vortec Auto Trans 2WDComments / Questions: Crank, No Start.  No Spark
With key on: MAF 12V
CKP Sensor 12V
Oil Press. Sensor 12V
Cam Pos Sensor 12V
Ign Control Module 12V
Coil 12V
EVAP 12V
EGR 5 wires, one had 12V and one had 5V
TPS 5V
Intake Air 5V
H2O Temp 5V
Intake Manifold Press Sensor 5V

White connector at ECM #27 Grey wire = 5V Ref. back pin actual = 12V
#17 Black with White Stripe, System Ground, Not open between connector and Battery NEG.
#18 Yellow with White Stripe, Ground, Not open between connector and Battery NEG.

Does this mean there is a bad ECM ground and or 12V battery intrusion somewhere?
I removed ECM, opened and inspected. No corrosion or bent pins. Van rust free.

Noticed Ignition voltage 1 low when cranking on MATCO Determinator Scan Tool.
Can see cranking RPM on scan tool.
Can see TPS activity on scan tool.
Can see test light flicker at Ign Control Mod and at Coil signal wire.

Battery grounds at body, block and chassis are good.
Ground on back of right cyl head good.

Van sat up for a couple years with no battery. No stored codes.
During trouble shooting, generated code P1351 Ignition control voltage high.

I have noticed spark out of coil wire come and go on two different occasions. No spark now.

No security, No chip key.

Ignition switch/harness new. I broke old one when inspecting plastic tumbler and contacts in switch.
I installed new distributor gear due to wear. Concerned about cam crank correlation.

Verified bad fuel pump. Installed and verified new pump and 65psi fuel pressure at return valve. Purged old fuel.

I have been watching your videos, and appreciate your teaching and finding root cause based on principles.

I need better understanding of 5V reference. Is there a step down transformer in the ECM, converting 12V bat voltage to 5V for sensors?

Thanks in advance,
Mitch

Your reading of 12 volts at the VCM Connector 3 terminal #27 does not jive with the 5 volts you said you got at the MAP and EGR. Are you sure you were on the gray wire at the VCM?

i.imgur.com/bRniQ3O.png

 

Noticed Ignition voltage 1 low when cranking on MATCO Determinator Scan Tool.

Do a voltage drop test on this Pink wire referenced to B+, while cranking at connector 1 of the VCM pin 4.

Can see test light flicker at Ign Control Mod and at Coil signal wire.

I have noticed spark out of coil wire come and go on two different occasions. No spark now.

Do you still have signal to ICM on the white wire, while it's a no spark? If you do, how's power and ground?
 

Mitch,
jreardon has you pointed in the right direction. To state the obvious, you have to have constant spark to get the engine running.
Start at the easiest point. The coil and work your way back along the signal path. No spark on the coil wire, move to the coil. Re check the pink wire for 12v then check the white black wire for a pulse signal. You need a scope but a test light will make due. Your test light should pulse, if not move to the ICM. Again check the pink wire at the ICM for 12v and a pulse signal on the W/B wire. If no pulse move to the White wire and check for pulse. Then to the VCM and again check the white wire for a pulse.
If no pulse from the VCM move to the crank, cam and knock sensor. The pink wire is again the power source for the cam and crank. The yellow is crank sig and the BR/WT is the cam sig.
You may know all this but assuming makes diagnosing harder. If you follow a path from your testing you're more likely to find the problem without throwing parts at it.
Let us know your progress. We all want your van running.

With a volt meter at C1 pin 4, (pink wire), and another volt meter at pink wire at coil connector. With key on there is 12 volts at each meter. While cranking, voltage drops to 5 at both meters. Butt connected a new 14 ga. wire at C1 pin 4 wire and at coil connector. Same result. Why is the ECM going from 12 volts to 5 volts while cranking?

Test light does flicker at ICM and coil while cranking.

wrote:

Why is the ECM going from 12 volts to 5 volts while cranking?

What's battery voltage while cranking? It should be about 9-10v on a healthy battery.

 

Battery voltage is good. I have kept charger on. Battery voltage also good at fuse block.

THe meter reads difference in potential. So if you place one lead (doesn't matter which end) on B+ and another lead on the pink wire (yes, another B+), crank it over, and you have something low (zero being perfect which doesn't exist), like 100 mV or .1V, that's a good wire (ignore the negative sign).

What do you get?

Meter on mV, one lead at battery positive post, the other lead at Blue C1 connector at ECM pin 4 wire. With key off meter reads OL. While cranking meter reads OL

Put meter on highest scale.

Meter on mV, one lead at battery positive post, the other lead at Blue C1 connector at ECM pin 4 wire. With key off meter reads 11.4. With key on meter reads .85. While cranking meter reads flashes between OL and 3.4 ish.

Put meter in volts DC, not mV. Your meter's saying OL because the value it's reporting is probably much higher.

Meter on Volts DC, one lead at battery positive post, the other lead at Blue C1 connector at ECM pin 4 wire. With key off meter reads 11.4. With key on meter reads .85. While cranking meter flashes between OL and 3.4 ish.

I apologize, I copied and pasted and did not edit accurately. I need to improve my electrical knowledge. Thank you very much for working with me.

Okay, somewhere along this wire, or at a splice or connector there may be some corrosion or unwanted resistance. The test you did tells you you're losing 3.4 volts which is bad. Time to split the diagram in half and retest at a location you can easily get to, which is... I don't know where, lol.

Are your battery cables on tight? Put your meter on battery post, and other meter on the clamp that's on that post and redo test.

Those pink wires power all the sensors. Could he just unplug one at a time and when voltage jumps to 11.4 he found the resistance?

Battery connections are tight.  Removed and inspected cable from battery to fuse block by removing from plastic cover.  No corrosion,  eye connectors look good.  
There are 5 connectors at the ECM:  white, black, red, blue and a small two wire connector.  
Looking at this info.: { troubleshootmyvehicle.com/gm/4.3L-5.0L-5...uts-1996-1997-page-3 }
C3 Grey (Is Grey equal to my White??) connector pin #21, orange wire is 12V battery feed.  Is this wire feeding 12V from the fuse block into the ECM?

wrote:

Those pink wires power all the sensors. Could he just unplug one at a time and when voltage jumps to 11.4 he found the resistance?

Mitch said Ignition voltage 1 low. That's pin 4 of C1. Mitch says he's getting 5 volts there. He compared this voltage to the voltage at B+ and he's reporting 3.4 volts of voltage difference during cranking. Mitch, just to be clear, the meter said 3.4 VOLTS right?