ksousa

Solved. See post #9 below.

So I've been searching and reading a ton of posts about no spark / no start issues.
I've seen and tested everything that I've seen suggestions on so far.

Motor is a 2001 5.7
I've done a couple of 5.3's and this is my first 5.7

Symptoms: Engine cranks and cranks but will not fire.

1) ECM has been flashed by a trusted programmer for this swap.
2) I have fuel at the rails. Pump comes on for a few seconds then turns off unless I'm cranking and it runs while cranking.
3) I have 12V power at each of the coils with key on and during cranking.
4) I have ground at the coils. Continuity back to the negative battery.
5) I have 12V power at each of the injectors with key on and during cranking.
6) I have ground at the injectors. Continuity back to the negative battery. EDIT: I do not have ground at injectors. I'm assuming it's the PCM that pulses ground to fire as needed?
7) I see 159 RPM when cranking through OBD and my basic scanner.
8) Crank sensor seems to check out. With key on, probed the signal wire, turned engine over by hand and watched the signal wire alternate between 0 volts DC to 10 volts DC. The engine builder had a grey crank sensor in the engine (58X reluctor) but when I look inside the motor with my tiny camera, I see the twin reluctor wheels telling me it's 24X. I replaced the grey sensor with a black sensor.
9) Tried unplugging the cam sensor.
10) I've ordered a set of NOID lights to check pulsing. In the meantime, I have my timing light on the plug wires and do not see any fire going to the plugs while cranking. EDIT: First time using NOID lights, but plugged one into an injector. I get a pulse/light when I first engage the starter and again when I let off the starter. I had a few pulses while the starter was running but that was not the norm.
11) I inherited the wiring harness and PO had already thinned it out. I ran through my normal process of integrating into what they had done and it seemed to be done and identified correctly. The one odd thing is that I do NOT see the multiple grounds that I've seen before on 5.3s and that everyone says are so important. I don't even see where they would have been in the original harness. I have a robust ground from battery to head. Battery is in front of car. I have another robust ground from head to block. And per points 4 and 6 above, I'm seeing ground at both coils and injectors. Edit: I do have one of the large grounds at the rear of the heads connected.

Edit: I tried swapping out a recently flashed PCM and have the same symptoms.
Edit: I swapped out the crank sensor with a used OEM sensor. Also did the hand crank test and still see alternating 10V DC and 0V DC so I believe the crank sensor and wiring is fine. I also still see 170 RPM on OBD while cranking with starter.


Options that I see yet to prove would be a bad PCM or the missing grounds issue.

Any other thoughts from the experts?

thanks

Darth_V8r

iTrader: (4)

Moved to pcm section for more traction

mrvedit

What PCM/ECM are you using?
Curious about having to change the crank sensor, but if your scanner shows cranking RPM, it is sending a signal. Lets make sure it is a 24x PCM.
From your description I'm not concerned about the grounds assuming the engine block isn't full of rust.

ksousa

Serial number on the PCM is 09354896. Appears to be '99 and '00 so 24X yes?

Also see edit on NOID light test in my original post.

mrvedit

Yes, PCMs from those years are 24x.
Yes, the PCM grounds the injectors to fire them.
Glad you confirmed you have +12V to the injectors and coil during Cranking; some people custom wire the ignition switch wrong and miss that.

Currently I would suggest two things:
1. Use a spark plug test light to see if you are getting spark.
2. Consider installing a fuel line pressure gauge to ensure you have decent pressure.

If you confirm you have spark, and confirm the injectors are clicking either with your NOID light or with a stethoscope, try shooting some starter fluid into the open throttle blade. If the engine then fires and dies you know you don't have enough fuel pressure.

ksousa

Thanks for working with me on this.
I have tried the spark plug tester and we are not getting spark to the plugs.
I've just ordered a fitting so I can tap into the fuel rails and measure the pressure. Might be next week before I can test that. Would low fuel pressure prevent spark to the plugs?

mrvedit

Sorry that I missed that there is no spark; guess that is the title.
No, lack of fuel pressure would not prevent spark.
You mentioned some insistent injectors activity; this made me expect at least some spark.

Based on other recent threads here on similar/same topics, you might want to consider another crank sensor, getting a genuine AC Delco unit.

ksousa

So I have:
Tried starting fluid with no results. I am more and more convinced it's electrical as I have no spark going to the plugs. I still need to check fuel pressure but that's not holding back spark.
I replaced the crank sensor with another OEM unit that I had in stock. It's not new, but it's the same sensor. I also did the test manually turning engine with key on and I see alternating 10V DC and 0V DC at the actual sensor.
I also checked again and I'm getting 170 RPM while cranking through OBD.
I tried swapping another PCM that I had just gotten back from my tuner. Same results, no spark.
I did find some O2 sensor wiring that was goofy. Fixed that. No help.
I also tracked down the grounds that go to the rear of the heads and I had already connected those.

I posted another thread asking a specific question on whether there's a test to see if the PCM is communicating with the coils or not.

I'm at a loss as to what else might prevent the coils from firing or prevent the PCM from telling the coils to fire.....

ksousa

Solved:
I inherited this harness and not really sure what it came out of. I thought they would only go on one way, but I was wrong. I had the driver's side injector and coil harnesses flip flopped with the passenger side harness.
Confirmed by ringing out wires to the PCM and by reading the little numbers denoting cylinder # on the injector plug.......
Once I flipped them (had to extend a few wires to make it reach so I'm thinking originally this harness entered the firewall closer to the passenger side??), hit it with some starter fluid and she fired.

Thanks to all input.

mrvedit

Great to hear that you solved the problem.
Still strange that you got no spark; with the left/right harnesses switched I would still have expected spark, just at the wrong time.