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Crank, no spark. Stumped. Need gurus!

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Old 12-04-2018, 08:53 PM
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Crank, no spark. Stumped. Need gurus!

I am stumped. Stopping for the day to regroup. Just need outside help.
Was driving, came to a red light and engine died (no check light came on). Tried to restart and engine would crank but not start. Got the car home via tow. And the initial tests began. Came to find no spark at spark plugs. Time to pull out the repair manual. Started my way down Chart C-4A. Ended up replacing the Ignition Coil, The Module, The Pick-Up Coil, Distributor Cap and Rotor (all were old or used parts I had put in) finally made it all the way down the diagram, still with no spark. So checked the spark plug wires for resistance, they were still good. Checked Fuses, good. Checked Codes, just 12. So I checked the resitance from Aldl Connector 'M' to ECM harness, no breaks. Then went through and checked Volts at ECM harness, all matched up besides: Bypass BC7 (7.3v instead of 0), EST BC8 (6.6v instead of 0), Reference BD8 (10.3v instead of 0), and Reference Low BD9 (10.6v instead of 0). Pulled out wiring diagram, found all wires were from Module to ECM. Thought maybe the resistors in ECM werent closing so I replaced the ECM. Still no Spark, but will crank. Going to recheck volts at ECM in the morning out of curiousity. But now i'm stumped and would like some outside feedback. Any ideas? What am I missing?



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Old 12-04-2018, 11:56 PM
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Re: Crank, no spark. Stumped. Need gurus!

Sounds like ignition control module, double check that or any wiring to do with it , friend had an issue recently with a sensor , ended up being the wiring as it went through the firewall.
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Old 12-05-2018, 01:37 AM
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Re: Crank, no spark. Stumped. Need gurus!

Brand new module and wiring is sound.
also ran a diagnostic test on the brand new module just in case and it cleared. Have 12v power to the ignition coil and have 12v power to the module with key on.

Last edited by lcmchefslife; 12-05-2018 at 01:43 AM.
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Old 12-05-2018, 01:41 AM
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Re: Crank, no spark. Stumped. Need gurus!

Can you test the module? Maybe it's a faulty new part
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Old 12-05-2018, 01:44 AM
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Re: Crank, no spark. Stumped. Need gurus!

Originally Posted by zs&tas View Post
Can you test the module? Maybe it's a faulty new part
was just editing my earlier post. I did test it.
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Old 12-05-2018, 02:50 AM
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Re: Crank, no spark. Stumped. Need gurus!

Oh lol. Check ground wires for everything so coil, block, computer . Just throwing out what I'd do next ?
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Old 12-05-2018, 06:57 AM
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Re: Crank, no spark. Stumped. Need gurus!

Did you check for 12 volts at the positive coil terminal? With key on, voltmeter on positive terminal and ground going to chassis or engine block.
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Old 12-05-2018, 10:06 AM
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Re: Crank, no spark. Stumped. Need gurus!

Originally Posted by 3.4 grape View Post
Did you check for 12 volts at the positive coil terminal? With key on, voltmeter on positive terminal and ground going to chassis or engine block.
Yes there is 12v.
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Old 12-05-2018, 10:07 AM
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Re: Crank, no spark. Stumped. Need gurus!

I'll check the grounds again today.
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Old 12-05-2018, 03:45 PM
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Re: Crank, no spark. Stumped. Need gurus!

If every electrical device in the Ignition system checks out and is in fact operational , and if both positive power and negative ground are in fact proper , there is one other thing that comes to mind here ;

Are you sure your distributor is actually turning when your cranking the starter ?

There was a thread here some time ago where a poor guy had the very same thing , good +12 volts , good grounds , replaced all Ignition system components not once but twice , and no spark . Come to find out he had no spark because his timing chain had broken and of course his camshaft and distributor weren't turning . Easy enough thing to check , take the distributor cap off and have a helper crank the starter while you look at the rotor , hopefully it does turn as the starter is cranked .....
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Old 12-05-2018, 04:17 PM
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Re: Crank, no spark. Stumped. Need gurus!

Are you sure its a no spark situation? That is have you pulled a spark plug wire connected a spark viewer or a grounded spark plug and cranked over the car to make sure there is no spark? Could it be a fuel delivery issue. Based on your detailed diagnostics above I'm assuming you checked this already.

The parts you replaced are they all bolted in correctly, don't laugh Ive seen people plug in a ignition module or other electronics hanging loose and it not work because it grounds through the mount screws. Also the module usually has heat transfer grease make sure you used that if its heating up it can cause an issue (and fry itself).

Did you also verify the coil to distributor wire was good, and the coil wire and spark wires were correct for the new distributor cap, there are different styles and sometimes they don't make good contact.
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Old 12-06-2018, 03:29 PM
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Re: Crank, no spark. Stumped. Need gurus!

So yes, grounds are good. Did the old screwdriver trick on the spark plug wires, the coil wire, and the distributor side (for good measure). And no spark anywhere. The only think i havent checked is if the rotor is actually spinning (will check that) the thing that keeps catching my eye is that at the harness at the ecm the 4 wires (mentioned in 1st post) are the 4 pin connector to the module. What could be causing those to stay open at 10v instead of 0v, on key on. Was gonna unplug the harness and check to see if the ecm is causing it or the module is. I know its a rare oddity, but could my Mem-Cal be ****ed?
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Old 12-06-2018, 03:40 PM
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Re: Crank, no spark. Stumped. Need gurus!

Humm yeah I would test the wires at the ecu with the module disconnected.

You said you replaced your ecu, did you take your rom Chip out of the old ecu and put it in the new ecu.

There is a little wireing block beside the battery that has several wires with fuse able links I had bad contact there and it caused all sorts of odd faults, when I took it off and cleaned the terminals I missed one and that took a while to figure out.

I solved most of my electrical issues by doing an LS swap lol

Hopefully it's not timing chain or distributor gear/cam gear...
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Old 12-06-2018, 03:43 PM
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Re: Crank, no spark. Stumped. Need gurus!

Pretty sure its not timing, cause it cranks, theres still good compression. I also checked the fuel pump and relay (justfor giggles) and they were fine. I'll check the fusible links, but im sure they are fine. Doesnt hurt to check though.
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Old 12-06-2018, 03:50 PM
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Re: Crank, no spark. Stumped. Need gurus!

Ok yeah just snowballing ideas at this point if your rotor is turning and you did indeed move the chip over to the new ecu ( they ship without a chip) I would buy a new ignition module even though you tested it as good, sometimes the resistance tests don't show faults. Does your car have vats?
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Old 12-06-2018, 04:52 PM
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Re: Crank, no spark. Stumped. Need gurus!

Yea moved the whole Mem-Cal over from old ecm. And after replacing the module, i took it off again and warrantied it and got another one. And Vats does pass, otherwise the security light wouldnt go off and the starter wouldnt crank the engine.
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Old 12-06-2018, 05:22 PM
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Re: Crank, no spark. Stumped. Need gurus!

Ok so the connections at ecm are as followed...
-connector plugged in, key-on:
Bypass BC7: 7.2v
EST BC8: 6.4v
Reference BD8: 10.3v
Reference Low BD9: 10.5v

-connector plugged in, key-run:
Bypass BC7: 6.2v
EST BC8: 4.4v
Reference BD8: 7.4v
Reference Low BD9: 7.4v

-Connector unplugged, key-on:
Bypass BC7: 12v
EST BC8: 0v
Reference BD8: 11v
Reference Low BD9: 12v

-Connector unplugged, key-run:
Bypass BC7: 9v
EST BC8: 0v
Reference BD8: 8v
Reference Low BD9:9v
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Old 12-06-2018, 05:25 PM
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Re: Crank, no spark. Stumped. Need gurus!

Vats module tend to fail in parts sometimes it will ground the starter relay but not send the enable signal to the ecu. But that disables injectors and pump, I don't think it disables spark...

Man if your rotor is turning, could it be a second bad ecu, maybe someone local could try your ecu in this car? Let us know if you figure it out I'm stumped.
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Old 12-06-2018, 05:28 PM
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Re: Crank, no spark. Stumped. Need gurus!

Just checked dizzy and it turns.
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Old 12-06-2018, 05:31 PM
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Re: Crank, no spark. Stumped. Need gurus!

What voltage do you see at the fuel pump enable relay on the engage wire (not the battery wire)? for the fun of it try adding a temporary ground wire to the coil just to make sure its fully grounded, and also take a jumper cable and connect between block and body to make sure you have a good ground to both the engine and body (maybe the ground strap broke or came off?)
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Old 12-06-2018, 05:37 PM
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Re: Crank, no spark. Stumped. Need gurus!

one other thought does your tach show any RPM's when you are cranking over the car...
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Old 12-06-2018, 05:45 PM
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Re: Crank, no spark. Stumped. Need gurus!

No the tach doesnt thats why i originally replaced the pickup coil.
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Old 12-06-2018, 05:53 PM
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Re: Crank, no spark. Stumped. Need gurus!

Hmmm....I believe I'd be making sure the pickup coil isn't the issue...

How long ago did you replace it, and was it a new, used, OEM, or aftermarket pickup coil?

EDIT: reread your original post, and see that the pickup coil was replaced after your issue started...correct?
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Old 12-06-2018, 06:00 PM
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Re: Crank, no spark. Stumped. Need gurus!

Yes brand new oem replacement. And i just rechecked the resistance and its fine. Also double checked to make sure my dizzy pole had magnetism and it does.
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Old 12-06-2018, 11:31 PM
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Re: Crank, no spark. Stumped. Need gurus!

Might be the ignition switch was failing when you first stalled. Sometimes the switch is intermittent before completely failing. Contact on the switch do wear out.
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Old 12-06-2018, 11:52 PM
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Re: Crank, no spark. Stumped. Need gurus!

You know I did have that thouhht, but then the starter enabke relay wouldn't be working....correct?
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Old 12-07-2018, 12:06 AM
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Re: Crank, no spark. Stumped. Need gurus!

If the ignition switch is bad it's possible the starter circuit is good, but the ignition power is supplied in the run position but not while cranking the engine. Should be supplied in both positions.

Have you verified voltage at the ignition module and ecu while cranking the car over?

Are you sure the vats starter relay hasn't been bypassed in the car? Again it's possible the starter circuit in the vats module to work but the part that sends the 35hz signal to the ecu to fail.

Check your starter and make sure all the wires that pick up power there are good.

Maybe claim the ecu as bad for warranty exchange, don't forget to keep your chip.
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Old 12-07-2018, 12:15 AM
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Re: Crank, no spark. Stumped. Need gurus!

I had my ignition switch fail on my 88 firebird without the anti theft you are dealing with. The car stalled on several occasions but usually restarted. Then it stalled and would crank but would not start. It was less than $ 30.00 so if not else works it might be worth a try. Bad ignition contacts can result in low voltage when cracking.
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Old 12-07-2018, 12:22 AM
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Re: Crank, no spark. Stumped. Need gurus!

Good point...He could test the switch. The switch is under the dash about mid way down the column not where the key is, you could simply make jumper wires, unplug the switch, put your key in and move it to the run position so vats picks up the key and then use the jumper wires down at the switch to mimic what the switch does.
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Old 12-07-2018, 12:41 AM
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Re: Crank, no spark. Stumped. Need gurus!

Are your injectors pulsing while cranking (not sure if the 6cyl cranks on individual injectors or the 7th cold crank injector... It's been a long time since I touched a v6 thirdgen. I'm assuming no cam/crank sensors and it's just timmed off the pickup for both spark and pulsing the injectors.

Last edited by Aviator857; 12-07-2018 at 12:45 AM.
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Old 12-07-2018, 12:47 AM
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Re: Crank, no spark. Stumped. Need gurus!

Cold start injector on V6 located rear of engine next to distributor. It is controlled via cold start switch in front of the engine next to CTS. If the cold start was not working the engine would probably start with start spray.
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Old 12-07-2018, 12:55 AM
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Re: Crank, no spark. Stumped. Need gurus!

Is there a relearn procedure that he needs to do after replacing all the parts? Maybe disconnect battery over night and see?
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Old 12-08-2018, 08:08 PM
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Re: Crank, no spark. Stumped. Need gurus!

Did you check to see if the 12 volts at coil is not there when cranking? Below is a link to a no start diagnose video on a GMC

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