Long crank, no faults

[Jimmy Brooks]

The main correlation that I’m fixated on is with the no spark discovery yoy made and the fact that my pistons had a clean spot as if fuel has been spraying on them and not igniting. I’ll let you know what I find when I borescope it

 

[greiswig]

It would be really interesting to make a temporary system with two electrically-separated batteries: one that supplied the starter, and one that supplied the rest of the system including a relay to that second battery. See if keeping the ignition system and computers above a threshold of voltage made any difference on a vehicle with this symptom.

 

[Adrien]

It would be really interesting to make a temporary system with two electrically-separated batteries: one that supplied the starter, and one that supplied the rest of the system including a relay to that second battery. See if keeping the ignition system and computers above a threshold of voltage made any difference on a vehicle with this symptom.

This would definitely be ideal, the more controlled variables the better. From what I can tell the starter motor is one of the few components on these newer LRs that doesn't have 20 sensors on it lol. So in theory you could power the starter completely externally and the ECM would not know any better. I'm going to wait until Jimmy gets results regarding no-spark test, if he indeed doesn't get spark either I'd be willing to dig further into the ignition system. If he does get spark then I will repeat my test to see if I made any mistakes

 

[greiswig]

My guess is it's not as simple as "spark or no spark." Lower voltage at the coil may result in a weak enough spark to not ignite properly or reliably, but one that would still look like a spark in measuring it.

 

[Jimmy Brooks]

Major favor but could someone that doesn’t have the spark issue give me a video of what the spark should look like as a baseline?

 

[Jimmy Brooks]

Ok, just pulled a plug and cranked the engine with the plug grounded to the body and I can confirm I’m getting low spark (hear the plug clicking but can’t see spark) and I can also smell fuel coming from the open cylinder so I know fuel is getting into there. So now my question is where from here? I know it’s not ECU because I’ve had a junk yard ECU put into the car and no difference. So the car runs fine, just doesn’t like starting and doesn’t make a difference when boosted with a jumper pack. Plugs were replaced last year and coils are still original. Would it be an engine wiring harness issue?? Maybe coils?

 

[ftillier]

I would guess coils, perhaps you can swap coils around and see if the results are the same (just in case some coils are in better state than others). I wouldn't think engine wiring harness issues would manifest this way, though that's really just a guess not based on experience.

 

[f1racer328]

Ok, just pulled a plug and cranked the engine with the plug grounded to the body and I can confirm I’m getting low spark (hear the plug clicking but can’t see spark) and I can also smell fuel coming from the open cylinder so I know fuel is getting into there. So now my question is where from here? I know it’s not ECU because I’ve had a junk yard ECU put into the car and no difference. So the car runs fine, just doesn’t like starting and doesn’t make a difference when boosted with a jumper pack. Plugs were replaced last year and coils are still original. Would it be an engine wiring harness issue?? Maybe coils?

You could try swapping coils around and see if they all have the same amount of spark. Probably a pretty barbaric test but might give you some info.

 

[greiswig]

Ok, just pulled a plug and cranked the engine with the plug grounded to the body and I can confirm I’m getting low spark (hear the plug clicking but can’t see spark) and I can also smell fuel coming from the open cylinder so I know fuel is getting into there. So now my question is where from here? I know it’s not ECU because I’ve had a junk yard ECU put into the car and no difference. So the car runs fine, just doesn’t like starting and doesn’t make a difference when boosted with a jumper pack. Plugs were replaced last year and coils are still original. Would it be an engine wiring harness issue?? Maybe coils?

You may have reached the right conclusion of there really is no spark. I suspect the only way a visual inspection of the spark quality might be valid is if you actually can A/B between that long crank condition and the engine running. Or set up a jig (or handheld screwdriver where you can widen the gap) where you can widen the spark gap to test for peak voltage differences between those two conditions, and even that doesn’t really test current. But it’s going to likely be more precise than “I can’t see it.”

 

[Jimmy Brooks]

Is there not a better way to test the coils like using a multimeter or will that not tell me anything? Another idea is that I could buy a coil and see if I can see any spark difference between the old and new one.

I also forgot to mention that I pulled the coil and plug out of my parents supercharged V6 D5 and was thinking about swapping coils from that but noticed they are different. That car I was able to see spark.