Diagnostic Path

Darren Technician Wisconsin Posted   Latest  
Resolved
Driveability
2016 Ford Explorer 3.5L (8) 6-spd (6F35)
Crank / No Start

No codes. Cranks good no start no spark.

So I had a few minutes to check this out before I left for work today.

I have good injector pulse, that I checked with the pico scope and current clamp.

Tailpipe has 30,000 ppm hc cranking showing good fuel, sounds high but no biggie.

I am assuming there is no spark on all coils because there is no signs of life.

For sure I have no spark from the 3 front coils that are easy to access.

I have battery voltage on both terminals of the coil connector while cranking with connector plugged in.

The coils have no primary signal from pcm.

Scanner shows 250 rpm cranking.

I am curious as to what your diagnostic path would be at this point…

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Interesting
Glenn Owner/Technician
Texas
Glenn
 

Hi Darren, I recall there were a lot of issues with these if a coil went bad it would take out the coil drivers in the PCM. There should be a TSB on this. As I recall the PCM and all coils had to be replaced when this happened. The Taurus and the Explorer both had this issue. I have been searching for the TSB, but have not found it in my history files yet.

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Helpful
Anura Educator
New Zealand
Anura
 

Hi Darren, Scope the crank waveform with Pico, see the integrity, if happy, then scope cam too with crank and see the correlation with a known good one.. Cheers, Anura

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Caleb Diagnostician
Indiana
Caleb
 

Cam crank correlation for sure. You can check the integrity of the signals at that point too. Are these 3 wire coils?

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Darren Technician
Wisconsin
Darren
 

2 wire

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Darren Technician
Wisconsin
Darren Update
 

Thinking out loud, can my cam crank correlation be off and still have injector pulse?

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Glenn Owner/Technician
Texas
Glenn
 

Hi Darren, You would have injector functions and coils fire the same, they would just be out of time. The crank sensor is what trigger the coil drivers in the PCM, the cam is what triggers the injectors through the PCM.

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Caleb Diagnostician
Indiana
Caleb
 

My opinion to your question is how can we know the strategy of every PCM?? Much easier to just check cam/crank versus overthinking it. Dunno I'm simple lol.

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Alex Diagnostician
Australia
Alex
 

Darren, so this is a crank no start, with a crank sensor signal (250rpm on scanner; is tacho on dash moving during crank? ), working injectors, power at the 2 wire coils, but no coil control. Hmmm. Are coils controlled via an driver/power transistor external to pcm? If so, is dead? If driven through pcm, is pcm drivers dead?

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Rusty Owner/Technician
Massachusetts
Rusty
 

If KOEO self-test is an available scan tool option, I’d run that and see what results. I don’t think Ford has a bi-directional test for individual coil primary circuits, but if so,I’d be doing that. I‘d be load testing PCM powers and grounds with a headlamp.

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Sean Technician
California
Sean
 

How did it fail? Customer driving and it stalled or it was running fine then just became a no start? did you check mode 6 data to see if a cylinder was misfiring prior? Pretty sure it wouldn’t be immo… so yea next step would be getting a visual on the pcm connectors / checking powers and grounds, make sure I’ve checked for codes on both sides of scan tool, then cap discharge…keep us posted.

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Darren Technician
Wisconsin
Darren
 

Ran fine, just didn’t start.

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Rod Diagnostician
California
Rod
 

30000 hc under those conditions sounds right with proper fuel delivery. I have not looked at the schematic , does that system have the ignition primary drivers in the pcm? ( most likely) Next I would disconnect the accessible coils and “disconnect” the other three at the pcm , put a test light across each connector at a time and look for pulse while looking at current flow with inductive amp…

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Darren Technician
Wisconsin
Darren
 

Sounds like they need you. lol Thanks for advice

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Rod Diagnostician
California
Rod
 

LOL more than I need them

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Glenn Owner/Technician
Texas
Glenn
 

Hi Rod, (ref. to the funny side note.) That sounds like a real ‘slam dunk’, ‘parts cannon’ kind of place to work at. Any tools or reading skills required? Educated people need not apply? You Tube arm chair diagnostic experience welcome?

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Rod Diagnostician
California
Rod
 

You tube certified. Schedule one federally controlled substance addiction a plus . On the serious side ,let me know what you find on the vehicle you are working on.

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Funny
Rod Diagnostician
California
Rod
 

Also ,what was the lambda reading ? just curious , having fuel control or not also helps as part of the evaluation.

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Glenn Owner/Technician
Texas
Glenn
 

Hi Darren, Diagnostic Path Suggestion: - Check for any TSB's that resemble the problem. - Do a quick internet search with some of the owner forums. - Review the Description of Operations in the Service Information. - Download a wiring diagram and print it off then study it. Be sure to not overlook fuses involved. - Start testing from the easiest to the most difficult until you run into an…

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Darren Technician
Wisconsin
Darren Resolution
 

Disconnected battery for half hour, and jumpered battery cables together, and it fired right up!!!! Clearly this isn’t a fix, but if I find out what really happened, you guys will be the first to know. Thank you again!!!!

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Sean Technician
California
Sean
 

Cap discharge to the rescue, cool… thanks for the update. also it’s a perfectly reasonable fix!

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Glenn Owner/Technician
Texas
Glenn
 

Hi Darren, That procedure works on newer tractors also, I just finished a Massey Ferguson 4710 yesterday and had some crazy issues. I disconnected the battery and crossed the cables together and went to lunch. When I came back and reconnected, the tractor was perfectly normal again. I also recall earlier Fords would have “learned memory” issues and the computer would not clear a fault until…

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Rod Diagnostician
California
Rod
 

Are you using a 1 ohm resistor to avoid spiking other modules?

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Alex Diagnostician
Australia
Alex
 

Rod, interesting comment. I do use these myself based on advice, but must admit I haven't understood how it works, given 1ohm is very low and the current flow in V spike would likely be tiny and largely unaffected by 1ohm I would think. Be very interested in any further elaboration/explanation you may have. Thanks for the tip and cheers. Alex

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Rod Diagnostician
California
Rod
 

A voltage spike can be very high with very little current , a one ohm resistor will suppress the potential high voltage spike that can corrupt another module programing. An example I remember from the mid 90's was the ford taurus that would lose the idle strategy on every start because some one had installed a starter solenoid that did not contain spike suppression , spike suppression can be…

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