Intermittent start, Supercharged

TylerM

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I had a brand new motorcraft alternator being installed under warranty by Ford that was bad out of the box, diode issues.
Is there a good way to test the diodes with a meter?

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Pentalab

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Is there a good way to test the diodes with a meter?

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Yes, they should be high resistance in one direction, and almost zero ohms in the other direction. Just rvs lead to do this test. IF the piv rating of the diode is exceeded, it will blow in half..and go open circuit.
If excess current runs through it, it will fail shorted. ( zero ohms in either direction).

Typ V drop across the diode, when it's conducting is typ aprx .7 vdc.
 

DieHarder

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Car ran and idled for about 30 minutes on initial start. Dropped e-brake to do a datalogging run and car shut off. Has not started since.

Q: This may be far-fetched but in re-reading your initial description did the car shut off immediately when you dropped the e-brake? By chance, did you run any wiring through the center console/tunnel? If so, may be worth checking if the ebrake assembly pinched/grounded/shorted/opened any wiring running through there.

After that I'd start looking closely at all wiring/harnesses you extended/moved. Go over it inch and inch looking for any cuts, scrapes, sharp bends or other insulation damage; especially where it crosses over sharp edges or through the body. Look at the solder joints/connections. Verify each connection/assignment. Ensure no wiring is swapped/incorrect; really easy to do on a build. (During my supercharger upgrade I spent most of the time on wiring. From your description sounds like you did too).

Best advice I can give you is to concentrate on the PCM issue. Trace the wiring to identify exactly which connectors/harnesses carry the sense lines and check them end to end and then check any associated circuitry. It may be beneficial to loosen up the mountings for both the BEC/PCM to see if that changes your symptoms.

Sorry to suggest this but you may find it necessary to remove any tape/plastic loom for any/all wiring you worked on to troubleshoot this one. On my supercharger build I ended up removing all of the loom/tape from quite a few of the extensions I'd made because I needed to verify I'd extended them correctly and the pin-outs. Only saving grace to all of that extra work is the car ran fine save the grounding issue I chased for two more weeks. I feel for you... Troubleshooting wiring/electrical systems is a pain and takes a ton of time. Recommend posting some pics to give us a better idea of what you've done.
 

TylerM

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Car ran and idled for about 30 minutes on initial start. Dropped e-brake to do a datalogging run and car shut off. Has not started since.

Q: This may be far-fetched but in re-reading your initial description did the car shut off immediately when you dropped the e-brake? By chance, did you run any wiring through the center console/tunnel? If so, may be worth checking if the ebrake assembly pinched/grounded/shorted/opened any wiring running through there.

After that I'd start looking closely at all wiring/harnesses you extended/moved. Go over it inch and inch looking for any cuts, scrapes, sharp bends or other insulation damage; especially where it crosses over sharp edges or through the body. Look at the solder joints/connections. Verify each connection/assignment. Ensure no wiring is swapped/incorrect; really easy to do on a build. (During my supercharger upgrade I spent most of the time on wiring. From your description sounds like you did too).

Best advice I can give you is to concentrate on the PCM issue. Trace the wiring to identify exactly which connectors/harnesses carry the sense lines and check them end to end and then check any associated circuitry. It may be beneficial to loosen up the mountings for both the BEC/PCM to see if that changes your symptoms.

Sorry to suggest this but you may find it necessary to remove any tape/plastic loom for any/all wiring you worked on to troubleshoot this one. On my supercharger build I ended up removing all of the loom/tape from quite a few of the extensions I'd made because I needed to verify I'd extended them correctly and the pin-outs. Only saving grace to all of that extra work is the car ran fine save the grounding issue I chased for two more weeks. I feel for you... Troubleshooting wiring/electrical systems is a pain and takes a ton of time. Recommend posting some pics to give us a better idea of what you've done.
My plan was to lay the harness out again. I ordered the workshop oem wiring diagrams for my specific model year for this purpose.


My neighbor suggested the same about the center console.

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TylerM

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Well I was double checking some things today. Pulled the blower off and spun the rotors. Odd smell coming off. Then I stuck my finger down inside the opening for the bypass valve on the discharge manifold and found this.

Edit: smells like oil. Blower is second hand. I checked my oil and my coolant. No mixing.
ca3eeef58ed1c578cd271549af76821b.jpg


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Juice

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Some oily residue is ok. Have you checked any plugs? If it is oil where its not supposed to be, then the plugs will be soaked in OIL. But you would have had james bond smoke while it was idling if it was an oil issue.
 

TylerM

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Some oily residue is ok. Have you checked any plugs? If it is oil, then the plugs will be soaked in OIL. But you would have had james bond smoke while it was idling if it was an oil issue.
Yeah, didn't have that.

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Juice

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Then dont worry about that oil residue. Fix the electrical issue.
 

TylerM

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Yeah, didn't have that.

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I attempted to crank it a few times before taking stuff apart and it caught but then immediately died. Code had not come back yet.

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If the previous owner wasn't running a catch can you might get oily residue like that. I had a decent oil slick inside my supercharger and intake manifold before using one. It was lighter in color though.
 

TylerM

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If the previous owner wasn't running a catch can you might get oily residue like that. I had a decent oil slick inside my supercharger and intake manifold before using one. It was lighter in color though.
They didnt appear to be. I installed a JLT catch can with the KB on my car.

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TylerM

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I did continuity checks on the wires running from the pcm power relay to the pcm connectors. I have continuity on both wires, .1-.3 ohms on pins 35 and 36 back to the B6 slot on BEC connector for the power relay. I used the OEM workshop manual wiring diagrams for my specific model years. Used that same manual to perform tests on the relays themselves. Both work as intended.

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DieHarder

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Good, one issue resolved.

Do you have the Powertrain Control/Emissions Diagnostics Service Manual for your model year? It's 10 pound book of troubleshooting procedures... In you don't I can send you the troubleshooting procedures for the PCM High Sense circuit fault but the scan file is too large (9 pgs) to post so pass me an email address if you want it and I'll send it to you.

If you can get one highly recommend a high end OBD/Systems/Sensor diagnostic tester for reading codes and conducting tests. It'll really help you narrow down sub-system/wiring issues faster. If you can borrow one that would be ideal.

At this point recommend being very methodical in your troubleshooting. If you can do printouts and take notes that will help you keep track of what you've tested/verified good/bad. If the PCM relay troubleshooting tests out good then start looking at everything you've done wiring wise. Check your wiring extensions and their assignments. In addition to end-to-end continuity checks are the pin assignments correct? If you've accidentally switched wiring and grounded the wrong end or something is shorted that would help explain what you're experiencing.

Another point from re-reading your initial post. Says you could not start the car after bolting down the supercharger. May be an outlier but any chance you pinched/grounded/cut any wiring when you did that?
 

TylerM

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Good, one issue resolved.

Do you have the Powertrain Control/Emissions Diagnostics Service Manual for your model year? It's 10 pound book of troubleshooting procedures... In you don't I can send you the troubleshooting procedures for the PCM High Sense circuit fault but the scan file is too large (9 pgs) to post so pass me an email address if you want it and I'll send it to you.

If you can get one highly recommend a high end OBD/Systems/Sensor diagnostic tester for reading codes and conducting tests. It'll really help you narrow down sub-system/wiring issues faster. If you can borrow one that would be ideal.

At this point recommend being very methodical in your troubleshooting. If you can do printouts and take notes that will help you keep track of what you've tested/verified good/bad. If the PCM relay troubleshooting tests out good then start looking at everything you've done wiring wise. Check your wiring extensions and their assignments. In addition to end-to-end continuity checks are the pin assignments correct? If you've accidentally switched wiring and grounded the wrong end or something is shorted that would help explain what you're experiencing.

Another point from re-reading your initial post. Says you could not start the car after bolting down the supercharger. May be an outlier but any chance you pinched/grounded/cut any wiring when you did that?
I can do a more detailed write up after work about what has been done so far. I would greatly appreciate those scans, that manual is next on my list. I have the wiring manual attached below. I'll be in boxing my email.

No wires were pinched bolting it down. I double checked before actually bolting it down to prevent being short sighted again and forgetting something else.
01058a22fb1e2827fe9e4639c85a5da8.jpg


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DieHarder

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I have the Workshop Manuals Vol 1,2 and the Wiring Diagrams. This one's different. Here's the manual I'm talking about; true step-by-step troubleshooting guidance... just email me for the PCM 0906 troubleshooting section.

IMG-1496.jpg IMG-1497.jpg
 

DieHarder

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The PCMRC's are on pg 5-8/9; the pg shows different types of power relays and the pin connections. ID which type your car has to test the pinouts. Attached is the layout for 170 pin PCM connections.
 

Attachments

  • PCM Connector Pinouts.pdf
    1.2 MB · Views: 3

TylerM

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Which ground would be ideal to test the circuit according to the pinout test?

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