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No spark on engine crank. - 99 VW cabio Mk3 NOT Mk3.5

Tiny
CAJUNSPIKE
  • MEMBER
  • 1999 VOLKSWAGEN CABRIOLET
  • 90,255 MILES
New: coil, cap, rotor, coil wire, plug wires, plugs, crank position sensor, battery, electrical end of key switch.
Swapped in substitute ecu, same part number, different suffix. My ecu ends with Q. Swap ends with D. Otherwise same part number.
Verified continuity of crank position sensor center wire back to ecu harness. Verified continuity of distributor sensor center wire back to ecu. Did not check +- on either connector.
Nothing I've changed has made coil spark. Alarm did go off when fresh battery installed. Reset using key in driver door unlock.
Starter cranks normally. Just nothing works to allow the system to spark. This is making me nuts. Any help appreciated.
testing spark by grounding coil output wire to block.
check engine light on with key on.
no codes showing with obd reader.
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Sunday, March 18th, 2012 AT 12:44 AM

18 Replies

Tiny
CAJUNSPIKE
  • MEMBER
  • 13 POSTS
Pic added.
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Sunday, March 18th, 2012 AT 12:46 AM
Tiny
CAJUNSPIKE
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Also removed/cleaned/reconnected valve cover ground and block ground wires.
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Sunday, March 18th, 2012 AT 12:53 AM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Have you checked the camshaft sensor on the distributor
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Sunday, March 18th, 2012 AT 1:16 AM
Tiny
CAJUNSPIKE
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  • 13 POSTS
I tested continuity from the camshaft sensor center wire up to the ecu, thru the harness. If there is a specific way to test the sensor, please let me know.
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Sunday, March 18th, 2012 AT 1:26 AM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check the CMH wiring for short and open circuit back to the computer if okay-have the computer tested-also go this link: http://www.youtube.com/watch?v=itMXO56z1tw
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Sunday, March 18th, 2012 AT 2:07 AM
Tiny
CAJUNSPIKE
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Very good link. I found a similar car in the junkyard. I'll go pull the distributor if it exists, and use it to trouble shoot this issue. 100% thanks for your interest and help. This isn't finished until the car starts.
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Sunday, March 18th, 2012 AT 2:42 AM
Tiny
EXOVCDS
  • MECHANIC
  • 1,883 POSTS
Cam/distributor signal is hot needed on this engine for it to run. The crank signal is the main
input. Crank sensor output should be close to 2V AC or more while cranking.

Thomas
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Sunday, March 18th, 2012 AT 2:48 AM
Tiny
CAJUNSPIKE
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Then that brings up the question of how to test the crank sensor. I just spent 5 hours installing a brand new one.
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Sunday, March 18th, 2012 AT 3:02 AM
Tiny
CAJUNSPIKE
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  • 13 POSTS
I've got a dvom. But thats about it as far as test equipment goes.
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Sunday, March 18th, 2012 AT 3:06 AM
Tiny
CAJUNSPIKE
  • MEMBER
  • 13 POSTS
Again, I confirmed continuity from the center crank position wire to the ecu wiring harness. Not sure what voltage or ground is on wires 1/3. I could test that too if somebody knows which is which.
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Sunday, March 18th, 2012 AT 3:10 AM
Tiny
EXOVCDS
  • MECHANIC
  • 1,883 POSTS
Set to 20V AC and attach the negative lead to battery neg.

Attach positive to crank signal wire.

3 wire sensor, one wire is a shielded/shunt, the other two go to ECM.

I don't have a wiring diagram handy, so you can just check each wire while cranking and post
back the results.

Thomas
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Sunday, March 18th, 2012 AT 3:12 AM
Tiny
CAJUNSPIKE
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  • 13 POSTS
Will do in the morning. Can't say thank you enough, to everybody reading and answering. I will test make sure two wires go to ecu harness before test. Already checked the center wire.
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Sunday, March 18th, 2012 AT 3:20 AM
Tiny
CAJUNSPIKE
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Just fyi, I've posted this problem all over. Ya'll are the first people who seem to actually know what you're talking about. Much appreciated.
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Sunday, March 18th, 2012 AT 3:23 AM
Tiny
EXOVCDS
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Found a sensor wiring diagram. See below (pin 1 & 2 of sensor
harness plug).

Also check the coil for "triggering" by ECM.

- disconnect coil harness plug
- ignition ON
- attach a test light across the two outer pins (1 & 3)
- test light should light-up (confirms coil gets power)
- attach test light across pin 2 & 3
- crank engine. Light should flicker (confirms EMC control of coil)

You can use your DVOM, but depending on speed of screen refresh
reate, you will have to crank several seconds to be sure that readings
change or not.

If you don't get coil control/flicker, speed sensor / wiring or ECM
issue.

If you don't have power at coil. Wiring/power issue.

Thomas
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Sunday, March 18th, 2012 AT 3:29 AM
Tiny
CAJUNSPIKE
  • MEMBER
  • 13 POSTS
Ok on the follow up. Shouldn't make any difference but car was originally from california. Results to be posted tomorrow.

Already confirmed coil wires 1/3 have power with key on. Have not tested triggering yet.
You guys rock.
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Sunday, March 18th, 2012 AT 3:36 AM
Tiny
CAJUNSPIKE
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Major update. Just back from a trip to pull a 3rd ecu from a junkyard 96 cabrio. Without touching anything else, installed the ecu, grounded a plug, cranked it over.
.
.
.
.
.
I got spark. Cranked it a bit more and got a big backfire. I will assume the timing is off and check it from there.
I guess the second ecu I got was either bad or not close enough to work. Whats strange, the original ecu ended with Q. The second one ended with D. The working one has the same part number but ends with B.
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Sunday, March 18th, 2012 AT 11:28 PM
Tiny
EXOVCDS
  • MECHANIC
  • 1,883 POSTS
Good stuff!

I remembered I had a video that I made about not needing a distributor
signal... video was made last December for someone on a different forum.

http://www.youtube.com/watch?v=qRi9PNv51T0

In case someone else is reading this topic at a later date, they can
ignore the hall sensor when chasing a no-start (aside from making
sure that the rotor is aligned correctly).

ECM is always the last item on the "troubleshooting tree".

You're probably down to wrong firing order of wires on the distributor
cap.

Thomas
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Monday, March 19th, 2012 AT 12:13 AM
Tiny
CAJUNSPIKE
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Left ya'll the $30 I promised. For anybody else reading this, I posted this problem all over the net to anybody who would listen. Only these guys were precise enough with their instructions to help figure this out and give me ways to test for the specific issue.

Thanks to everybody.
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Monday, March 19th, 2012 AT 12:18 AM

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