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[Roadburn]

Just installed new cam chain and tensioner. Pulled heads and cylinders cleaned carbon from heads and pistons. Put everything back together, cam timing is correct and have no spark. Have tried new crank position sensor, head temp sensor. Have another bike and borrowed parts from it with no success, like coil, wires and plugs, ECM and SERT. Still no spark. Has anyone run into this problem and what was the fix? Bike is 2007 FLHTCUSE2 with 102,689 miles.

[Twolanerider]

If you've covered all the bases it's time to consider other potential bases.  Are you sure the plug wires are on correctly?  We no longer use dual fire coils.  The wire to the right side should go to the rear cylinder.

Troubleshooting can be a bitch sometimes.   Chasing crushed or damaged wires in a harness or who knows what else is never fun.  Good luck.

[ozrider]

If it was running before the cam change then one would think it may be something simple, like a loose connection,,,

and, or, you didn't mention checking the fuses ?

[Steve Cole]

Do a compression test. If the compression is low then you've installed something wrong, if not you can rule that out and move onto other things you had taken apart.

[Roadburn]

Yes I did check all fuses on both sides of the bike. I also removed outer fareing and double checked all wireing connections in there. And yes it was running when I took the motor apart. I have not done a compression test yet. Will try that next

[grc]

If you really aren't getting a spark, checking compression isn't going to fix that.  Have you actually verified with a test device that you aren't getting the proper output to the plugs?

Jerry

[chicoman]

If you really aren't getting a spark, checking compression isn't going to fix that.  Have you actually verified with a test device that you aren't getting the proper output to the plugs?

Jerry

No compression, no spark, checking compression verifies that.

[Doc 1]

You have to have the plugs in the head so the ecm sees compression, put another set of plugs in the wires and ground them to see spark.
Doc

[grc]

No compression, no spark, checking compression verifies that.

Sorry, but that isn't correct.  If you want to test for proper spark, you need to insert a test device between the plug wire and the plug, with the plug still installed.  Checking compression only tells you how much, if any, compression you have.  It tells you absolutely nothing about the secondary ignition system output.

Jerry

[Steve Cole]

Jerry

The HD Delphi EFI will not issue spark unless there is min. compression, safety feature or so they call it. It take a min. of about 120 psi for the ECM to issue spark and this is why I said to do a compression test. It rules out an assemble issue as the reason for a NO spark condition.

[grc]

Jerry

The HD Delphi EFI will not issue spark unless there is min. compression, safety feature or so they call it. It take a min. of about 120 psi for the ECM to issue spark and this is why I said to do a compression test. It rules out an assemble issue as the reason for a NO spark condition.

Yup, I'm aware of that Steve.  But that doesn't mean the "compression verifies spark" comment is correct.  Compression that meets the minimum requirement might eliminate that one possibility as a reason for having no spark, but it doesn't mean if you have compression you will have spark.  Perhaps I'm just not connecting with what the other folks think they are telling us.  I have that problem on occasion as well, assuming I've made myself clear when in fact what I typed was as clear as mud.

Jerry

 

[Steve Cole]

No, Compression does not mean spark but the lack there of does. Since he had the cam chest apart it kind of helps rule out any errors there.

[grc]

No, Compression does not mean spark but the lack there of does. Since he had the cam chest apart it kind of helps rule out any errors there.

I agree, and usually if something runs fine before you mess with it and doesn't run at all after you mess with it, it's probably a good idea to check whatever you did for errors before setting out in a new direction.

Btw, since I've got the ECM expert here, can you enlighten me on how the ECM detects cylinder pressure or lack thereof?  I remember reading that it somehow shut down the ignition if it detected a major loss of compression, but I've never seen an explanation of just exactly how it manages to do that. There is no direct sensing of cylinder pressure I'm aware of, unless they included that capability in the ACR's.  I've never pursued the subject because frankly I've never had need to do so. 

Jerry

[Steve Cole]

It's a rate of change circuit. If the starter motor turns the crankshaft at a steady speed then there is no compression thus no spark. If the crankshaft speeds up and slows down then we should be able to tell what cylinder is what by measuring when the speed up and slow down occurs. Now we know what's what, the ECM will begin to issue fuel and spark to the correct cylinders for start-up. Saves putting a cam trigger on the bike and the problems that go along with something else to fail.

[grc]

Thanks Steve.  That clears up the mystery for me.

Jerry