4905 Repower/6V92 DDEC help needed

wildbob24 · June 09, 2017, 05:16:12 PM

Guys,

I am trying to help Atlanta bus Guru Ray Cox finish a 6V92 repower in a Buffalo. The engine is electronic, DDEC 2, and we have, thus far, been unable to get it to start. I have a Pro Link and the DDEC 2 troubleshooting manual and have meticulously followed the TS steps all the way to the last step which says to replace the ECM.

I'm not totally convinced the ECM is dead and am looking for someone who might have a known good DDEC 2 ECM for a 6V92 LH that we could borrow/rent before we spend the bucks for a new/reman one.

I know it's a long shot, but thought I'd try anyway.

Thanks,

Bob

luvrbus · June 10, 2017, 05:26:21 AM

The DDEC 11 is touchy about the voltage ,I hope you didn't accidentally get a 24v jolt of current if so it fried.Take it to DD dealer and have it checked

wildbob24 · June 11, 2017, 09:11:35 PM

Clifford,

I'm coming into this a little late in the process. I'm pretty sure that they would not have connected it to 24 volts but I'll ask them just to make sure. If they did, that would explain a lot.

Bob

Scott & Heather · June 12, 2017, 05:24:41 AM

Bob, it turns over but just won't fire? I have spent tons of time troubleshooting the same issue with my DDEC II 8v92. I have some ideas. There are just a handful of things that cause a no start. You really need to contact ken Arnold. He helped me a ton with troubleshooting. I'll see if I can help, but do let me know if it's turning over but not firing

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wildbob24 · June 12, 2017, 05:43:38 AM

Scott,

Yes, it's turning over but not firing. No smoke, nothing.

Oh, and it was setting a coolant level code but we addressed that and now no codes and still won't fire.

Ken Arnold is on my list to contact. Jack Campbell also recommended him.

Bob

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Scott & Heather · June 12, 2017, 06:35:44 AM

Bob, yes a low coolant level will cause it to have trouble. But low level sensors like that won't prevent a start, coach should start and run for a several seconds before those sensors shut it down. The big question for me which ken helped me track down is do you have 12 volts power to the ECM? You gave two different places that absolutely need 12 volts for it to start. The 12 Volt power connector to the ECM, and you have to have 12v at pin 439 at the ECM harness. Pierce the wire with a automotive check light and see if you have 12v at pin 439 and check if you have 12 volts at the 12 volt power connector. Leave the harness plugs plugged in for this. If you do have power at the power connector for the ECM but do NOT have 12 volts at pin 439, let me know. Here's the schematic:
http://84.204.204.67/Electro/SK20627.pdf

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brmax · June 12, 2017, 06:55:41 AM

Just for tips; finding great diagnostic connectors of some sort or brand of your choosing can help.
I pass this on in good faith that road salt and calcium chloride from winter roads is Hell on wire punctures ( starts that green stuff ).
In some situations using a dab of silicone afterwards is a great step.

http://www.tooldiscounter.com/ItemDisplay.cfm?lookup=SAG23500&source=froogle&kw=SAG23500&gclid=CMCC3dS3uNQCFYOBaQodOo4FLA#

My diagnostic teachers cringed at me saying paper clips!
Anyhow good luck with finding the culprit circuits

Floyd

jmblake · June 12, 2017, 07:04:56 AM

Bob, I also chased this problem and Jack kept telling me the same about having power to the ECM. What I found was when I would remove the plug I would have power at the harness, so I figured I was good but still no start. What the problem was about 5" up in the harness that wire was broke and when I would unplug it and bend it back to check for power they would connect together enough to show power, then when I would plug in it would separate and no power again. I also found 4 other wires about to break and fixed them, as soon as I fixed them and plugged it back in it fired right up. Good Luck Jason

luvrbus · June 12, 2017, 07:24:18 AM

Have you checked the the TRS behind the cam pulley some times it gets loose or is moved in engine swaps.

Scott & Heather · June 12, 2017, 08:28:54 AM

As cliff said, trs could cause the no start issue...generally it's just a few things that can cause this. Trust me, I spent 4 days studying the DDEC II troubleshooting Manual. Chasing down a possible broken wire is something you need to do after making sure you have 12v to the power connector and to pin 439. If those both check out good, then starting heading down a different path.

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wildbob24 · June 12, 2017, 08:51:56 AM

Thanks for all the replies. I'm afraid I wasted your time.

Further investigation this morning has determined that we, in fact, are working with a DDEC 4 engine. So, that explains why the DDEC 2 computer wouldn't work.

Again, I'm coming into this late in the process, trying to help these guys out. It's a little like the blind leading the blind, I'm afraid.

I'm WW Williams now getting. DDEC 4 computer tested.

Thanks again,

Bob

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luvrbus · June 12, 2017, 09:32:54 AM

That good it's a DDEC 4 they are 12 or 24volts,I have a DDEC 4 application manual I can send you if you like they are a lot better than a trouble shooting manual

wildbob24 · June 12, 2017, 12:29:44 PM

Clifford,

I agree that the discovering that it is DDEC 4 is a good thing. I just wish I knew that from the start. Wasted a bunch of time on this thing.

Yes, that manual would be helpful and appreciated. I'll PM my address.

Thanks,

Bob

Scott & Heather · June 12, 2017, 05:37:40 PM

Haha. Ok nice. That sure makes a difference. And I was all ready to get down and dirty with the schematic.. disappointed

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