Inject Resp Time Long

richard5933 · February 11, 2019, 12:45:38 PM

Can't speak specifically how yours works, but on my bus when the engine shut itself down I was able to restart by holding the over ride switch. It allows the engine to run despite a safety circuit telling the engine to shut down.

Of course, before using the over ride I do my best to confirm that there is oil pressure (mechanical gauge in engine bay), that there is coolant in the system, and that there is not an obvious overheat situation (infrared thermometer).

Hopefully others with more experience with your setup will be able to confirm, but what I'm thinking is that when the bus shuts itself down and you can't restart you might test by holding the over ride and see if it will start. That would tell you that the problem is in the safety shut down systems. Then the hunt begins.

DKO · February 11, 2019, 12:51:52 PM

Ok, I understand that. That is how my override switch would operate if I understand correctly. I was thinking you might be suggesting a way to test something now, before another shutdown situation. Thank you for the suggestion and information. I appreciate your interest.

Davy

Boomer · February 11, 2019, 04:53:53 PM

You can diagnose your own DDEC issues by procuring the Detroit CD tool and simply using your computer. Just need the CD, interface box and cable. This will diagnose faults, enable configuration changes, show driver reports, and much more. Much more extensive than the DDC Pro Driver on your dash.
Get the final DDEC IV version which will cover your DDEC III. You might even find one on ebay. Or, you could install a Silverleaf VMS.

Iceni John · February 11, 2019, 07:19:42 PM

Are you sure your DDEC is getting sufficient voltage under load? By that, I mean if other electrical loads are also on at the same time. I don't know exactly what the minimum voltage is for DDEC, but I had something similar happen to me a few times. The engine would suddenly die without any warning, then after coasting to the side of the road I could restart it every time without a problem. The last time it happened was in the yard where I store my bus - the engine was at Fast Idle to build air, and when I turned on my headlights to check them before driving out the engine died. This time I couldn't restart it - it turned over just fine, but wouldn't fire at all. Hah! Now I knew what's happening. I checked the main 100A fuse on the rear start panel, and its feed cable was so corroded that I'm surprised it passed any current at all. After completely rebuilding the fuse holder and replacing both its cables I've never had the problem again. Strangely, every time the engine died it didn't throw any code that my ProLink could detect.

I've also replaced my useless original quarter-sweep Teleflex voltage gauge with a full-sweep AEM voltage gauge that has enough resolution to easily discern 10ths of a volt. If I ever have voltage problems again I'll be able to easily see exactly what's happening.

John

Boomer · February 11, 2019, 08:27:16 PM

If I remember correctly the critical voltage on a DDEC II is 12.2 VDC.

DKO · February 14, 2019, 08:42:57 PM

I am finding nothing loose, burnt or corroded in the box above the engine. It was hanging down quite a bit more. It was loose before the engine came out, but now so loose that I could not swing the door open without lifting it up. I put some screws in it to pull it back up tight.

These are the connections on the rear start switches.

Does anyone know what these five relays are for? They are not listed on the Prevost sticker on the door at all. Four of them have labels that say Stop, Left, Right and Converter Bypass???.

I have not started the bus since I first posted this, but we have about 80 miles to drive Saturday. I am hoping for no more glitches, but keeping my eyes open.

Davy

bevans6 · February 15, 2019, 04:57:23 AM

Those relays might be to provide a 12V trailer hitch plug.

Dave5Cs · February 15, 2019, 10:32:08 AM

Agree with Brian, mine are just like that same 4 and converter from 24 vDC to 12VDC for my jeep lights when in tow

DKO · February 15, 2019, 12:36:12 PM

Thank you both for the information.

Davy

DKO · February 16, 2019, 05:41:24 PM

I cranked and ran the bus 80 miles today and it did fine. The drive was one hour and forty five minutes and the total run time was about two hours and thirty minutes. My moves the next two weekends will be relatively short. I am hoping this is behind me, but I am open to any ideas.

Davy