DDEC comes on unreliably

[Sebulba]

Hello all,

When we sit for a while, I disconnect the main power switch and turn on our battery tender.

I then turn off the battery tender and turn on the main battery switch.  When I go to start the beast.

I'm not sure this procedure is related to my problem or not, but,  the DDEC doesn't come on reliably. 

Today I started the bus several times working on another thing and so far the DDEC has not come on.

Should I disconnect when hooking up the battery tender?  Am I causing this to happen?  What triggers the DDEC turning on?

Any other ideas?

Thanks

Seb

[Bill Gerrie]

The DDEC power wires are supposed to be connected directly to the battery. Follow the wiring diagram and you should find they are not connected after the battery switch. If they are maybe you should change the power leads to be directly off the 12 volt section of the battery bank.

[Sebulba]

The DDEC power wires are supposed to be connected directly to the battery. Follow the wiring diagram and you should find they are not connected after the battery switch. If they are maybe you should change the power leads to be directly off the 12 volt section of the battery bank.

Hmmm, I don't know if they are connected before or afterthe battery switch.  I just assumed after in that I assumed the battery switch disconnected everything.

Ok, well then I guess that my disconnecting the battery would not be an issue.

The mystery continues.

Seb

[Sebulba]

The DDEC power wires are supposed to be connected directly to the battery. Follow the wiring diagram and you should find they are not connected after the battery switch. If they are maybe you should change the power leads to be directly off the 12 volt section of the battery bank.

Hmmm, I don't know if they are connected before or afterthe battery switch.  I just assumed after in that I assumed the battery switch disconnected everything.

Ok, well then I guess that my disconnecting the battery would not be an issue.

The mystery continues.

Seb

[Sebulba]

Well, now I started up again, and this time the DDEC lit up.

I wish I knew why it comes on sometimes and not other times.

It does seem that when we are traveling every day and don't disconnect main power it just works every day. It seems that when we sit for a week or a month is when this happens.

Seb

[luvrbus]

What in the world are you talking about the small panel on the dash on the DL,   ? the DDEC lit up or you would still be trying to start the engine , the DDEC is on all the time the disconnect switch will not shut the power off to it.All the fuses are in the battery box on the DL except for the shift pad it is under the driver's window in the fuse box,you lost me on this one   

[Sebulba]

What in the world are you talking about the small panel on the dash on the DL,   ? the DDEC lit up or you would still be trying to start the engine , the DDEC is on all the time the disconnect switch will not shut the power off to it.All the fuses are in the battery box on the DL except for the shift pad it is under the driver's window in the fuse box,you lost me on this one

Yes, that small panel in the middle.  And when it doesn't light up, I have no high idle, or turn signals.  There are probably other things that aren't functioning when it doesn't come on, IE. light up.

The engine does start with it not lit up. The second day I owned it, I drive it without it lit up, that's how I know I don't have turn signals when not lit.

Puzzling, huh

Thanks for chiming in.  I truly appreciate your input.  I just would like to feel confident that this will function when ready to roll and wonder what is going on and would like to address it if there is a problem.

Seb

[Bill Gerrie]

When you start the engine do you wait till the CEL and SEL go out before starting? You are to wait till the computer runs a self diagnosis. After the lights go out you start the engine. Sounds like you have a few bad connections.

[Sebulba]

When you start the engine do you wait till the CEL and SEL go out before starting? You are to wait till the computer runs a self diagnosis. After the lights go out you start the engine. Sounds like you have a few bad connections.

Hello Bill,

You may be onto something here. I just hit the master switch and then the start switch.

What do CEL and SEL stand for.  Geussing they may be lights on the dash to wait for?

Thanks

Seb

[luvrbus]

Yes, that small panel in the middle.  And when it doesn't light up, I have no high idle, or turn signals.  There are probably other things that aren't functioning when it doesn't come on, IE. light up.

The engine does start with it not lit up. The second day I owned it, I drive it without it lit up, that's how I know I don't have turn signals when not lit.

Puzzling, huh

Thanks for chiming in.  I truly appreciate your input.  I just would like to feel confident that this will function when ready to roll and wonder what is going on and would like to address it if there is a problem.

Seb

The information panel has a plug end harness it just needs cleaning no fast idle the cruise will not work either ,the turn signals should work they just don't show, the joys of electronics will keep you busy 

[Bill Gerrie]

The SEL (red one) stands for stop engine light which will shut the engine down. It is a major fault. The CEL (yellow one) is for minor faults. It warns you of an issue but won't shut you down. You should have a momentary switch located near the lights which will put the lights into a test mode and if all good will flash 25 on each one.

[Iceni John]

Some years ago my engine would occasionally die without warning while driving, but it would always restart just fine.   One day I had the engine idling, then turned on the headlights to check them:  the engine died as soon as I switched on the lights.   Evidently I had an electrical fault with the DDEC's power supply, but where?   I eventually found that the main 100A feed from the rear start panel to the front junction box had badly corroded 4AWG cables in and out of its Class H fuse.  I replaced the cables and cleaned the fuse's contacts, and I've never had the problem ever again.   The corrosion was causing enough voltage drop at the front JB to make the DDEC power relay there disengage, cutting power to the ECM.   Moral of the story:  cable resistance will cause erratic DDEC performance.

DDEC fast idle is a product of two resistors in the PTO circuit from the DDEC Vehicle Interface Harness to the accelerator pedal that mimics the pedal being partially depressed:  fast idle is not created in the ECM itself, but is part of the pedal's circuit.   With Bill Gerrie's help I rebuilt my fast idle because there was corrosion at the resistors causing it to sometimes not work, or to work insufficiently.   (I now have the world's only two-speed fast idle!   Why not?)   Again, corrosion was causing weird inconsistent glitches.

I suggest you go through and clean every wire and connector, including all grounds to chassis.

John

[robertglines1]

If I read your thread correctly. you have a 60 serries ddec late 1997ish. Prob ddec III. pre egr(that's great!)  The working of ddec is not as complicated as it sounds. Your engine will not start without it!! It controls injectors Fuel supply. Also timming of them. Couple of must. Will not do this without power seperate from main elect system. requires direct battery connection for power+ and neg-.Main reason for this is memory. A seperate power supply from ign switch Wire code 439 + is required to wake unit (that is bus system source for power) =main disconnect on. Been there on this one as I have built total electrical system from burned out system on my 98 prevost. The other front end info system is exactly that. Clean connector of check grounds on coach side. Clifford has been there on this and some of novices have also. You might have DDEC IV there was a change in late 90's My 2000 -60 serries is IV.   Bob

[luvrbus]

You always need to remember the Detroit responsibility stops at the ECM anything past the ECM is the OEM responsibility and that varies a lot from 1 manufacture to another, 99% of the troubles are on the OEM side

[Sebulba]

Some years ago my engine would occasionally die without warning while driving, but it would always restart just fine.   One day I had the engine idling, then turned on the headlights to check them:  the engine died as soon as I switched on the lights.   Evidently I had an electrical fault with the DDEC's power supply, but where?   I eventually found that the main 100A feed from the rear start panel to the front junction box had badly corroded 4AWG cables in and out of its Class H fuse.  I replaced the cables and cleaned the fuse's contacts, and I've never had the problem ever again.   The corrosion was causing enough voltage drop at the front JB to make the DDEC power relay there disengage, cutting power to the ECM.   Moral of the story:  cable resistance will cause erratic DDEC performance.

DDEC fast idle is a product of two resistors in the PTO circuit from the DDEC Vehicle Interface Harness to the accelerator pedal that mimics the pedal being partially depressed:  fast idle is not created in the ECM itself, but is part of the pedal's circuit.   With Bill Gerrie's help I rebuilt my fast idle because there was corrosion at the resistors causing it to sometimes not work, or to work insufficiently.   (I now have the world's only two-speed fast idle!   Why not?)   Again, corrosion was causing weird inconsistent glitches.

I suggest you go through and clean every wire and connector, including all grounds to chassis.

John

Wow!  Like Luvrbus mentioned "always fun dealing with electronics"

Similar experience with a Ford van I had.  I would run out of electricity.  I replace starters.  I bought new batteries.  Everything would be fine then randomly would run out of electricity.  Finally had a auto electric guy look at it.  He carefully felt along the wires from the alternator and found a wire that was corroded under the insulation to the pont that sometimes it would disconnect. Replaced that wire and never had a problem.

Thanks for the input.

Se