DDEC II, the saga continues....

[wayneswirld2]

Well, the saga continues unfortunately for me.  Short back story...bought a 1988 Gillig Phantom with 6V92T DDEC II.  Engine was running while I paid my cash, shut off after cash transfer like I'd turned the ignition to OFF.  Found THREE blown fuses.... ECM (5 amp), INJECTOR BANK 1 (20 amp), INJECTOR BANK 2 (20 amp).  As far as I can tell, all three fuses had been in their respective holders for ages, but all blown at the same time...very interesting, and very odd.  Replaced fuses with correct amperage new fuses, all three are still good and have not blown.

The engine WILL start with the help of a shot of ether, but dies immediately after I stop applying ether.  I DO have power to the ECM, verified by batery voltage at pin B3 of the ECM's 30 pin connector.  I also have battery power to pins A, B, E, and F of the ECM's injector connector.  I also have a good ground at pins C and D of that same connector.  I do NOT have injector pulse at either of the conncetors outboard of either side of the injector connector for the ECM.

My first concern is exactly WHY those three fuses blew...second concern is what was effected by that.  It's been mentioned to me that I may have a bad/shorted timing reference sensor, but I haven't verified that as of yet.  I would think that I'd have a code for it if it were bad.  Another suggestion is a plugged catalytic converter, again I have verified that as of yet.

Another suggestion is that I may be a faulty ECM, I'm leaning towards that being the culprit.  Anyone have one laying around collecting dust that I could use as a "test" ECM?

Wayne
AUstin, TX

[PCC]

Having gone through that this year, may I tell you that I made a great friend in a fellow in Ohio, works for WWWilliams. I sent him my ECM, and he tested it before selling me a new one.

I live just outside Houston, and nobody else offered to do that for me. I got it figured down to the ECM, and that proved to be the culprit.

Wishing you the best - what a bummer deal.

All the best

Keith
PCC

[wayneswirld2]

Thanks for the info Keith...I think I'm hoping against all hope that the ECM isn't bad....but.........

Wayne
Austin, TX

[Sean]

Have you tried hooking up a DDR or Pro-Link to the ECM and seeing if you can read anything out at all?  That would be my first check, before removing the ECM or anything else.

I was able to buy a DDR on eBay for $70.  However, if you don't have experience with this, it's probably worth the c-note or two to have your local Detroit shop come out on a service call to do this.

My guess is your ECM is fried.  A quick check with the reader will tell you for sure.

Any diesel will run if you put ether in the intake and crank the starter -- that tells you nothing at all.  The ECM controls fuel to the cylinders, and a fried ECM would send no fuel at all.  Thus as soon as the ether stops, the engine does too.

That said, it could be something else, too.  There are several sensors on a DDEC-II engine, and if any of them is out of limits the ECM will shut the fuel off.  It is possible that whatever blew the fuses also fried a sensor.  Here again, a quick read with a diagnostic reader will tell you for sure.

-Sean
http://OurOdyssey.BlogSpot.com

[wayneswirld2]

Oddly enough the diagnostic connector is an OBD 1 style that looks identical to that of a 1995 and earlier  GM product.  I'm seriously considering borrowing a buddies Snap-On scanner that will read OBD1 and see if I can get anything out of it.  If I hold the "engine test" switch I get several codes from the flashing CEL, but from what I've been told the ECM will hold old codes in memory until it's cleared with a scanner...

Wayne

[luvrbus]

DDEC is like any engine check your fuel pump and be sure it is pumping fuel 


good luck

[Sean]

Wayne,

I can assure you that DDEC-II does not use OBD-1, even though the connectors look similar.  It is a proprietary DDC protocol.  DDEC-3 and above use SAE standards.

However, the fact that you can read codes with the CEL is good news -- it means the ECM is not completely fried.  I did not realize you had a diagnostic switch or I would have asked about this.

Post the codes here and one of us can look them up for you.  That will give us a starting point.

-Sean
http://OurOdyssey.BlogSpot.com

[PCC]

Sean is right, AND if you are getting codes, then there is a distinct possibility that the ECM is still alive, and  that is a great development.

[hargreaves]

Sometimes if  the connection at the ECM fuses is corroded it will cause high resistance at the injector drivers in the ECM.This in the end will render the ECM usless. the best way to test this is to make up a wiring harness that will go into the middle connector on the ECM. that is the connector with the two red and two black wires. Run the red wires to a completely separate power source. (external 12 volt battery) Do the same with the black neqative wires. If the engine does not run  the ECM is faulty and needs changing.

Good luck    Gerry

[dickegler]

Hi Wayne,

I maybe able to help.  Sent you a PM

Dick Egler

[robertglines1]

out there but happen to me;89 prevost with 8 v92 DDec II..on left standing behind engine.on top of fuel filter two wire going down to a switch (sensor) had come lose.tightened screw and prob solved..2nd time it happened wire had corroded in same connection..sooooo you can also bypass sensor for test purposes only ( i didn't say that) could have went to ground and blown fuses??from past experience....hope its simple for you and do make sure you have fuel pressure...is part of ddec system....

[Ace]

Blown fuses? Where have I heard this before? My DDEC blew the fuses caused from the previous owner that turned the voltage regulator all the way up in his attempts to keep the batteries charged! When I corrected the real problem and not knowing at that time about the voltage regulator setting, as soon as I turned the key and added juice, ALL my fuses blew!
So it could be a simple over voltage problem you have that is blowing the fuses! Also check the fuses with a DVM. Don't just look at them and think they are good. Mine looked good but the DVM said different!
DDEC 2's don't like loose, dirty, or corroded connections. They WILL cause fault codes even when your sensors are good! 3 main shut down sensors are oil level, coolant level, and coolant temp.. Those are the ONLY sensors that will actually shut the engine down! At least on my 8v92 ddec2.

[stevet903]

First step - When you turn on the ignition does the Check Engine light and the Stop Engine Light come on and then go off after about 5 sec?   

From the Detroit Book:

The CEL is illuminated and a code is stored if an electronic system fault occurs. This indicates the problem should be diagnosed as soon as possible. The ECM illuminates the CEL and SEL and stores a malfunction code if a potentially engine damaging fault is detected. These codes can be accessed in one of four ways:

Using the Diagnostic Data Reader (DDR)

Flashing the CEL and SEL with the Diagnostic Request Switch (may be combined with Stop Engine Override switch, see Figure 5-5)

Using the Detroit Diesel Diagnostic Link™ (DDDL) PC software package
By ProDriver®, Electronic Fire Commander™, Electronic Display Module (EDM), or other display

There are two types of diagnostic codes:

An active code - a fault present at the time when checking for codes
An inactive code - a fault which has previously occurred; inactive codes are logged into the ECM and time stamped with the following information:
First occurrence of each diagnostic code in engine hours
Last occurrence of each diagnostic code in engine hours
Total time in seconds that the diagnostic code was active

Diagnostic Request Switch
The Diagnostic Request Switch is used to activate the CEL/SEL to flash codes. Active codes are flashed on the SEL and inactive codes are flashed on the CEL (see Figure 5-6). Inactive codes are flashed in numerical order, active codes are flashed in the order received, most recent to least
recent. The Diagnostic Request Switch can also be used as the Stop Engine Override (SEO) Switch. The codes are flashed out of the ECM connected to the switch.

The Diagnostic Request Switch is used to flash codes in the following circumstances:

The engine is not running and ignition is ON
The engine is idling

In both circumstances, activating and holding the Diagnostic Request Switch will flash out the diagnostic codes.

Diagnostic Request Switch/Stop Engine Override

If no separate Diagnostic Request Switch is configured, the SEO Switch serves as both a Diagnostic Request Switch and an SEO Switch.

The Diagnostic Request/Stop Engine Override Switch is used to flash codes in the following circumstances:

The engine is not running and ignition is on
The engine is idling

In both circumstances, activating and releasing the switch will flash out the diagnostic codes; activating and releasing the switch a second time will stop the ECM from flashing the diagnostic codes. Codes will also cease flashing if the engine is no longer at idle. The codes are flashed out of the ECM connected to the switch.

Post the codes and we can go from there....

[luvrbus]

Electronics are not the only thing to keep that engine from running,check your fuel supply if it has no fuel pressure it will not run the injectors are not electronic injected they are manually injected.
And transits buses are famous for some type safety gizmo to prevent starting and drive a ways 


good luck

[Ace]

"the injectors are not electronic injected they are manually injected"

Not sure if I understand this or not or even if it's related but on mine, there is a fuse that powers the left bank and a fuse that powers the right bank. If one or both of these fuses blows, the engine will either run very badly or not all depending on if one or both fuses blow! This is a problem I encountered when one fuse blew and one side of the engine was cold where as one was hot. It would not accelerate but it would idle just fine!