DDEC Issue again...

[Sebulba]

The year model of the MCI has a setting to produce more HP and torque on cruise control you should use it as much as possiable for better performance and fuel milage with the cruise on you go from 430 hp to 470 hp

Wow! That's amazing.  If everything goes ok, the next time we start I will turn on the cruise and give it a try.

We are at 7300 feet, and I do notice less power up here, but still very respectable.

Thanks a lot

Seb

[Sebulba]

Well, some good news, I turned on the main power and all looks right.  I didn't fire her up so cr it 25 degrees out and I wasn't plugged in.

But, who knows, maybe I solved it. 🤔

Seb

[windtrader]

where you at Seb? Not so many roads for buses at over 7k

[luvrbus]

where you at Seb? Not so many roads for buses at over 7k

Says he is in Santa Fe NM that area is over 7000ft and fairly easy to get around in a bus there unless you are driving a N/A 8v71

[dtcerrato]

Says he is in Santa Fe NM that area is over 7000ft and fairly easy to get around in a bus there unless you are driving a N/A 8v71

Heck we've driven our NA 671 w/o Jake's with toad in Santa Fe & lots of high elevation Rocky Mountain area. No problem, just do it slower, again no problem. Just saying.

[luvrbus]

Heck we've driven our NA 671 w/o Jake's with toad in Santa Fe & lots of high elevation Rocky Mountain area. No problem, just do it slower, again no problem. Just saying.

Some of the 12% grades you don't pull off in a scenic view area and expect to get roiling again btdt with a 8v71 and 4 speed manual transmission but not in a lite weight 35 ft GM bus it was 40 ft converted bus 

[dtcerrato]

10-4 on pulling off on an uphill 12% grade. If & when we ever did due to extenuating circumstances, the four down dingy toad gave us the goose we needed to get moving again.although wifey never liked that drill she was a real trooper - the good kind not the red nor blue lights trying to pull us over for what we were doing. Lol 

[luvrbus]

10-4 on pulling off on an uphill 12% grade. If & when we ever did due to extenuating circumstances, the four down dingy toad gave us the goose we needed to get moving again.although wifey never liked that drill she was a real trooper - the good kind not the red nor blue lights trying to pull us over for what we were doing. Lol 

Wifes are troopers being a tight @$# I ran out of fuel trying to find cheaper fuel,I put the Jeep in 4 wheel drive and low range and Sonja pushed me 28 miles to Well NV lol of course she had something to say about me running out of fuel when we reached the Flying J

[chessie4905]

Haha, yeah, it happens. Years ago, I ran a 75 Honda Civic out of gas. Walked a mile to a grocery store. (no gas stations for another 5 miles.) Bought a gallon of Coleman lantern fuel and poured into the car. It ran but knocked a lot and rough, but got us to a station.

[Sebulba]

These are all great stories.  It's the real world.

Seb

[RichardEntrekin]

Let me make a suggestion, and explain the logic behind it.

You have checked most of the intermediate path to provide power to the ECM.
Seeing somewhat of a correlation between the NO CEL or SEL lights and other electrical anomalies up front could indicate that either the ignition switch or probably a relay triggered by the switch to turn on 12V electrical power to ignition circuits is not functioning properly.

The next time you turn the key and do not get the CEL or SEL lights, leave the key on. Go to the back and remove both plugs from the right side of the DDEC. Your manual has already instructed you how to check power on the power plug (the upper five pin one). But the DDEC also requires power on one terminal on the 30 pin plug to actually tell the engine to fire. Your manual should show you which one. If it's not in the manual, I will dig through my files and find it for you. EDIT: I found the info in an old post of mine about a similar problem On the 30 pin connector, B3, second row from bottom, pink wire, should also show 12V.

The point is that you REALLY need to determine IF the DDEC has power when you get this condition. If it does, you have a DDEC problem, if it does not you have a problem with voltage getting to the DDEC.

I would find the master Igniton power relay that gets an input from the key switch. You have to have one. There is no way the current for all the 12V ignition powered circuits goes through the key switch. When you find that relay, check the input side to see if the key on is providing a 12V trigger. And check the output side to see if the relay is actually providing 12V power to the ignition circuits.

[Sebulba]

Let me make a suggestion, and explain the logic behind it.

You have checked most of the intermediate path to provide power to the ECM.
Seeing somewhat of a correlation between the NO CEL or SEL lights and other electrical anomalies up front could indicate that either the ignition switch or probably a relay triggered by the switch to turn on 12V electrical power to ignition circuits is not functioning properly.

The next time you turn the key and do not get the CEL or SEL lights, leave the key on. Go to the back and remove both plugs from the right side of the DDEC. Your manual has already instructed you how to check power on the power plug (the upper five pin one). But the DDEC also requires power on one terminal on the 30 pin plug to actually tell the engine to fire. Your manual should show you which one. If it's not in the manual, I will dig through my files and find it for you. EDIT: I found the info in an old post of mine about a similar problem On the 30 pin connector, B3, second row from bottom, pink wire, should also show 12V.

The point is that you REALLY need to determine IF the DDEC has power when you get this condition. If it does, you have a DDEC problem, if it does not you have a problem with voltage getting to the DDEC.

I would find the master Igniton power relay that gets an input from the key switch. You have to have one. There is no way the current for all the 12V ignition powered circuits goes through the key switch. When you find that relay, check the input side to see if the key on is providing a 12V trigger. And check the output side to see if the relay is actually providing 12V power to the ignition circuits.

That all makes sense.  Let me see what happens the next few days.

I am planning to start it today, just to see if it all works, and tomorrow we plan to head to Albuquerque.

Thanks

Seb

[Sebulba]

Hello all,

Well, yesterday I started her without a hitch and the same today -- made it to Albuquerque with everything behaving as normal.

I don't know if we fixed it or it's just behaving better, we'll see in about 2 weeks when we head back to Albuquerque for tax season.

Thank you so much for your help.  The troubleshooting guide was great.

Seb