School Bus Fleet Magazine Forums
Home | Profile | Register | Active Topics | Members | Search | FAQ
 All Forums
 Professional Garage
 Enter Forum: Professional Garage
 2006 BB C7 CAT will not crank then randomly does
 New Topic  Reply to Topic
 Printer Friendly
Author Previous Topic Topic Next Topic  

familyman
Active Member

16 Posts

Posted - 08/03/2015 :  08:49:36 AM  Show Profile  Visit familyman's Homepage  Reply with Quote
I am working on a BB bus that will not crank and nothing happens when you turn the key on. If you leave the key on for a long period of time, it will eventually go through the startup checks and gauges will sweep. The bus will crank and start. However this is short lived and the bus dies. It does not seem to be affected by time. It can do this cycle in a relatively short period of time or take forever to duplicate. It seems that every time I start looking at the wiring chasing the powers and grounds it begins to work correctly and I cannot do any further testing. Any ideas would greatly be appreciated. I do know that the 2 solenoids in the electrical panel are not being energized when it doesn't crank. Thanks for any help!

Thomasbus24
Administrator

USA
4544 Posts

Posted - 08/03/2015 :  10:36:09 AM  Show Profile  Reply with Quote
Transit? Is so, there is something called a PDU (power distribution module) under the bus in front of the left front wheel. Whoever decided to put it there should be executed. Open it and see if its all corroded up. Pull the fuses and check the blades.
Go to Top of Page

familyman
Active Member

16 Posts

Posted - 08/03/2015 :  11:45:52 AM  Show Profile  Visit familyman's Homepage  Reply with Quote
It is a school bus, not sure if it would be built the same, but I will check.
Go to Top of Page

aaronwilmoth80911
Top Member

538 Posts

Posted - 08/03/2015 :  12:22:14 PM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
I think what Thomasbus24 is asking, is if it is a transit style school bus. Flat front with the engine in the front covered by the body or a rear engine bus, or if it is a conventional style school bus. This information will aid others in being able to help you.
Go to Top of Page

Thomasbus24
Administrator

USA
4544 Posts

Posted - 08/03/2015 :  6:05:08 PM  Show Profile  Reply with Quote
Yeah, sorry, that's what I meant.... conventional, flat nose and if no nose rear or front engine?
Go to Top of Page

familyman
Active Member

16 Posts

Posted - 08/04/2015 :  09:22:28 AM  Show Profile  Visit familyman's Homepage  Reply with Quote
Oh yes, I've got too many things I'm working on at once. It is a conventional style with hood and front fenders tilting forward. I looked at it this morning and it would not crank. I used the opportunity take do some testing.


In the first picture, I found that with key on I have B+ at 2,3,5 and 6. In the second picture, B+ was present only on #3 which is always B+ anyway. I have found that the ignition switch is also working as it should (grounding the proper circuits at the correct time). I also found that the ignition relay and ECM ignition relay are not getting the ignition feed on pin 86 to energize the relays. So now my question is where the ignition feed comes from. I do not have a wiring schematic for this. I am going to start tracing wires.
Go to Top of Page

aaronwilmoth80911
Top Member

538 Posts

Posted - 08/04/2015 :  10:54:23 AM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
What year is the bus? I have some manuals laying around that may be of some use.
Go to Top of Page

aaronwilmoth80911
Top Member

538 Posts

Posted - 08/04/2015 :  11:14:22 AM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
Sorry, I wasn't paying attention and didn't notice that you put the year in the title. Looking in the BB manual, that cluster of 3 relays in the first picture towards the top right, the middle one is titled as a "70 amp ignition solenoid" and the one to the right of it (smaller relay) is the ECM IGN relay. The 2 larger relays go down and to the left where you have the number "3" labeled in the picture. The smaller relay goes down and to the right to the area labeled as "4". Hope this helps. Let me know if you need more and I'll see what I can do.
Go to Top of Page

familyman
Active Member

16 Posts

Posted - 08/04/2015 :  2:24:52 PM  Show Profile  Visit familyman's Homepage  Reply with Quote
When you say they go to the 3 and the 4 are you referring to the power going through the relay or the power to operate the relay? I was able to test for awhile today. If I powered fuse block 4 and 6 with a jumper wire I was able to jumper the starter relay and get it to start. It still would not start with the switch. I know that the switch and the wiring to it are working as they are supposed to.
Go to Top of Page

aaronwilmoth80911
Top Member

538 Posts

Posted - 08/05/2015 :  09:03:39 AM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
The way it looks in the book is that 3 and 4 should be powering those relays. Sorry, I wrote that out a little ass backwards. Pin 30 on the IGN relay is BATT power and 87 is IGN power, 85 is IGN relay ground and 86 is labeled as "Ignition Dropout". Hope this helps a little more.
Go to Top of Page

familyman
Active Member

16 Posts

Posted - 09/02/2015 :  2:18:48 PM  Show Profile  Visit familyman's Homepage  Reply with Quote
so I am not 100% sure this is going to stay fixed but the ignition relay and ignition power relay have both been replaced and now all is working as it should. We will see how long it goes this time. Wrecker is on speed dial, lol
Go to Top of Page

familyman
Active Member

16 Posts

Posted - 09/25/2015 :  04:56:16 AM  Show Profile  Visit familyman's Homepage  Reply with Quote
Update to the ongoing saga, the bus would not start again. Number 5 in the first picture had a loose connection on the right hand post. Not sure how that wasn't caught before with all the wiggle tests that took place but it seems to have corrected the issue.
Go to Top of Page

Cal Mc
Advanced Member

303 Posts

Posted - 09/28/2015 :  8:52:27 PM  Show Profile  Visit Cal Mc's Homepage  Reply with Quote
Hopefully that will solve your problem. Good find and inexpensive fix.
The multiplex module in the first picture has caused us problems with the same symptoms. We have changed three of them now in the thirteen buses that have them, all for hit and miss no starts.
Go to Top of Page

bwest
Administrator

United States
3820 Posts

Posted - 09/29/2015 :  06:22:40 AM  Show Profile  Reply with Quote
quote:
Originally posted by Cal Mc

Hopefully that will solve your problem. Good find and inexpensive fix.
The multiplex module in the first picture has caused us problems with the same symptoms. We have changed three of them now in the thirteen buses that have them, all for hit and miss no starts.



.... and they cost a lot of money. lol

Bryan
Go to Top of Page

familyman
Active Member

16 Posts

Posted - 11/06/2015 :  12:27:48 PM  Show Profile  Visit familyman's Homepage  Reply with Quote
Update on the Gremlin bus for all those curious as to what is going on. This bus would not start again the other day and all the connections that were checked previously are good and I could find nothing wrong. As before, when I started to do some form of testing, it decided to miraculously heal itself. It is now at a local shop and they are pulling out their hair trying to get it fixed. They have had it for 2 weeks and not making any progress.
Go to Top of Page

Cal Mc
Advanced Member

303 Posts

Posted - 11/10/2015 :  7:04:16 PM  Show Profile  Visit Cal Mc's Homepage  Reply with Quote
We had one with a hit and miss no start. Every time we went out to look at it, the thing would not fail. We wired in a series of small indicator lights mounted in the dash. Indicators were lit by (1) the ignition switch input to the multiplex (2) output from the multiplex
(3) output from the starter relay that is above the multiplex.
We turned the bus loose with the driver with instructions to take note of which lights did not illuminate when the bus would not start.
Within a couple of days the problem was solved.
Go to Top of Page

Been Deleted
Active Member

USA
28 Posts

Posted - 11/22/2015 :  10:14:59 AM  Show Profile  Reply with Quote
I have 19 of the 2006 bb with c7s too. they all had similar problems. I fixed the problem buy running zip ties around the relays in the engine relay box, and then some needed a more heavy duty battery shut off switch. The contacts for the smaller ECM cable in the switch would burn and not make contact.
Go to Top of Page

familyman
Active Member

16 Posts

Posted - 12/18/2015 :  05:29:53 AM  Show Profile  Visit familyman's Homepage  Reply with Quote
I outsourced this bus as I did't have the time necessary to find the issue. The shop I sent it to said the module(#6) was faultly. They replaced it and rechecked. They are confident that it was the problem. Time will tell.
Go to Top of Page

Cal Mc
Advanced Member

303 Posts

Posted - 12/18/2015 :  11:13:12 PM  Show Profile  Visit Cal Mc's Homepage  Reply with Quote
That is the same module we had to change on multiple units. Other faults we have had with the same module include horn, signal and BU light circuits. When we had problems with the signal circuits we received instruction for our BB dealer to cut the wires out of the module and wire in relays to replace the module for the signal circuit. We were told at the same time to wire in the horn on an external relay because there had been "problems". We had problems with the BU light circuit and wired in a relay for that as well.
Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
 


School Bus Fleet Magazine Forums © 2022 School Bus Fleet Magazine Go To Top Of Page
This page was generated in 0.11 seconds. Snitz Forums 2000