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daley
New Member
8 Posts |
 Posted - 06/03/2020 : 6:12:42 PM
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Hi there,
I have a 2001 Thomas Saf T Liner HDX
It has rear engine CAT 3126 and Allison Transmission.
I bought it to convert into a tiny home on wheels and the previous owner had already started this process.
All the interlock system seemed to have been removed and when I bought the bus it started no problem from the front and the rear.
Bus was in limp mode when I bought it, ie it had no power and wouldn't go over 20mph and definitely wouldn't go up a hill.
I had it put on a truck and brought to me. It was driven onto the truck.
When the truck arrived it would not start. All lights came on on dash but when you tried to crank nothing, no turn over nothing. Same from the rear starter switch.
We managed to jump start by getting power straight to the starter and I have been working on the inside for a while.
I recently thought it wise to try and start it, I have been charging the batteries regularly.
From the dash same deal, all lights come on but no crank, same from the rear starter switch.
I have figured out I can jump start it from a solenoid at the back of the rear electrical box by applying 12v to the terminal with wire which goes to the starter. It fired right up no problem after sitting six months and still does no problem.
I have obtained wiring diagram and been chasing wires to check for damage and I have tried to figure out the interlock system so that I can make sure it was removed correctly and not causing the problem but I wondered if anyone here that works on them might have any suggestions?
Where does the power to the rear start box come from? is it the ECU?
If it is ECU which circuits does that check for before allowing power from ignition?
Would CAT software/computer tell me about wiring issues or what might be causing the no start? I don't have it and cant really afford to get it but if it would be a big help I will try and get someone with it to come and plug it in.
Also, how does one attach wires to the deutsch round plug at the back box? two wires have come out and I cannot get them to stay in. The connector is pretty corroded with it being aluminum and old, I may well get a new one and transfer all the wires one at a time.
Sorry for all the questions and long first post but if any of you have any ideas, tips, pointers, insults, or otherwise I would love to hear from you as I really would like to get this thing started, its no big deal really but it would be kind of symbolic and help me feel better if I could figure it out.
Anyway, many thanks for reading, your time and any input you may have.
Daley
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Bluenozer
Top Member
Canada
644 Posts |
Posted - 06/04/2020 : 01:57:37 AM
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| cat software will not help you , not engine related if you can cross it over and the engine runs with no issues( interlock does not put it in limp mode), does the solenoid have ignition power when you go to crank? either 3 or 4 post on should 12v from batt., the other an exciter wire from ignition and then a cable going to starter, if no power on exciter at crank then it could be interlock or a fuse or broken wire |
OEM trained in wiring and all engine platforms for over 20 years
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daley
New Member
8 Posts |
Posted - 06/04/2020 : 6:22:22 PM
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Thank you for your input.
I am going to be working on this tomorrow.
I will test the solenoids activity with a multi meter and take notes.
I have been trying to trace the exciter wire by going through wiring diagram. The one at the solenoid is not the one coming out of the ignition, that's why I wondered if its going via the ecu. Hopefully tomorrow I can work out its route and see if it is broken anywhere or at least find out where the voltage stops when key is turned.
I just jumped it again today, engine fires right up but it takes a while to get to 1500-2000 rpm, that and how slow it is makes me suspect it is in limp mode, I suspect that is a different issue though to the electrical.
Thanks again for your help, I will be sure to report back what I find out. |
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Bluenozer
Top Member
Canada
644 Posts |
Posted - 06/05/2020 : 01:47:37 AM
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| pop the exhaust off the turbo and start it might have a collapsed catalytic (if equipped) this will cause slow rpm build and no power, system might have two body solenoids for starting system, never seen cat with with ignition wire pinned in it |
OEM trained in wiring and all engine platforms for over 20 years
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tigger2
Advanced Member
USA
470 Posts |
Posted - 06/05/2020 : 03:39:54 AM
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| The unit will not start from the front with the engine door open. to start from the rear you have to push the interlock switch small black button left upper rear of compartment and hold down while pushing the rear start switch with the key on up front. |
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daley
New Member
8 Posts |
Posted - 06/05/2020 : 11:05:00 AM
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Thanks again for all your help, it is very much appreciated.
I have been working around at the back electrical box and found a few things.
- The push button door open switch had some frayed wires, I have cleaned up the wires and reconnected it all. It shows to be working with continuity tester. I have tried to start with it pushed and not pushed and nothing happens.
- The rear ignition power flick switch has two orange wires going to it. I cleaned up corrosion and have found the switch seems to work with continuity test, however both poles show 12v when I put the multimeter on them, that doesn't seem right to me but maybe I am missing something? it seems like it makes the switch redundent, both poles have 12v even if switch is on or off.
- The push button start switch was corroded, I cleaned it up and it shows as working with continuity test and when pressed it closes circuit to let 12v through.
The 12v then goes to a bussman box of connectors and relays. It is from this box that the pink exciter wire that goes to the solenoid comes from.
It seems to me that something in the relay box is stopping the voltage going from the switch to the exciter wire.
I am going to take the bussman thing off after lunch and hopefully see the back/insides to see what pathways and relays supply the exciter wire.
As for the turbo, I have tried running it with exhaust off and it is still the same low rpm. I haven't looked yet but could the actuator not freely moving also cause it? or a vacuum leak?
My only experience of turbos and diesels is from vw tdi's and I have had these symptoms on happen from stuck actuator and vacuum leak, I haven't delved too deeply so not even sure the turbo works the same as tdi's.
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daley
New Member
8 Posts |
Posted - 06/06/2020 : 5:19:03 PM
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I fixed it!
I took the solenoid off to test it and found it wasn't triggering, I cleaned it up and wired it off the box, and it worked, so I don't know if it was just that or the ground also.
I will clean up all the grounds also, although I think I would like to redo the whole rear box, I will have to look out for a school bus junk yard!
Thanks for all your help, I am sure I will be back with more questions.
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tigger2
Advanced Member
USA
470 Posts |
Posted - 06/10/2020 : 10:48:38 AM
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| Great thanks for the follow up!! |
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2001 Thomas Saf T Liner HDX No Start Issue
