Bus won’t start

[Tall_texan]

Hello everyone,

I have a 2006 Thomas bus with 5.9 Cummins that I purchased a little over one year ago. I am about half way complete with my conversation. I drive my bus almost every weekend to keep the batteries charged, etc. and it has always started right up with no issues. Now for some reason, when I turn the key one click to the right, the dash lights no longer light up and the fuel pump does not engage. If I turn the key one more click to the right, the starter will engage, however the engine will not start since it isn’t getting any fuel.

This issue seems to be intermittent. sometimes everything works and it starts right up and other times it doesn’t.

So far I replaced the fuel lift pump and the ignition and neither has resolved the issue. Any help or ideas would be greatly appreciated.

 

[ewo1]

I would start out by testing the ignition switch with on ohmeter.

 

[Timeline]

Try moving the shifter around a bit, hope it's something simple like the neutral safety switch needing a bump. My bus can randomly do that.

 

[Tall_texan]

I changed out the ignition switch yesterday thinking that might fix the problem but it is had no effect.

 

[BamaBus]

Not sure which Thomas you have. I don't think its any safety switch issue but you have lost power to the ecm side of things. Could have been ignition switch, but you replaced it. Wiring from switch to fuse panel? Check all related fuses in the electrical compartment and inline fuse (if applicable) in battery compartment. Post a good pic of the fuse/relay diagram in the electrical compartment under drivers window if possible. Assuming it's cranking but not starting.

 

[Tall_texan]

Thank you for the replay. I tried that as well with no positive results. It the past, when the shifter was not positioned correctly, the starter would not turn over at all. With my situation, the dash lights don’t come on, however my starter engages.

 

[magnakansas]

Tall texan

From your description of no instruments and you are able to activate the starter.

I would say you have lost power to the ecu. Find the wire that. Feeds power to the ecu and test for key on power. Do this at the ecu. If power, test further the operation of the ecu. If no power work backwards until you find voltage.

There may be a point where you have to have the bus towed in to a shop with more sophisticated test equipment. And knowledge.


William

 

[Nawbdy]

Make sure your batteries are carrying a full charge, 12.7 to 12.8. I've had a couple instances when my bus would turn over but not start. Twice it turned out that, even though the starter turned the engine over, (apparently) the ECM wasn't seeing a minimum voltage to enable starting.

BTW, my bus appears to have a separate circuit (wiring) for the ECM with power and ground coming off the batteries independent of the main battery connections. I say 'appears' because I haven't traced those 2 wires to their destination but I assume it's the ECM with possible stops elsewhere on the way.

 

[Tall_texan]

Thank you for the response. My ECU comes on when I turn the key one click to the right so I know it’s getting power. My batteries both have a good charge and the inline fuse near the batteries is good. The weird part is sometimes my dash lights come on and the engine starts up just fine. Other times, my dash lights do not come on but the starter will turn over. It just doesn’t start the engine. It’s got to a be a short somewhere.

Make sure your batteries are carrying a full charge, 12.7 to 12.8. I've had a couple instances when my bus would turn over but not start. Twice it turned out that, even though the starter turned the engine over, (apparently) the ECM wasn't seeing a minimum voltage to enable starting.

BTW, my bus appears to have a separate circuit (wiring) for the ECM with power and ground coming off the batteries independent of the main battery connections. I say 'appears' because I haven't traced those 2 wires to their destination but I assume it's the ECM with possible stops elsewhere on the way.

 

[Tall_texan]

Problem solved

With everyone’s help today, my problem is solved. The ECU was getting power when I turned the key on, however when I traced the power wire from the ignition to the ECU, I found a cut in the power wires insulation. The copper was almost cut in half. Once I repaired the wire, everything worked!

Thanks again for everyone’s help. I will sleep better tonight.

 

[HamSkoolie]

Pulling codes should be the FIRST step and yet no one mentioned it.
The corrective action indicates that the ECM was getting voltage but not the specified voltage required for it to enable the injectors.
That would have thrown a code which would have identified the cut wire before spending time and money throwing parts at the problem (and likely tools and such at the floor when frustrated...LOL).