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Old 07-09-2020, 05:33 PM   #1
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No crank

Hi all Iím working on a 2010 international maxforce 7 with Allison trans, it started out no crank with electric fault in cluster. I found tcm harness broken repaired and fault went away, still no start, fires right away with power prob to starter relay, but at some point Iíve lost switch power to master disconnect. Iím lost and frustrated need help. Journeyman mechanic new to buses
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Old 07-09-2020, 06:07 PM   #2
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Do you have power to the ignition switch and if so do you have power out of the switch start terminal with key turned to start? Have you monkeyed with any of the safety switches like open door, kid asleep on the seat, neutral safety switch at tranny? Is there continuity between the start terminal on the ignition and the start relay?

You no doubt know about multiplex wiring. Just be real careful about probing with a hot wire source because what you think you see in the wiring may not be reflective of what is really happening with the wires.

I'll be interested to hear what you discover.
Jack
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Old 07-09-2020, 07:40 PM   #3
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are there still any codes in the cluster? typically an issue where manually powering the starter relay ends up being one of a couple things.


1. - the ECM isnt getting the Neutral signal from the transmission.. (does moving the shifter reflect in the gear display in the cluster? )


2. a faulty ignition switch - does turning the key to the start position cause any change? ie different lights in the cluster.. fans turn off, a click in the switch panel? this would indicate that the ignition switch is making contact in the start position


3. a Vandal-Lock system is active.. if your bus had any door locks for the emergency or wheelchair exit doors, having those locks locked will tell the ECM to disable the starter relay as all doors must be unlocked for the bus to start


4. any other codes set that you vcan read from the cluster? certain error codes related to the ECM will fail to energize the power or starter relay..


-Christopher
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Old 07-09-2020, 08:13 PM   #4
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The key switch has power going to it and power out to the respective poles, I can hear a relay clicking beside the master disconnect solenoid, there it no codes active in the unit, and when I put power to the disconnect I can test all the door alarms and they all work, not sure about the kid asleep.trans reads neutral in cluster,
Does the acc pole on key switch go directly to the master disconnect?
If not where does it go,
I will check contenuity From switch to relay in the am
Thanks for the replys
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Old 07-09-2020, 08:45 PM   #5
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Check and make sure your starter relay that you here clicking has power to terminal 30. May just need new starter relay.
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Old 07-10-2020, 09:57 AM   #6
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Yes I have continuity between ignition start and starter relay,

It’s not the starter relay that’s clicking,
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Old 07-10-2020, 10:10 AM   #7
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I get a similar clicking (actually a double click) from the glow plug relay with the spacing dependent on the pre start engine temp. I expect the first click is the actual glow plug relay and the second the injector relay.

What happens if, with the ignition on, you artificially apply power to the ignition start terminal?
Jack
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Old 07-10-2020, 10:38 AM   #8
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Nothing happens unless I jump the starter relay.
I still have to power to the master disconnect solenoid trigger
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