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 IH 3800 no crank
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waverlybus
Senior Member

94 Posts

Posted - 07/13/2018 :  1:42:30 PM  Show Profile  Reply with Quote
what am I missing here, 1998 IH 3800 will not crank after sitting part of the summer. I can turn on the key and everything will turn on but it will not crank. solenoids behind switches seem to be working fine, replaced starter relay on bulkhead under hood, fuse in fuse box is good. no power to s-terminal when trying to crank, I can use a jumper button on the starter solenoid and get it to start with the key on no problem. Is there another relay or fuse I am missing. thanks

kummins
Active Member

41 Posts

Posted - 07/14/2018 :  10:07:08 AM  Show Profile  Visit kummins's Homepage  Reply with Quote
neutral safety switch, shift lever out of position, bad ignition switch, broken wire/bad connection on the 's' terminal/wire. fuse (40amp) in battery box ng

step on brake pedal while turning key. p-brake on.

if it's a manual trans, depress clutch pedal to start.
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eddo
Advanced Member

USA
311 Posts

Posted - 07/16/2018 :  09:22:08 AM  Show Profile  Reply with Quote
Voltage good?

My 1998 4700 has a starter relay attached to the main wire harness that goes down the left side of the engine. I had no idea it was a starter relay until it fried and wouldn't let the truck start.
I also have push button start buttons on the dash, do you?
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waverlybus
Senior Member

94 Posts

Posted - 07/16/2018 :  11:14:59 AM  Show Profile  Reply with Quote
It is in neutral, I tried all the other positions as well. Im going to try a different switch. voltage is good. fuse in the battery box is good. I don't see another relay in the harness jut the one on the fire wall which I replaced with no change. depressing brake pedal doesn't change anything. it is an automatic trans. no push button just key start. Thanks for the suggestions im going to trace my S terminal wire and see if I can find anything and I have another key switch I can try.
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eddo
Advanced Member

USA
311 Posts

Posted - 07/16/2018 :  11:28:11 AM  Show Profile  Reply with Quote
is your neutral safety switch working?
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waverlybus
Senior Member

94 Posts

Posted - 07/18/2018 :  12:25:37 PM  Show Profile  Reply with Quote
anyone know where the neutral safety switch is in a 3000 series Allison? It has a lever shifter
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aaronwilmoth80911
Top Member

538 Posts

Posted - 07/19/2018 :  12:12:14 PM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
Make sure all your interlocks are working properly. Had one before that the back door handle wasn't all the way down, but down enough to kill the buzzer but not down far enough to allow it to crank.
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waverlybus
Senior Member

94 Posts

Posted - 07/19/2018 :  12:44:07 PM  Show Profile  Reply with Quote
I think its too old for interlock. I can start the sister bus I have that is only one number different on vin# with the rear door open and all emergency exits open. I have traced the wires from the starter through the starter relay on the fire wall through the bulkhead connector to a relay in the drivers kick panel. I can jump power in the relay to the signal wire and the bus will start, there is supply voltage but no ground or power to the coil side of the relay. I traced those wires also, one goes to another relay and the other 97H wire (purple) goes up into the dash where I cannot trace it and cannot find the other end of it. frustrated and stuck.
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Rich Michels
Active Member

12 Posts

Posted - 07/19/2018 :  7:58:08 PM  Show Profile  Reply with Quote
I'm not sure on the 3800 bus version,,, on the truck version on the passenger side of the dash behind the panel is 3 relays. I believe there is one that has a yellow color base, this is a interlock / starter relay. It's been years since I've worked on one,,,,hope this helps.
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waverlybus
Senior Member

94 Posts

Posted - 07/20/2018 :  08:50:11 AM  Show Profile  Reply with Quote
I think I am going to bypass the second relay in the drivers kick panel. I temp wired it up bypassing it and it starts and runs like it should. Not sure what that relay is for though. It will still not start in gear but fires right up in neutral. could not find a yellow based interlock relay anywhere in the dash. I was able to finally trace the purple 97H wire from the unknown relay back out through the bulkhead connector and it seems to run down to the transmission. the other wire, red 17c wire seems to disappear into the harness where I cannot trace it without tearing the entire dash harness out and apart. if anyone has a schematic and can look at wire numbers I would be interested in knowing what they actually go to.
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waverlybus
Senior Member

94 Posts

Posted - 07/20/2018 :  08:57:39 AM  Show Profile  Reply with Quote
17c goes to the ign switch, and 97h must be a ground that goes somewhere, not sure where. so if I ground 97h it will start and run normally
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shawnmc005
New Member

1 Posts

Posted - 07/25/2018 :  03:58:01 AM  Show Profile  Visit shawnmc005's Homepage  Reply with Quote
Check the main power feeds for the computer straight from the batteries. They will corrode inside the wire loom and won't let the bus crank.
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