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Old 04-16-2020, 03:55 PM   #1
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Bus wonít start after air brake drain

Hey all,

My Thomas vista 3600 international (so many names!) has been sitting outside Austin for the past year or so as I worked on my conversion. I kept a trickle charger on the batteries but I didnít know that one should also empty the air brake tanks before storage. When I tried to start the bus the other day the engine purred beautifully but my air brakes wouldnít release. The bus just rocked back and forth a bit when I tried to accelerate but the wheels didnít turn at all. Pressing the air brake release button didnít seem to do anything. I was riding high off of successfully rerouting my exhaust out underneath the drivers side so in an attempt to diagnose the problem I casually flipped all the air tank valves and released all the air. I then tried to start the bus a minute after that but oh noooo it wouldnít start at all! I hear a click when I turn the key but thatís it. The air tanks are still completely empty, the brake press light turns on, and the fans/lights work.

Long story short: parked bus for a year and then emptying the air tanks caused the bus to not start

Any ideas? Iím @ https://www.instagram.com/yes_figuratively/ btw
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Old 04-16-2020, 04:41 PM   #2
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Is the transmission shifter in neutral?

As far as the brakes go, sometimes if it's sits for a while, the shoes will rust themselves to the drum. This will cause the issue you're experiencing.

As far as breaking it free, you typically release the brakes, chock the wheels, and then whack the drum with a sledge hammer. The shock from the whack will normally cause the shoes to brake free.

But you have to have air pressure first to do that. So make sure the transmission is in neutral and the batteries are in good shape.

I'd bet when you were rocking it trying to get out, you left it in gear, and that is why it won't start.
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Old 04-16-2020, 05:28 PM   #3
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I think this is a simple fix. I'm not sure the two are related, just a simple coincidence. Chock the wheels first and foremost. Clicking suggests the system is trying to energize the relay, but the circuit is not being completed somehow, which doesn't sound like it was left in gear, but still a possibility. First and foremost, check to ensure trans is in neutral, and if nothing changes, hammer on the starter, this sounds a bit like the starter has worn windings and has developed a dead spot, possibly a bad solenoid or bendix. It happens.

1) If hammering the starter doesn't wake it up... I highly doubt this, but the system may have a redundancy that locks out the starter if air pressure is low or bottomed out (not sure why, spring brake should engage below 20-40 psi anyway -- weird, but worth a look). If possible, see if you can adapt a fitting to the tank(s) to pressurize them and see if it fixes this. Otherwise, I'd go with the previous suggestion of the auto trans shifter not being in neutral, or perhaps a failed neutral safety switch. With a manual, you have to press the clutch fully, preferably with the trans in neutral. Any of this will lock out the starter.

2) Are any of these -- rear emergency door / entrance door / wheelchair lift door open? Any one of these could have a safety lockout.

If none of this wakes the starter, try checking your battery terminals and connections. Pour Coca-Cola or Dr. Pepper on the terminals -- I know it sounds crazy, but it cleans them of oxidation that can form between the posts/terminals and compromise the terminal connections. Could very well be all that's wrong.

The brakes sound easy. After sitting a while, the metallic brake shoes typical of commercial trucks and buses tend to rust to the drums. If the bus starts and can't break the rust loose on its own, get under there (wheels still chocked) with a hammer or rubber mallet and lightly tap the drum and shoe backing plate until they release.

LOL - Just saw that Booyah beat me to some of this... Gotta get up early in the morning, do I? LOL
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Old 04-16-2020, 07:23 PM   #4
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tried a lot of the suggestions

looks like I'm going to buy an adapter and try to put some air back in there manually. Seems like a long shot but it's all I've got at the moment. Thanks y'all!
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Old 04-16-2020, 07:59 PM   #5
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I've never seen a setup that wouldn't start even with Zero air pressure. How else is the system to build air pressure? (This doesn't apply to really old trucks with air starters).


Check your neutral safety. Did you leave it in gear by chance? It can happen to the best of us, especially if we're dealing with another problem.
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Old 04-16-2020, 08:08 PM   #6
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I've had brake shoes rust to the drum several times. I've had good luck pumping lots of water into the drum which loosens up the rust. It frees things up enough to get the shoes to let go.

I expect the no start and the brakes are not related.
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Old 04-16-2020, 08:28 PM   #7
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Quote:
Originally Posted by Brad_SwiftFur View Post
I've never seen a setup that wouldn't start even with Zero air pressure. How else is the system to build air pressure? (This doesn't apply to really old trucks with air starters).
Yeah, that's why it was just a wild-assed guess on my part, given the air spring's function in engaging the parking brake. It really wouldn't make sense (forgive me, I'm misfiring after sleeping 5 mins here and there for two days). I'm wondering if a solenoid wire may have burned, barely creating enough current to click.
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Old 04-16-2020, 09:53 PM   #8
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still no luck

Argh I tried to post earlier but I don't think it went through. I tested the solenoid and the battery voltage earlier and they're both good. Gonna investigate the possibility of the bus being stuck in neutral now as the air brake issue appears to be a separate problem. Thanks y'all! You know, this sucks and all, but I'm learning so much about the bus today that it's been a good experience... otherwise I'd just be bored watching Netflix in quarantine.
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Old 04-17-2020, 08:26 AM   #9
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You tested the starter solenoid? Or which solenoid did you test? And what did you test on it?

Checking if it's in neutral is easy, just look at the position of the shifter. I doubt you broke the cable, but in the process of rocking it, it is a possibility.
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Old 04-17-2020, 09:46 AM   #10
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Tests

I tested the starter solenoid with the ole screwdriver test- sparks shot everywhere so that doesnít appear to be the problem. The bus is in neutral and Iím about to see if I have a neutral safety switch on my at545. Maybe Iíll bang on the starter some more. Any other suggestions? Luckily Iím not going anywhere anytime soon
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Old 04-17-2020, 10:11 AM   #11
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So with the screwdriver test, did the engine bump over?

You are for sure jumping the terminals on the solenoid right? Someone on here recently, I forget who it was, had positive and negative battery lugs on their engine that they were jumping under the assumption it was the starter solenoid. Needless to say, in that scenario a lot of spark flew as well.
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Old 04-17-2020, 12:39 PM   #12
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Excellent question booyah! Maybe it wasnít the starter solenoid after all. I assumed it was Ďcause the click I heard when I turned the key seemed to be coming from the exterior wiring cabinet. The engine def didnít turn over, and upon closer examination that solenoid is attached to a fuse block that doesnít have anything labeled starter on it. Thereís a third wire attached to the solenoid (the black one in the photo) but Iím not sure what that goes to - it disappears into the wall of the electrical cabinet. When I ran a screwdriver across the + and that black wire nothing happened at all.

Photo Of cabinet solenoid: https://imgur.com/a/WcZOSGn
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Old 04-18-2020, 07:27 AM   #13
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The starter solenoid is under the bus by the starter motor. Those solenoids in the cabinet provide power for all of the auxiliary devices on the bus. That one in particular powers the fuse/breaker bar above it, as shown by the copper strap passing from the solenoid to the bar. It looks like the bottom nut on that solenoid, the one holding the red power wires, is loose. See if you can tighten it up and then leave it alone, it's not what you're after.
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Old 04-18-2020, 07:29 AM   #14
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Duplicate post
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Old 04-18-2020, 07:35 AM   #15
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The starter solenoid is the gold cylinder shown in the picture here.

The big lug at the top in that picture is the battery positive. The big lug an inch below that is the output to the starter motor. The big lug on the aluminum case is the ground.

And that's all if your bus uses a Delco starter, if it's equipped with a Mitsubishi starter it will look different.

Did you ever check that the shifter is in neutral
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Old 04-20-2020, 05:42 PM   #16
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updates

Ahh thanks for the diagram booyah! I climbed under the bus and learned a hell of a lot about my engine (considering I didn't know anything before). Found the starter and solenoid. I hooked up one lead from my multimeter to the battery + on the starter solenoid and the other lead to a clean bolt on the chassis and got a 12.5 or so - I don't recall the exact number. I took this to mean that I'm getting good power from the battery to the starter solenoid. I then checked for continuity/resistance between the body of the starter and the chassis with the multimeter and pulled a 0, which I took to mean it's grounded properly. Finally I used a screwdriver to connect the battery + on the solenoid to the output to the starter motor. I saw a fun spark show but the engine didn't turn over.

The shifter is def in neutral.

Maybe the starter went bad? I tried hitting it with a rubber mallet a few times again but that didn't help.
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Old 04-20-2020, 05:51 PM   #17
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Originally Posted by neuronmisfires View Post
Maybe the starter went bad? I tried hitting it with a rubber mallet a few times again but that didn't help.
12.5 is normal battery voltage.

You might want to look at this video (skip to the 10:45 range, which is when they started jumping things out -- they had trouble with the bendix until jumping out another wire at about 13:00).

Some starters and equipment are set up a little differently so that the typical screwdriver test won't necessarily work. These guys thought they had a bad bendix until they realized there was another wire that had to be jumped... But yes, a bad starter is still possible, though I would think it would have given trouble before now. I would thoroughly check the wiring connections at the starter, solenoid,and ignition switch to be sure nothing has come loose. Nuts can back off and compromise a connection that looks fine until you check the nuts for tightness.

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Old 04-20-2020, 06:53 PM   #18
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another update

Ahh I'll take a look at the video! I just hooked up a jumper cable from the starter negative to the battery negative to double check the ground but that didn't help. BUT when I hooked up a jumper cable from the battery + directly to the starter it finally made a sound like it was rotating but not engaging with the flywheel (or that's how my more mechanically inclined neighbor described it when he heard it). The engine still didn't start even when the key was turned though. By circumventing the starter solenoid did I skip something that would cause the starter to engage with the flywheel? If so, it looks like the solenoid is the problem!
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Old 04-20-2020, 07:36 PM   #19
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Originally Posted by neuronmisfires View Post
Ahh I'll take a look at the video! I just hooked up a jumper cable from the starter negative to the battery negative to double check the ground but that didn't help. BUT when I hooked up a jumper cable from the battery + directly to the starter it finally made a sound like it was rotating but not engaging with the flywheel (or that's how my more mechanically inclined neighbor described it when he heard it). The engine still didn't start even when the key was turned though. By circumventing the starter solenoid did I skip something that would cause the starter to engage with the flywheel? If so, it looks like the solenoid is the problem!
Quite simply, in cranking the engine, there are two forces at work. The starter motor rotates, but the bendix actually kicks the pinion gear out into the flywheel for cranking. Some starters do all this through the solenoid, but it appears that some starters (not all have the solenoid mounted integrally) require two completed circuits to fully engage, one circuit energizes the windings in the motor, the other engages the bendix, as shown on the grader in the video.

I cannot claim to know for sure if this is the case in your situation, but it is a possibility that should be carefully explored. If you hear the whirring of the motor running but the engine is not cranking over, your bendix is not engaging. In that situation, the motor can run all day and not actually be cranking the engine. Most will straighten out with a few whacks from a hammer or mallet, but if it's designed with the extra wire as shown in the video.

I guess some of these have everything running through the solenoid, and some of them simply use the solenoid as a relay for the bendix, while the starter has its own circuit? Just a thought.

I just ran across that video and thought it jived a bit with what you're experiencing. When you watch the video, you'll see what is going on, they show a shot of the extra wire they wound up jumping out, and then the engine cranked right up. Maybe Booyah can confirm or refute this. Seems to me it might point to the solenoid, but I wouldn't just replace it on say-so until bypassing the solenoid cranks the engine.
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Old 04-21-2020, 10:27 AM   #20
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Cheese wagon is right, on certain delco's the solenoid operates an internal lever that pushes the bendix out to the ring gear.

What you need to do, is grab your voltmeter and go under the bus. Have your neighbor/friend try and turn the key, and while they're turning it, see if you hear the solenoid knock.

If you do, have them hold it turned, and measure for voltage at the output terminal of the solenoid, the one between the solenoid and the motor.

If you don't, have them hold it turned, and measure for voltage at the little terminal on the solenoid.

Get back to use with what you find.

Jumping the two big terminals on the solenoid should get the starter motor turning. If it doesn't, you either have a dead spot in the motor, or a bad connection to it. With you using jumper cables from the battery to that solenoid, I'm wondering if the wiring or connectors might be corroded.
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