HELP my bus won't start.

[somewhereinusa]

These are words I see way too often, usually from nu bees and it just isn't necessary. Often followed by "I took out all of the xxxx wiring and now it won't start". Often it's after taking out the door and hatch switches.

Just a little background, I was an electrical troubleshooter on ground equipment in the Navy, had my own import repair shop in the 70s, worked at a restoration/import repair shop where I did most of the electrical work. Some of the more memorable were Lamborghini ( all the wires were the same color, no wiring diagram) Porsche,( tiny wires with a relay on pretty much every circuit, short in one of their molded plugs caused main harness to melt together) 29 Ford (complete rewire for "fail safe" Great American race) on the rare occasions that I had a wiring diagram I had to translate to English. Thankfully that was just colors. Granted this was all pre computer.

For those who don't have any electrical experience and don't understand electrical diagrams. If you want to disable the door switches. UNHOOK ONE AT A TIME and see if the bus will start. For the most part a door switch is normally open meaning that when the door is open the switch is open meaning the circuit is not complete. If the bus won't start after unhooking a switch tie the wires together and see if that works. If you want to completely remove the wiring for some reason. Locate the other end of the wires ONE CIRCUIT AT A TIME and do there whatever you did to them at the switch end to make the bus start. Check to see if the bus still starts, if so it is now safe to remove the wires.

"The engine turns over/cranks but still won't start so I replaced the batteries and it still won't start" Really? I've read this a few times in the last few months. I believe that one even said a dealer told him to do that. IF AN ENGINE CRANKS AT A REASONABLE SPEED THE BATTERIES ARE NOT BAD, don't go buy new ones.

The very first thing I would do is go to the starter and energize the solenoid. (make sure trans is in neutral and brakes set, chock wheels). If the engine turns over at a reasonable speed, starter is good, batteries are good and battery cables are good. (You should clean them anyway). Now, put a test light on solenoid energize wire and turn key to start position, it probably won't light.

If it cranks/turns over but won't start. Go to the unit that is supposed to get power when the key is "on", on pre computer models, probably the fuel cut off, post computer probably ecu.

I usually work backwards from what is "supposed to work"

With the exception of the rear engine buses a school bus is a truck with different body on it. The main chassis wiring came from the manufacturer of the truck part, IE, Freightliner, International, etc. The bus manufacturer has added the interlock bits to the original wiring. The newer one were probably ordered with plug "123xyz" so that bus manufacturer can simply plug into it and have everything work.

Dick

[mmoore6856]

dont you wish they would read this before cutting wires?

[Mountain Gnome]

"The engine turns over/cranks but still won't start so I replaced the batteries and it still won't start" Really? I've read this a few times in the last few months. I believe that one even said a dealer told him to do that. IF AN ENGINE CRANKS AT A REASONABLE SPEED THE BATTERIES ARE NOT BAD, don't go buy new ones.

As an auto tech with over 20 years' experience, I disagree, when dealing with computer controlled motors. That might be true in the 1970's.

If the battery has one weak cell, its voltage may drop below 10V while cranking, even though the motor spins fine. The low voltage confuses the computer, or won't allow it to work at all, on some vehicles. Check the voltage at the battery with a voltmeter while cranking.

Many a vehicle I have seen have this problem. A new battery fixes it. Just don't confuse it with a lame alternator. Then just give your battery a good charge, and install a new alternator. My bus wouldn't start in cold weather with one, new, 810CCA battery. It spun just fine., but the voltage was dropping. Two connected in parallel, and it is OK, and starts immediately.

[Defjr333]

Maybe a sticky titled "Read B4 disconnecting door buzzer/ interlocks" then those posting that question could just be given link to that thread to create a nicemoment.
And fixes/ discussion for that issue will all be in one place instead of searching thru builds/ threads for one persons fix.
Doug

[cadillackid]

Originally Posted by Mountain Gnome

As an auto tech with over 20 years' experience, I disagree, when dealing with computer controlled motors. That might be true in the 1970's.

If the battery has one weak cell, its voltage may drop below 10V while cranking, even though the motor spins fine. The low voltage confuses the computer, or won't allow it to work at all, on some vehicles. Check the voltage at the battery with a voltmeter while cranking.

Many a vehicle I have seen have this problem. A new battery fixes it. Just don't confuse it with a lame alternator. Then just give your battery a good charge, and install a new alternator. My bus wouldn't start in cold weather with one, new, 810CCA battery. It spun just fine., but the voltage was dropping. Two connected in parallel, and it is OK, and starts immediately.

some navistar engines have a minimum RPM reading required to start the engine... I think a 444E is 160 and above (ill have to verify that in the book).. so just because it spins doesnt mean it will start.. weak or discharged batteries show themselves in many mysterious ways on these electronic engines..

-Christopher

[Robin97396]

Interlock issues are a certain constant on this sight. There is no one size fits all fix. Many of us have the interlock to thank for a painful educational experience to varying degrees.

Like others here I also have learned to appreciate the buzzer when I occasionally forget to latch a door properly, usually when I'm fatigued.

You're not the first person to want to hack out all that wire. We all feel your pain on this subject.

[cadillackid]

in my opinion, save the WIRE even if the circuit gets disconnected... when i took out a wheelchair lift I save the Wires.. sure made it easy when i wanted to hook up an auxilliary light .. I didnt have to run a wire all through the bus... the exsting wire was a nice 12 gauge.. toned it to the switch panel and bam.. easy for a light.
-Christopher

[Here to learn]

As i am learning this lesson the hard way right now, one of the big things that would have helped me is if i labeled each wire as i took a dome light off or unplugged a window or escape hatch. Take note of every wire, its color and the number printed on the wire itself and what it went to. Its too easy to get overwhelmed with the number of things that have wires going to them and confuse a dome light wire for a window or hatch wire. (for my vehicle the emergency windows, hatches and rear door interlock wires were all pink wires and so far they were the only pink wires. )

The interlock for those new to buses is a way of disabling the starter on a vehicle is one of the emergency windows or a hatch is open to ensure the safety of children. Disable these at your own risk and please make sure that your children are safe.

For my vehicle the interlock was in the form of an old starter solenoid with ground supplied to the center post from the rear door switch. I bypassed it by removing the two outer wire and joining them together.

An example of the solenoid is here https://www.macsautoparts.com/ford_m...passenger.html

A way to test it is to use a test light like this one https://www.autozone.com/test-scan-a...ter/186543_0_0

youtube instructions on how to use it if you never have. basically if you plug the end of the test light to the positive of the battery and touch a grounded circuit, the testlight bulb with light up as a bulb only needs power and ground and you are already supplying the power. This also works in reverse, if you clamp onto ground and touch a power circuit, it will light up. Test the center post to ensure it is getting ground. If not, thats why your bus isn't starting. Close the rear door, test the ground at the rear door, repair any cuts you made in the wire going from the solenoid to the rear door, etc. as long as you have ground on the center post of the solenoid, test for power on both sides of the solenoid. There is a direction of flow, meaning when you turn the key to start, one side of the solenoid should be getting power. As long as ground is present on the center post, the solenoid will connect the outer posts and allow power to go to the other wire. This can be bypassed by pulling the outer wires off and connecting them together. If you would like, they can be shortened quite a bit by tracing them back.

The buzzer for my bus was a simple matter of removing the pink wires from the one side and removing then joining the three black wires together from the other side.

[Robin97396]

I took a different approach on my first bus. I found my framing hammer and pounded the buzzer until it didn't buzz anymore. The interlock system worked silently.

I don't disable the interlock system any more. There's been a couple times when it stopped me from a mistake.

You're actually making progress, so kudos.

[Here to learn]

I think i like your method with the framing hammer better, gotta try that next time.

[Defjr333]

Ex Aviation Electronics Tech......if i dont have a schematic, i research the cr@p outta it 1st, then check everything works every 2nd circuit it disconnect to make it easier to "undo" my "brilliant" ideas.

[golfersmurf57]

First off throw away all the meters. Goto the local auto parts store and buy yourself a 12 V test light and a couple heavy duty jumper wires with alligator clips that's all u need to trace your circuitry if the fuse panel is labeled start there if not start with in switch and verify voltage then trace to fuse panel then emergency doors in and out then starter relay. Finally starter solenoid energize terminal. Or you could find the start terminal at the key switch and jumper directly to starter relay or add a small starter solenoid for a relay and wire it directly to the starter solenoid. Large (diesel) solenoids draw too much current for the ign switch to carry. Also an interlock system can interrupt the circuit using lower currents requiring cost effective cheaper switches for the coil circuit of a relay versus the solenoid. A schematic would give you a better way. Have you tried the manufacturer's site? Its also possible a local shop may be able to access the prints through Mitchell or Alldata.

Sent from my LGL64VL using Tapatalk

[Barkythebigfatdog]

Originally Posted by mmoore6856

dont you wish they would read this before cutting wires?

Hey we cut the wires to the interlock that was attached to the double door. Should we follow those wire to the ignition interlock and disconnect or should we go down another route? Would really appreciate any help possible!

[o1marc]

Originally Posted by Barkythebigfatdog

Hey we cut the wires to the interlock that was attached to the double door. Should we follow those wire to the ignition interlock and disconnect or should we go down another route? Would really appreciate any help possible!

If you've removed the interlock and the 2 wires going to it are unattached and the bus starts and runs, they can be deleted. Unless they can be repurposed in their existing location.

[BusLife4eva]

I went to start my bus (1999 International 3800 Amtran DT466E) with the emergency door open. (oops) The buzzer went off and obviously wouldn't start. I closed the doors and hatches and it still won't start. All it does is click at the solenoid in the drivers side access panel. I have charged the batteries, replaced the solenoid with two different units. Still nothing. There are no buzzers going off, the warn engine light comes on with the key and then goes out as normal. All of the fuses are good and I don't seem to be getting any power at the starter. I am at a loss here and don't know what else to do. Any help would be greatly appreciated!

I have included some pictures showing the solenoid in question. (It's the one with the brown-ish label)

I have only removed the seats and prior to this the bus started right up every time.

[musigenesis]

Do you have a barrel lock (aka deadbolt) on your exit door? My bus sometimes won't start (like just today, as it turns out) and I slam the barrel lock in and out a few times to make sure it's open and completing the interlock circuit. I really need to delete the damn thing but I have enough other electrical issues to worry about.

[BusLife4eva]

Originally Posted by musigenesis

Do you have a barrel lock (aka deadbolt) on your exit door? My bus sometimes won't start (like just today, as it turns out) and I slam the barrel lock in and out a few times to make sure it's open and completing the interlock circuit. I really need to delete the damn thing but I have enough other electrical issues to worry about.

No barrel locks on this bus.

[Eneldo4444]

Man I really wish I wouldve read this before I made a huge mistake... Now I feel like I am making it worse trying to figure out this electrical mess...

[RebekahZ]

Hi!

I won't lie - the mechanics and electrical aspects of the bus make me nervous. I'm dyslexic and numbers and mechanical things have never been my forte, but I can usually get around auto things well enough.

My bus was starting just fine after I cut wires, and then I didn't start it for a few weeks (I know, I know) and then it would sputter and not turn on. Now it's just not turning on.

This makes me think it's the batteries, because it WAS starting and then it was sputtering and then it died. There are two batteries under the driver's side, but they seem to be secured by metal rods.

I was told I could take them to Walmart to get them recharged, but I don't know how to disconnect or pull them out. Again, terrified of the mechanics and ruining something.

I'm converting by myself in upstate New York so my resources are limited to this forum, any help is so greatly appreciated!

[imxdemetri]

I hate that I'm adding to this. Should've done the research but long and behold I am now a member of Team "won't start". Had a mechanic come that I can confirm had no idea what he was doing- said I needed to reset my ECU and unplugged some other stuff. Mainly around the batteries. I can no longer reach him.



The bus: 2008 GMC Savana 3500 6.6 Duramax Cutaway Thomas build.


We gutted it. Saw the 1000s wires- decided without reading they must've just been for the heat, A/C, lights, and speakers...Ripped them all out.


The main panel or fuses and relays for every wire was located above the drivers seat.


They came from a black tube coming from the ground right behind the drivers seat.


Here are a few pictures of what was, and what now is and a list of what every wire says on it.
The pic next to the amazon envelope is where the black tube is right behind the drivers seat. The pic of all the wires is.....all the wires.
The pic of the panel is before I cut everything. I also took note of what most of what was hooked up to each relay.
I thought worst case scenario- the wires hooked up to the fuse need power...Take everything that isn't a ground- apply power. Ground the grounds..should be good? I haven't tried that- but those are my thoughts.



Please someone point me in the right direction.
1 yellow spare e 1 tan child Ck 1 tan dome lt 2 thick red vandalock 1 red pilot 1 green flash sw 23c 3 no label yellow 1 brwn marker lt 1 grey master 3a 1 yellow amber sw 1 green eight turn 1 green spare o 1 blue step light 1 blue a/c 1 blue cross gate 1 orange ac comp 3 red ignition 1 red htr hi 1 green htr low 1 purple ignition relay 1 red stop arm pwr 1 orange pilot


In addition, my batteries on the side of the bus died. I took them out to charge. When I replace them I parralleled them, hooked up the ground to the ground and the red positive to the positive. Upon further investigation- there appears to be 2 red wires that need to be hooked up. 1 already had a source of power going to it. Not sure where from since the bus was not running. There is a battery under the hood- but why would it be providing power to the other 2? picture of battery tray with the 3 connecting wires



In addition x2. After investigating the battery under the hood I noticed the grounding wire had this little attachment on it as if something else should be grounded, I could not find a loose male wire anywhere.- picture with yellow piece coming from battery connecting wire