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Author Topic: bus shutdown  (Read 995 times)
singing 4 Him
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« on: July 30, 2006, 04:52:13 PM »

Hey everybody, thanks for the info on the roof top instalation.  I've got a new question, our bus keeps shutting down. The hot engine low oil pressure lights come on and then the bus shutsdown.  Our oil pressure and water temp are fine.  Sometimes the bus will run for several miles just fine then shutdown.  Other times as soon as the air pressure is up enough to trip the fuel shut off it shuts down.  Is it most likely the sending units or the actual switch that controls the shut down.  I would appreciate any help also is there anyway to test either of these?    Thanks
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Hartley
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« Reply #1 on: July 30, 2006, 05:17:50 PM »

Some buses are equipped with a pressure switch on the secondary fuel filter that will cause the engine to shutdown
if the fuel pressure drops off. ( clogged primary filter or out of fuel ). Depending on how yours is wired for the shutdown
safety circuit it may trigger the HOT or OIL or even the air pressure alarms.

Look at your fuel filters and look for a pressure switch on top of one of them. get a jumper clip lead and jump the two
terminals together and start up to see if that was the problem. If it was not the problem then you will need to find
the 3-psi low oil pressure switch which is usually mounted on the same common oil distibution-bar with the pressure sender. Jump across that and see if that's the problem.

If it's not a fuel issue or oil pressure issue then start looking at the alarmstats mounted in the top radiator hose/thermostat
housing. There usually will be one alarm stat and one temperature sender. Some engines have 2 alarm stats ( one of each thermostat housing ) Most only have one. alarm stats usually are wired to a relay somewhere like in a junction box or rear
remote start panel. They short to ground when activated which operates a relay. Most are called RUN relay or SHUTDOWN
relay. Depends on what bus you have.

Good luck finding the problem... I could say more but there are others better qualified to help you from this point...

Dave....
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Stan
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« Reply #2 on: July 30, 2006, 05:24:02 PM »

First step in trouble shooting your problem would be to disconnect the high temperature shutdown sender and the low oil pressure shut down sender and then one at a time. This will tell you if one or both or neither is the problem. With that information I can give you more advice.
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Beatenbo
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« Reply #3 on: July 30, 2006, 07:48:44 PM »

Don't know what kind of bus, but I had a MCI 96A3 same problem. The 3 wires to your heat sender and alarmsat shut down (one in each head) croos the top of engine and down to a Junction block on MCI the wires can become chaffed and any times a bare spot hits metal it grounds and shuts down . Wiggled wire by accident one day and it shut down wiggled again and stared right up. Check tose 3 wires.
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JackConrad
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« Reply #4 on: July 31, 2006, 04:25:51 AM »

Sounds like a wire is grounding out somewhere or a bad sender. What is the make and model of your bus?  Someone may be able to tell you which terminal numbers in rear and front panels to disconnect to trouble shoot.  Disconnect alarmstats and low oil senders. If problem persisit it is a wire grounding out. If problem is not present, re-connect low oil sender and alarmstats one at a time to determine which one is faulty.  Jack
« Last Edit: July 31, 2006, 04:29:08 AM by JackConrad » Logged

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