MY BUS STOPPED RUNNING! any suggestions

Beatenbo · September 19, 2008, 08:39:59 PM

If you remove the air shut down and a 2 stroke does not start it is a fuel problem You can drive it around the world with it disconnected. I owned 10 buses 5, GMs If it doesn't start after 10 sec it's getting air or not getting fuel or lost prime .

chriss · September 20, 2008, 10:01:25 AM

Quote from: Beatenbo on September 19, 2008, 08:39:59 PM
If you remove the air shut down and a 2 stroke does not start it is a fuel problem You can drive it around the world with it disconnected. I owned 10 buses 5, GMs If it doesn't start after 10 sec it's getting air or not getting fuel or lost prime .

thanks, I'll check out jjrbus' suggestion first to be sure that there is nothing seriously wrong, and if everything there is fine, then I'll disconnect it and try troubleshooting it from there.

Chris

gus · September 20, 2008, 07:50:05 PM

Chriss,

Some GMs have a shutdown switch on the rear panel. There are usually four switches, the second one from the right facing the engine is the "Run" switch. If this is accidentally hit (Easy to do) it will run until air pressure builds up and stop. I know all about how this works!! It does the same thing as leaving the front switch "Off".

chriss · September 21, 2008, 06:49:47 PM

Quote from: gus on September 20, 2008, 07:50:05 PM
Chriss,

Some GMs have a shutdown switch on the rear panel. There are usually four switches, the second one from the right facing the engine is the "Run" switch. If this is accidentally hit (Easy to do) it will run until air pressure builds up and stop. I know all about how this works!! It does the same thing as leaving the front switch "Off".

thanks for the suggestion, I did check it today and the switch was not on.
I think it might be a sensor, because I disconected the valve that shuts the engine down, and the bus ran just fine. I also made sure the coolant and
oil levels were ok. which they were.
now i need to check down the line to see which sensor or valve is bad.
thanks
chris

jjrbus · September 21, 2008, 07:04:49 PM

[/quote]
I also made sure the coolant and
oil levels were ok. which they were.
now i need to check down the line to see which sensor or valve is bad.
thanks
chris
[/quote]

When you say you checked the oil level, you mean oil pressure? You can have plenty of oil, but if the pump is bad you will have no pressure. But you knew that right! Jim

gumpy · September 21, 2008, 07:24:54 PM

Quote from: jjrbus on September 21, 2008, 07:04:49 PM

When you say you checked the oil level, you mean oil pressure? You can have plenty of oil, but if the pump is bad you will have no pressure. But you knew that right! Jim

Again, Jim is absolutely correct. The sensor is on pressure, not level.

chriss · September 21, 2008, 08:03:54 PM

Quote from: gumpy on September 21, 2008, 07:24:54 PM
Quote from: jjrbus on September 21, 2008, 07:04:49 PM

When you say you checked the oil level, you mean oil pressure? You can have plenty of oil, but if the pump is bad you will have no pressure. But you knew that right! Jim

Again, Jim is absolutely correct. The sensor is on pressure, not level.

I only checked the levels, but the oil pressure gage on the dash reads like it normally does while running, but the guage could be wrong. the other guage on the back above the engine has been broken for years. is there another way to check pressure besides the gauge?
chris

Dreamscape · September 21, 2008, 08:09:55 PM

Go out and buy a mechanical gauge! You will not correct the problem until you know for sure what your pressure is. They aren't that much. Heck even go to NAPA, Auto Zone or any parts place.

Paul

luvrbus · September 21, 2008, 08:17:52 PM

If he didn't have oil pressure as much as he has started the engine it would be a basket case by now

Busted Knuckle · September 21, 2008, 08:21:20 PM

Quote from: luvrbus on September 21, 2008, 08:17:52 PM
If he didn't have oil pressure as much as he has started the engine it would be a basket case by now

Well as usual Clifford you are correct! But at the same time I was once told it only took 2.5 lbs to make a DDEC unit happy! So it is possible to have VERY LOW pressure that may not be enough for the conventional low pressure switch! FWIW

BK

chriss · September 21, 2008, 08:50:28 PM

Quote from: Dreamscape on September 21, 2008, 08:09:55 PM
Go out and buy a mechanical gauge! You will not correct the problem until you know for sure what your pressure is. They aren't that much. Heck even go to NAPA, Auto Zone or iany parts place.

Paul

paul,
good point, i'll get a guage and double check to be sure.
thanks,chris

Dreamscape · September 21, 2008, 08:54:32 PM

Chris,

I just like the mechanical gauge to check, I always go by that when I fire mine up and then compare the reading to the electrical one on the dash.

Good Luck,

Paul

gumpy · September 22, 2008, 04:29:10 AM

Quote from: luvrbus on September 21, 2008, 08:17:52 PM
If he didn't have oil pressure as much as he has started the engine it would be a basket case by now

No need to scare the guy.

He said his dash gauge is reading normal as it always has. More than likely, that means that he has not lost oil pressure.

Yes, he replace the mechanical gauge in the engine compartment. But it still sounds like a sensor in the safety shutdown system is causing the problem. I'd start with the temp sensors. They're easy to get to.

craig

luvrbus · September 22, 2008, 06:47:38 AM

wasn't my intention to scare the guy gumpy the low oil pressure sensor on the shutdown on a Detroit 2 stroke very seldom goes bad or work when they idle hot some will read O on the the gauge that is why the rpm on idle is so important on these engines I've seen them idling at 300 or 400 rpm with no oil pressure showing and not shutdown fwiw

gus · September 22, 2008, 02:53:20 PM

My 4104 has a mechanical oil press gage installed back on the engine. I'm positive this was the way it was built because there are references to it in the MM and I assumed that all buses have them??

Presumably it was installed there for the use of mechanics working on the engine since there are starter and run switches there also.