Bus starts, runs for 30 seconds then quits

Sharkbait · December 14, 2015, 02:39:01 PM

Okay here's what happened. Bus was running great a week ago after not being run for about 6-7 years. I put 20 gals of fuel in it, sorted out the injector's issue then moved the bus from gravel to asphault. On the way I lost what I thought was an airbag. Jacked the bus up, airbags looked fine, found I had a break in the airline, fixed that. While the back of the bus was jacked up I thought I'd change the coolant since I figured it was easier to get a bottle under the radiator drain. Last step in changing the coolant is run the engine up to operating temp. Hold the circulation pump switch for 1 min. Then top off the coolant. The bus started and ran for about a min. Then stopped. I figure with the bus jacked up, all the fuel ran to the front of the tank and it starved it. I leveled the bus, added 20 more gals of fuel filled up the filters then tried to start it. Ran for 30 secs. I've been reading Rj's thread about adding an electric pump for just this occasion so I went to NAPA, bought a pump and installed it just before the primary filter. Same results only I notice that when running the fuel pressure gauge at the back of the engine starts creeping up from zero to about 10 psi before the engine stalls. I just changed filters about a month ago but can it be that I need to change them again? What else could be causing this? Thanks guys, Phil

Sharkbait · December 14, 2015, 02:58:23 PM

One thing I forgot to mention, when the bus stalls, I check the fuel filters, the primary one is full (probably because of the electric pump) but the secondary is low about an inch.

gumpy · December 14, 2015, 03:38:00 PM

it's overheating. You have an air bubble in your coolant system. That's assuming that bus has a safety shutdown.

Or, it could be the fuel.

If it were a MCI, it would be the stop/run switch in the wrong position.

eagle19952 · December 14, 2015, 04:15:03 PM

low coolant level sender dry... ?

Sharkbait · December 14, 2015, 05:10:33 PM

Okay next question, how do you clear an air bubble in your coolant system? And yes it appears I have a overheat sending unit.

eagle19952 · December 14, 2015, 06:03:18 PM

bleed bleed and bleed some more.. $:-\$

Sharkbait · December 15, 2015, 03:38:12 AM

I can see how an overheat sending unit can give me a alarm but how does it shut down the motor? When the motor shuts itself off now, the shut-off solonoid is not activated.

luvrbus · December 15, 2015, 04:30:40 AM

It is a fuel problem if it's been setting for a long period of time you may need to change the filters more than once then it could also be the fuel pump.Install a pressure a gauge on the secondary filter it should read around 30 lbs at idle and up to 65 or 70 lbs over 1/2 throttle

good luck

Sharkbait · December 15, 2015, 12:03:20 PM

Thanks all, it was the filters. Changed both, bled the air and saw the fuel pressure go up. Now for the next issue but, that will be a new topic. Phil

gumpy · December 15, 2015, 12:08:28 PM

Glad you got it. That whole shut-off solenoid piece would have affected my answer considerably.

OneLapper · December 16, 2015, 02:07:39 PM

Whoa Sharkbait!

Bleeding the cooling system on the 4106 is a bear! Without fail, it takes three heating cycles to burb/purge/expel the air from the coolant system IF you have the OTR heater still intact. Each time I drain the system, it takes a really long time to get the all the air out. It'll run hot until it's all out.

My bus won't shut down on overheat, but it was an option on the 4106.