Bus started then stopped running this morning ...wont start now

[RickB]

Dave, I think you said you have an MCI 7 and I'm not sure if this applies to you but on most non electronic MCI 9's we have an emergency shutdown that is basically a "flapper" to prevent your engine from getting the air it needs for combustion in the rare case of a runaway engine. If you have it you may have bumped it and it could be shut. It is spring loaded (think mousetrap here) mounted on the air horn on top of the blower and can be reset easily. Just a thought.

Rick

[Dlsnow]

Rick-been there done that -the black smoke like crazy. One of the first things i checked.

Heres a pic of my fuel prime rig.  Can i tape (teflon

tape) the brass to brass fittings?


Look right?  Valve installed on top entry of primary filter

-dave

[Dlsnow]

Wooooo down the road i went.

Pouring rain here in central Wicsonsin today...of course
Filled and replaced the primary fikter.
Setup that pictured prime rig to the top inlet of the primary filter
Discovered and used yellow diesel appropriate pipe fitting tape. Stayed away from the last few threads.
Ran prime rig for 2 minutes or so
started right up

PO said he hasnt had thia issue before.  And that the genset is pipped directly to tank...not tee'd

Ill probably cleanup the install and leave it permanent.  Just in case.

Thanks to all you guys/gals?
Victory video below
 https://www.youtube.com/watch?v=FINRdFSnFTI&feature=youtube_gdata_player

[luvrbus]

He caught that goose Gus and didn't have to chase it far, like others said if they have air and fuel they run maybe not perfect but they will run,glad it worked out for you some DD can be a PITA to prime

good luck

[gus]

Good news, nothing like the sweet sound of a purring DD!

A few things still puzzle me; you said nothing about the secondary filter - was it full also? If so it is a mystery to me why it wouldn't start? I never did understand why you worked on the primary filter only?

The goose may not be caught yet because I read nothing about what caused the loss of prime. If the cause isn't known what is to keep it from happening again? Could there be a leak between the primary and pump suction side which will pull air in. A leak after the pump will show raw diesel but an air leak before will show nothing.

When priming through the primary filter does this also fill the secondary? If so, where does the air in the secondary go? Will using your primer pump at the secondary work just as well - better? I plan to install a prime connection but had planned to connect it at the secondary. Am I better off to do it at the primary?

When I lost prime on the 4104 it was the check valve at the primary filter which caused the primary to empty. It was a while ago so I don't remember if the secondary emptied also but I think it didn't.

Thread tape makes me nervous. I use teflon paste in a tube on all thread connections so I don't have to worry about those sneaky little slivers of tape getting into any system.

[Dlsnow]

 Sorry if i didnt mention the secondary.  It spun off and was full.  Primary was so difficult to remove...it was an event. 

So both filters were full.

According to my interpretation of the pic below the trapped air would end up in the tank after chasing it with fuel through the diagram.  Installing the pump at the primary fikter (fuel strainer as diagramed) seemed to be an effectve location.


Saw mixed reviews of both paste and tape.  So i flipped a coin.

As to the "goose" still havent caught it.  Not sure why it lost prime.  PO confirmed that hadbt happened to him.  He had the bus from 1991 to 2011.  Have nt had the same issue yet.  Getting it to the mechanic next week.

[gus]

Thanks. I'm convinced, I'll put mine on the primary also.

Now that I think more about my last post, if there was a leak from the primary to the fuel pump it would have shown up when you pressurized it with the primer pump.

Just a thought but seems to me there was a string here a while ago that said a leaking return line would empty the return line and cause a loss of prime. Not sure I really understand that but it may be something for you to research.

Maybe an emptying return line empties the injector lines?? Seems to me that happened on my Dodge Cummins PU but not sure now which line was leaking since it was a long time ago.

The good thing about paste is there will never any of those nasty little shreds. However, I can see that using way too much paste could cause problems, but that seems to be a common sense thing.

[DMoedave]

Last December i changed my fuel filters before heading south to Arcadia. I lost prime at the house and refilled and fired her up. Got off the island and headed into NJ and about 80 miles from the house, i turned off 80 onto 287 south and i felt her lose power momentarily and as i came around the ramp she died and i pulled over into the most perfect spot, off the road in a median of sorts. I reprimed the filters and she ran and shut off. did this about 4 times and it was cold and losing daylight. I have no idea what finally made her run but never a problem that day and the next, all the way to fla to my sisters in Ocala. Next morning she had lost prime, and the same thing happened pulling into Arcadia. I would reprime and it seemed fine for awhile but at Arcadia it got worse. I think it was shut off valve installed to make changing the filters easier. It was leaking or sucking air at the handle packing. This stuff will drive you NUTS lol. Have fun with your bus

[Dlsnow]

I have put about 600 miles on over the last few days overnights and a good number of stops.  Hasnt lost prime again. 

I installed the shutoff valve so that the handle faces down when closed...hoping gravity will help keep it closed.  Probably going to add sone kind of safety to hold it closed.  Dont want fuel dumping while driving.

Thanks again for all of the help from everyone.

[gus]

A very small air leak won't show up with daily driving, it usually shows up after sitting awhile.

Don't understand how a shutoff valve could make changing filters easier??

[luvrbus]

Gus some buses like MCI have the filters lower than the tank they just keep siphoning when you remove the filter so people install a valve to stop the flow

[gus]

Thanks, I learn something new every day on this board!!