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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: BlueScarecrow on November 15, 2015, 09:29:06 AM

Title: More 8V71 Woes
Post by: BlueScarecrow on November 15, 2015, 09:29:06 AM
Bus started and died. This is uncommon because it has never let me down so far in the past 5 years... it has always jumped to life instantly, even after 6 months of sitting. Installed new strainer... installed a new filter (yes I filled them to capacity before installing)... bled the line and used starting fluid to get it going. It came back to life, but then died after 3 minutes of running. Don't know enough about diesels to figure out what's wrong. NEED HELP! Thanks!!!
Title: Re: More 8V71 Woes
Post by: eagle19952 on November 15, 2015, 10:05:24 AM
there is only one thing it can be...a fuel problem.

what where and how are the questions.

sorry,  that's all i got.

except perhaps a bucket a pump and a hose.

good luck. ;D
Title: Re: More 8V71 Woes
Post by: bigred on November 15, 2015, 11:43:00 AM
Check the shutdown solenoid!!
Title: Re: More 8V71 Woes
Post by: goldgiter on November 15, 2015, 12:35:33 PM
Not being a smart a$$ but do you have fuel in the tank?

Wes
Title: Re: More 8V71 Woes
Post by: luvrbus on November 15, 2015, 12:48:56 PM
If you started it from the rear without the front switch on it will die when the air pressure builds up.If that is not the cause prime the system good this time when it fire give about 1/2 throttle when the gear pumps get wear they won't pickup at idle 
Title: Re: More 8V71 Woes
Post by: BlueScarecrow on November 15, 2015, 12:57:17 PM
Not enough air for the solenoid to work. I've tried turning off the ignition after a couple of minutes of running and it wouldn't work. I had to go back and do it manually.

It doesn't shut down suddenly... it runs down like it's running out of fuel. Fuel in the tank registers as a little over a quarter tank. Very strange.

Maybe the fuel pump is going out. Has anyone ever installed an electric fuel pump at the tank to push the fuel to the back? In case one ran out of fuel.

It won't crank from the back without the front switch in the on position.

Tried the 50% throttle... but it just won't catch. Surprised that no one has ever come up with a bleeder button at the back.

Thanks for all the replies!!!!!
Title: Re: More 8V71 Woes
Post by: luvrbus on November 15, 2015, 01:06:55 PM
MCI's are usually easy because the filter is so low on the engine frame does your have a valve before the filter ? I for got 1 time and left the valve closed. They bleed through the return line there is no need for a button
Title: Re: More 8V71 Woes
Post by: Scott Crosby on November 15, 2015, 01:35:25 PM
I'm have run out of fuel at 1/4 or more of a tank several times... My pick up tube and the angle the bus is at will let it suck air, keeping it above half tank is best for me.
Title: Re: More 8V71 Woes
Post by: BlueScarecrow on November 15, 2015, 03:16:09 PM
The shut-off is above the strainer/Filter combo holder; don't think I forgot to turn it on, but I'll look. This bus was manufactured in 1983 an all these lines and fittings look like they are 32 years old too. Maybe it's time to replace the lines and fittings.

Thanks all!!!!!
Title: Re: More 8V71 Woes
Post by: Fredward on November 15, 2015, 03:33:30 PM
Speaking from experience. Don't trust the gauge. Those sending units get rusty and sometimes stick. I'd stick the tank to be sure you have fuel. You mentioned an electric fuel pump; I have one permanently installed in a bypass circuit ahead of the filters that I use after changing fuel filters. (And the ONE time I ran out of fuel).

Seriously, I ran out of fuel 3/4 of a mile from home on the gravel road. Had a neighbor come pull me home with a tractor. Turns out the gauge doesn't exactly go all the way down to "E".

Fred
Title: Re: More 8V71 Woes
Post by: OneLapper on November 15, 2015, 03:35:11 PM
My bus did the same thing a couple of weekends ago.  Somehow the Jake switch was on Low.  It took about a minute for it to slowly die.  Thankfully I figured it out without much drama..... I think this is the third or fourth time I've had that happen.
Title: Re: More 8V71 Woes
Post by: zimmysurprise on November 16, 2015, 12:14:45 AM
I'm not sure if your MCI has an air shut down or not, but I had a similar problem once when the solenoid was stuck. I thought it was running out of fuel, but watched the solenoid shut down slowly as the bus built up air. After it shuts down, are the fuel filters still full?
Title: Re: More 8V71 Woes
Post by: ol713 on November 16, 2015, 09:51:30 AM

     Hi;
       In addition to what everyone else mentioned, have a look
       at the fuel pressure shutdown switch.  Check the ground
       wire comming from that switch.  The wire could be broken
       or almost broken.  It is located approx 6" from your shut
       off valve near the first filter.
                                        Good luck,   Merle
Title: Re: More 8V71 Woes
Post by: BlueScarecrow on November 16, 2015, 02:53:22 PM
I would like to put an electric fuel pump by the tank. Any make or model I should look for?. The fuel pressure switch has a broken wire. The ground is ok. I thought that switch disabled the starter after the engine is running. Does it also affect the fuel delivery?

Thanks!!!!!
Title: Re: More 8V71 Woes
Post by: Fredward on November 16, 2015, 03:27:53 PM
I'd put it by the filters. Lots easier to plumb in there. I bought a 24volt inline pump at Napa. I plumbed in a bypass circuit that only gets activated when I need the pump.
Text me if you want pictures of my install. 612-801-4826.
Fred
Title: Re:
Post by: daddyoften on November 16, 2015, 06:19:51 PM
Electric pumps are better pushers than suckers. They may work ok way down by the filters but would perform much better nearer the tank
FWIW
Eric


Sent from my XT1254 using Tapatalk
Title: Re: More 8V71 Woes
Post by: blue_goose on November 17, 2015, 02:02:37 AM
My coach has an electric fuel pump at the tank installed by MCI.  They are not made to pull fuel.
Jack
Title: Re: More 8V71 Woes
Post by: luvrbus on November 17, 2015, 02:17:31 AM
Buy a Airtex flow through inline electric pump rated for diesel,you are only priming not running the engine from it.You can mount it at the filters or anywhere in line without any ill affects on your fuel system and it works 

good luck
Title: Re: More 8V71 Woes
Post by: ol713 on November 17, 2015, 05:17:21 AM
Quote from: BlueScarecrow on November 16, 2015, 02:53:22 PM
I would like to put an electric fuel pump by the tank. Any make or model I should look for?. The fuel pressure switch has a broken wire. The ground is ok. I thought that switch disabled the starter after the engine is running. Does it also affect the fuel delivery?

Thanks!!!!!

           YES  ---   I believe so.    Maybe someone else can verify this.
                                            Merle
Title: Re: More 8V71 Woes
Post by: luvrbus on November 17, 2015, 06:50:36 AM
Yep the fuel switch is there to just disable the starter,there is a switch to over ride the fuel switch if needed in a emergency and his starter is engaging so it's not the fuel switch   
Title: Re: More 8V71 Woes
Post by: bevans6 on November 18, 2015, 08:38:14 AM
The fuel pressure switch has absolutely no effect on fuel delivery.  It is a normally closed switch that opens when it senses around 15 psi of fuel pressure.  It's actually a good way to tell if you have prime, if you felt like hooking a test light to it or something.  What it does is provide the ground connection for the starter solenoid.  If there is no fuel pressure the starter solenoid has a ground connection and the starter can turn on.  If there is fuel pressure, the ground connection is open and the starter cannot operate.  Top Tip - if you have an Airtex fuel pump to prime with (like I do, thanks again Clifford if I didn't already credit you with giving me the idea) the Airtex pump can generate enough fuel pressure to trip that switch open and you get a no-start.  Happened to me, took about 3 minutes for me to disable and bypass that switch after spending some indeterminate amount of time figuring it out...   Oh the lost hours spent searching for the latterly obvious....   ;)

Brian
Title: Re: More 8V71 Woes
Post by: robertglines1 on November 18, 2015, 11:22:02 AM
on the 78 mci 8 v 71 had the transfer pump go out. Mounted on front of engine( opening rear doors is rite there). pull line going to injectors/head and see if fuel is coming out of it. when cranking.  FWIW   would pick up out of a 5 gal can on ground but wouldn't draw from tank. Was weak.   changed it and all was good.