MCI wont start

[viking1]

    I got a 1989 MCI 102C3. I had not ran it for about a month. Yesterday I started it and it started normal. After it ran for approx. 5 - 10 minutes it shut itself off. When I tried to restart it, it would only crank and not fire. Sounded like it tried a couple of times with no success. I pulled both fuel filters and found them to be 1/4 full or lees with fuel. I filled them with diesel and put them back on. No change. Any Ideas. Im wondering if I might have a bad fuel pump.

[gumpy]

Sounds like your fuel tank is empty.  The empty filters is a sign of this. However, it's possible that you have an air leak in the fuel line which has allowed the
fuel to drain back to the tank and suck air into the line. In this case, the engine would start and run on what was in the filters and pump, but when the air
 got to the pump, it would airlock and die. The pump
is not self priming.

It's probably not the pump, or it would not have started in the first place.

You will need to reprime the fuel system and remove all the air between the tank and the fuel pump. Suggest you search the archives on how to do this. The
electric pump is the best way, though not necessarily the cheapest way.

[viking1]

Thank you for that. The fuel tank is approx 1/4 to 1/2 full so I dont think im out of fuel. How do I track down an air leak in the fuel system.

[bobofthenorth]

Probably the simplest way is to buy yourself a 12 volt inline fuel pump and plumb in it at the tank.  It will solve your priming problem and keep the engine running while you track down your air leak which will turn into a fuel leak when you put the pump in.  Pressure wash everything until it looks nice and then use the bus for a while - the leak will be the place that gets dirty first.

This comes up regularly so the search function should turn up lots of threads for you - this one came up near the top of my search:
http://www.busconversions.com/bbs/index.php?topic=18135.0

[chev49]

course in my case is paper in the check valve

[Jriddle]

I had to ask this board this very same question. Check to make sure your engine shut off switch in the back is on. If it is off you will be able to start engine until air pressure builds and then the shut off will shut you down. I am not sure this is you buses problem but it sound like my situation.

John

[viking1]

interesting, I did notice that the air pressure was around 60psi when it shut down. Where is the shut off valve and how do u move it manually

[Jriddle]

Mine is in the back as you face the engine on the left side.

John

[luvrbus]

His is probably a DDEC 6v92 or 8v92 his problem is it lost prime the pump is good or the filters would not be low

[viking1]

Thanks, Its a 8V92. Not sure if it has a DDEC but im guessing it does. I will try again tomorrow

[viking1]

how would it have lost prime. It was running for a good 5 to 10 minutes before it died. After it died I was unable to restart it.

[belfert]

You may have a cracked fuel hose allowing air into the system.  That would cause a loss of prime in some cases.

[Van]

Or... you could have a collapsed fuel line, in which case not enough fuel as was in my case.

[blank]

how would it have lost prime. It was running for a good 5 to 10 minutes before it died. After it died I was unable to restart it.

  I dont believe there is enough fuel in the filters to run it that long without any fuel flow, but regardless, its lost prime. Could be a loose fitting, even a loose filter, anywhere it can suck air rather than fuel will cause the problem, and running time depends on quantity of air to fuel. IOW, it was pulling air in with the fuel which allowed it to run longer than it would have without any fuel flow.

  Is there some work youve done previously, fuel filters? Lines? tank? Anything with the fuel system you have taken apart and put back together? The filters need to tight like an oil filter, 3/4 turn after contact. They do not need to be tightened past that point

[Busted Knuckle]

Lost prime is going to be the problem.
Reason? Could be many reasons such as the cracked line, hole in a line or whatever. Usually (not always) it's a worn out, or comprimised check valve that allows fuel to back flow when it's not supposed too!

course in my case is paper in the check valve

As chv49 mentioned in his case it was paper in the check valve.

Now one would ask how would paper get in there? Hmm what is inside a fuel filter? Paper! So my guess would be old or defective fuel filter!

AT any rate viking1 if it were me I'd REPLACE the filters with new full filters and either add a primer pump or use an old school solution and supply fuel & pressure to the engine long enough to get it up and running on it's own!

And yes an engine can run on the fuel in the pump and filters about 5 mins before running out if it's lost prime!
  BK