Fuel on the ground under engine!!??

Devin & Amy · December 09, 2006, 02:34:03 PM

Hi all,
I have what looks like a fuel leak under the pass. side fuel filter area under engine area.
The area on the ground is about 2'x4'.
It got down to 17 last night here in Alabama, but my wife had the bus plugged in. It's definetly diesel fuel.
Where do you think it's coming from? I can't find any drips, and the diesel has spread so far it's difficult to tell the exact drippoint. It looks as if it is coming out of the right side slobber tube.

I haven't started the bus yet, in case I ruptured something. wouldn't it then suck air?

I need ideas of where to look, or a test to try.

Thanks,
Devin

niles500 · December 09, 2006, 02:58:02 PM

Check to see if you didn't crack your filter(probably at the bottom) - that would explain the one-time discharge - HTH

larryh · December 09, 2006, 03:30:15 PM

I doubt if it's coming out of slobber tube get some cardboard ans slip under it for a bit and check for drips and where it's coming from.

LarryH

Kwajdiver · December 09, 2006, 03:39:22 PM

Devin,

Where in Alabama are you? I'm currently in Mobile.

Bill Williamson
MCI-9

Devin & Amy · December 09, 2006, 03:46:46 PM

Bill,
We're in Demopolis. We stay at a place called Foscue Creek Park(Corps Park).

Cell (479)970-8337

Devin

Melbo · December 09, 2006, 05:28:55 PM

I had a leak at a similar location on my 8

It turned out to be the fuel sensor that was leaking it had a cracked plastic body

It had been bypassed so it served no function

I just removed it and plugged the hole

Just a thought from my experience

Melbo

gumpy · December 09, 2006, 05:52:04 PM

Put a piece of cardboard under it. Run the engine a bit to make sure all the fuel lines are full. Then watch for drips.

Devin & Amy · December 10, 2006, 02:25:28 PM

Found it. It's a fuel sending unit, but what for?
Can't find my D**N book, so I don't know how I should proceed.
Still haven't fired it up. would rather fix it first. will take it off tonight and take it with me to town tomorrow.
Devin

FloridaCliff · December 10, 2006, 03:06:04 PM

Devin,

Probably the fuel pressure sensor.

Is it on the secondary filter?

Mine was leaking also and had to replace.

Little trick, if it should fail, sender part, just ground out to keep going.

Get yourself a little 1/4 plug(if I remember right) at the hardware, quick fix in a pinch.

Kind of a funny sensor as you will know rather quickly if you lose pressure, of course could save a reprime.

Cliff

Stan · December 10, 2006, 05:59:59 PM

The fuel pressure sensor on a MCI is part of the starter interlock system. When the fuel pressure switch is activated, you cannot engage the starter solenoid.. It is a normal;ly closed switch to ground so Floridacracker is correct about putting the sensor wire to ground. This will allow the starter to work but you will not have the safety interlock.

gumpy · December 10, 2006, 07:14:49 PM

Devin,

I sent you a message regarding this.

Stan is correct. This is part of the safety shutdown system. If your shutdown system is activated due to low oil, high temp, or low water, you can override it by holding down the start button to get the bus off the road. This pressure sensor disconnects the starter solenoid ground once fuel pressure is detected, so the starter won't continue to spin while holding the button in.

It'll need to be replaced, but you can remove it for the time being and plug the hole.

And, as Cliff says, if the switch fails, you can ground the output and start the bus. I keep an alligator clip next to mine. Have had a lot of problems with this switch. I'm on the third one. So far, it's working better than the last two. One leaked. One failed. This one's still working ok.

craig

NJT5047 · December 10, 2006, 08:08:40 PM

Quote from: gumpy on December 10, 2006, 07:14:49 PM
you can override it by holding down the start button to get the bus off the road. This pressure sensor disconnects the starter solenoid ground once fuel pressure is detected, so the starter won't continue to spin while holding the button in.
craig

Mine leaked too. Never been functional since I bought the bus. It was jumped. I removed it when it started leaking. One thing regarding this switch that I wish to run by ya'll...do you have to hold the starter button down when the "override" switch is held on?
Does this apply to DDECs? I was under the impression (however mistaken it may be) that the override switch would keep the bus running for several minutes as long as it was held in the on position. Is wrong? May be that the shutdown system on an MUI operates differently?
JR

gumpy · December 11, 2006, 05:00:56 AM

I'm not familiar with the NJT configuration, or DDEC, so I can't comment on either.

On a standard, non-DDEC, non-NJT configuration, the starter button on the dash is the override switch. If the safety system is engaged due to one of the sensors, you can hold the button in, and the engine will start and continue to run while button is held. The pressure switch is there to disconnect the starter so it won't keep spinning while the engine is running and the button is being held. Without it, the starter will continue to spin while the button is held and could result in severe damage to the starter and possibly the flywheel.

One other point, if your safety shutdown system is functional, you typically have to hold the button in upon startup until the low oil light goes out on the dash. If you don't hold it, the safety system will cause the engine to shutdown. This pressure switch is needed here, also, as the engine is running during that extra few seconds of hold time.

It's not unusual for the safety shutdown system to have been disabled, though. You should test it to make sure it is functional.

craig

JackConrad · December 11, 2006, 05:08:56 AM

That switch was leaking diesel when we bought our bus. I went to a local truck parts store and bought a replacement switch. It failed electrically in a few months. I then ordered a replacement switch From Luke. This switch was much larger than the first replacement. 6 years later it is still working. Jack

Stan · December 11, 2006, 05:52:45 AM

Bit of trivia: Prior to the late MC-7s, MCI had a switch marked 'Overrule' which was an option on bus purchase. This switch overrode the safety shutdown circuit and let the bus be started and moved to the side of the road. With an overheat shutdown you could run the bus at high idle to get the temperature down more quickly. If the switch was not ordered with the bus you had no way to restart a hot engine without removing the wire from the shutdown sensor. This system was replaced by the fuel pressure switch interlock on later models with MUI engines.

I have no idea what sytem they use on DDEC engines. NJT5047 mentions an 'Override' switch which may duplicate the old 'Overrule' switch by fooling the computer.