hey all,
this weekend when working on the bus I found I have a fuel leak and I do not know what the part is or what it is for.
if you can help me figure out what it is and also where I can get a replacement I would really appreciate it.
in the below picture it is the black plastic cap with 2 wires on top of it.. it is leaking at bottom of cap where cap attaches to the metal part.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwww.impaks.com%2Fimages%2Fken%2Fbus%2Fimg-20111002-00045.jpg&hash=1148e90a5cdd173214a402f6e7e35c3e5e1e799c)
thanks in advance
Ken C
Looks like a pressure switch to me.
;D BK ;D
any idea where best place to get this part?
When I first got my MCI with a Detriot Diesel it too had a fuel pressure switch. I believe some fleet operators ordered their buses with this option - something like preventing drivers from cranking and cranking on an engine that has lost prime, burning out the starter, etc. If I recall correctly it needs to detect a few lbs of fuel pressure to allow the starter to engage.
Like yours, mine leaked, and eventually it wouldn't let the starter engage, left me high and dry in a remote campground. It had leaked enough fuel to cause me to lose prime - a real no-no.
Part of the long term solution was to remove the pressure switch since we are our bus's only drivers, send fuel directly to the secondary filter, and ground the wires to 'trick' the system.
I can't tell you how to do these things, but I might mention that there will be a gathering of bus nuts, including some real pros, at Palmetto Cove Campground near Spartanburg SC this coming weekend. Any of several folks there would be happy to advise you. See the post elsewhere on this board regarding the 'Non-Rally', hosted by Kyle Brandt. Not too far from you there in Raleigh. A free rally except for $22 per night camping.
Good luck!
Mike in GA
Mine left us sitting in a reststop in Ohio one night, after we figured out what it did I just removed it and put a plug in the fitting and hooked the wire's together. From what I understand they are known for problems, so I eliminated one problem. Jason
The fuel pressure switch is intended to prevent the starter from engaging on a running engine.
It is critical to the proper functioning of the auto-shut down bypass, if the coach is so equipped.
Holding in the starter button is how you keep the engine running if the auto-shut down has engaged... starter won't cut out without the fuel pressure switch... oh dear...
as long as you know the rest of the story, do to your own coach what you want.
happy coaching!
buswarrior
Quote from: Mike in GA on October 04, 2011, 03:19:56 PM
When I first got my MCI with a Detriot Diesel it too had a fuel pressure switch. I believe some fleet operators ordered their buses with this option - something like preventing drivers from cranking and cranking on an engine that has lost prime, burning out the starter, etc. If I recall correctly it needs to detect a few lbs of fuel pressure to allow the starter to engage.
Like yours, mine leaked, and eventually it wouldn't let the starter engage, left me high and dry in a remote campground. It had leaked enough fuel to cause me to lose prime - a real no-no.
Part of the long term solution was to remove the pressure switch since we are our bus's only drivers, send fuel directly to the secondary filter, and ground the wires to 'trick' the system.
I can't tell you how to do these things, but I might mention that there will be a gathering of bus nuts, including some real pros, at Palmetto Cove Campground near Spartanburg SC this coming weekend. Any of several folks there would be happy to advise you. See the post elsewhere on this board regarding the 'Non-Rally', hosted by Kyle Brandt. Not too far from you there in Raleigh. A free rally except for $22 per night camping.
Good luck!
Mike in GA
thanks for info.. as for this weekend I am heading with family to troy , nc for a family and friends camping weekend
Quote from: buswarrior on October 04, 2011, 07:09:39 PM
The fuel pressure switch is intended to prevent the starter from engaging on a running engine.
It is critical to the proper functioning of the auto-shut down bypass, if the coach is so equipped.
Holding in the starter button is how you keep the engine running if the auto-shut down has engaged... starter won't cut out without the fuel pressure switch... oh dear...
as long as you know the rest of the story, do to your own coach what you want.
happy coaching!
buswarrior
I will start with I do not know what the auto shut down bypas is.. so I am guessing mine doe snot have that :) but I could be wrong..
is it a switch or something ?
so if I do not have that option then really would not be a huge deal, correct?
The fuel pressure switch prevents the starter from engaging when there is fuel pressure.
In other words, when the engine is running.
Without the fuel pressure switch, the starter will try to engage if you push the button with the engine running, with whatever resulting chewing of teeth that takes place.
Choice is yours as to the risk of whether you, or someone else, will accidentally push the starter button with the engine running.
Small parts like this get ignored by the last commercial operator of the coach, so many busnuts over report having to fix it. Once you put in a new one, it will be a long time before you have to think about it again.
Auto shut down has no visible clues in driver's area. It was optional from the factory on the older mechanical coaches. If the engine is equipped, and is stopped by the auto shut down, due to over temp or low oil pressure, it is usually not in a good location, so the bypass for the system is built into the starter circuit, hold the start button in continuously, and the engine will run until you let go the button so you can move to the shoulder, out of the intersection, etc.
Check the rear electric junction box for the presence/connection of an engine stop relay.
The busnut community is split on whether we like and keep, or disconnect and discard the auto shut down system.
With the newer electronic engines, there's no choice to make, as it is part of the computer, and there will be a separate bypass switch on the instrument panel somewhere.
happy coaching!
buswarrior
Bruiser,
Most likely your bus has the option!
Almost all MCI's and some SOB's (some other brand) have/had it.
The leaking pressure switch even still being there is what tells me yours still has it.
What it is for is say the engine runs hot and the auto shut down starts flashing and beeping that it is fixing to shut down the engine.
But you are in an unsafe spot to stop. (let's use a 5 mile long bridge for example)
Then the driver can push and hold the start button down, while he continues to drive on across the bridge to safety and find a place to park off the road.
Now think about it for a min. if you push the start button isn't the starter going to engage?
NO, not if this pressure switch is still in place and still properly hooked up.
Many disable or toss them, it's totally your choice!
Personally I like the way Setra & some SOB's do it with another switch than the starter button!
;D BK ;D
Opps I see BW was quicker than I was! ;)
;D BK ;D
Quote from: Busted Knuckle on October 05, 2011, 06:56:16 AM
Personally I like the way Setra & some SOB's do it with another switch than the starter button!
;D BK ;D
Yup, like ours. A separate override switch that even has a little cover on it ;D. MCI just caught up with those Setras a little later on in the game ;)
ok well I guess it is off to the parts store to see if they can get me a new pressure switch to replace this one..
thanks for all the answers everyone..
That switch is an 8 to 10 psi switch, normally closed at 0 psi, opens at 8 psi, and it is the ground path connection between the starter relay coil and ground. Note - the starter relay, which is a cube relay in the rear electrical panel, and not the starter solenoid, which is on the starter motor and which is itself controlled by the starter relay. So you need a two terminal switch, that is normally closed and which opens around 8 - 10 PSI. The reason it has to be a two terminal switch is that the more common single terminal switches depend on a good ground through the pipe thread connection, and presumably the designers didn't think there would be a dependable ground connection through the various bolted bits of the fuel filter head.
Brian