I received an over overwhelming response to my posting on the
Bulletin Boards and Email group concerning this topic. Seems there are two scenarios on
this for everyone. Those who have run out of fuel and had to deal with recharging their
engines and those who have yet to enjoy the experience.
ask -"How can anyone run out of fuel when you have the capacity to carry well over a
hundred gallons? What a dumb thing to do." There are several reasons this may happen.
First, not all buses are equipped with fuel gauges. Some may only have a low fuel light
and it may be broke. Without an accurate way to tell what's in the tank its only a matter
of time before you maybe caught miles from the next "Diesel" fuel station. The
coach may have been sitting for along time and lost its prime. The one way valve that is
suppose to keep this from happening maybe bad. Leaks in the fuel system could cause air to
enter and stop the flow. I have had more than one professional diesel technician tell me
that they have been on many service calls for this easy to correct problem.
Well, wanting to be prepared - I bought the one way valve that
several folks recommended from the Detroit dealer. At you can see, its gold colored and
has a price to match.
Next, I needed a pump. The AC
Delco In-line Fuel Pump, Part# EP154 was chosen because it was 24v. This made it very
convenient to connect to the unused original wire for the toilet blower. The remainder of
the parts were brass fitting, tubing and Teflon tape.
The CAD drawing below shows the layout and should
be adjusted to fit your installation. This was installed in an MC8.
Now after having completed this project, the
biggest pain was getting all the parts together. If are installing this on an MC8, the
Parts List will work. For other installations, just change the fittings to suit. The pump
comes with a nice bracket that lined up perfectly with a hole left from the toilet tank
Break the fuel line at the connection block in the forward
engine compartment and install all the fitting and one way valve. You will want to use
Teflon tape on all connections. Bend the 3/8" tubing to match the opening at the tee
and pump outlet. Slide the flare nut over the tubing and flare the ends.
Important! - If your coach has a pressure switch on the fuel
filter that provides a ground for the starter relay, you need to provide a ground while
the pump is on or your starter will not work! The pressure switch cuts out the starter
after fuel pressure is sensed at the secondary fuel filter. Because the pump is located
upstream of the filters and this switch, you will get prime, but no starter. This is a
safety feature to prevent the starter from engaging after the engine is running.
Craig posted on MAK BBS - "I heard of a case where the
starter stuck (relay or solenoid), and continued to spin after the engine started,
overheated, and burned up the bus. Second-hand, can't confirm this, but sure would hate
for that to happen to me. At the very least, you could do some serious damage to the
starter and/or engine"
Connected the electrical by crimping an eyelet to the ground
wire and putting it under the pump hold down bolt. Route the positive side to a double
poll, double throw switch (DPDT), wire one side to the switch to activate the pump and on
the other side route the starter relay ground through the switch to provide a ground.
After the engine starts and is running on its own, turn the prime pump off, this
deactivates power to the pump and reconnects the circuit to the pressure switch. The
switch can be installed in the remote start box.
Here is a photo of the system installed.
The system worked great! What I like about this setup is - it
installs neatly up against the ceiling in the engine compartment, even using an existing
mounting hole and wire. The one way valve, though more expensive than using a ball valve,
makes the system automatic and with fewer parts. Please let me know if you have any
comments or suggestions.
The following was submitted byCharlie (82MCI9).....Titusville Fla.
Thanks for the article, it helped greatly. I took the bus for a oil, filter, grease job. 3
weeks later, it wouldnt start. It was hard starting, sputtering and finally died. A diesel
mechanic said that sometimes, 6V92TA and other DD engines, will bleed down in the
injectors. This causes air to get into the fuel system. I suspect that is what happened. I
installed the fuel pump, right on primary fuel filter. Came out beautiful....( see
photo)...in 3-4 minutes, the engine started, like it always did.....first shot. I went
with ball valves, instead of check valves. Lots cheaper. Thanks again, Charlie
The following was submitted by Marc Bourget:
Just reviewed your excellent article on the fuel primer pump installation. The picture and
drawing are just great. One thing, the tube out of the pump and back into the line appears
to be copper. Is this correct? If so, my past experience makes me fear (perhaps
unreasonably) that unsupported copper over this length may flex enough to work harden and
eventually crack. The fact that this deals with the fuel system makes me very cautious.
What are your thoughts about supporting the copper between the pump and reattachment to
the fuel system?
Thanks for your thoughts
>You bring up a good point. I when back and looked at
the system again and even though all the parts are supported very well by the metal strap
holding the >pump, another clamp around the 3/8" tubing and fasten to the coach
would be very easy to add.
>I am posting your suggestion with the article and will add the modification to my
>Tom Hall MC8
>Coach Conversion Central Online
This is what the service manual recommends:
Detroit Diesel V-71 Manual Reference
Section 13.1, Page 2
"To ensure prompt starting and even running, the fuel system must be purged of air
and full of fuel from the supply tank to the restricted fitting at the fuel return line.
To accomplish this, a manual priming pump, such as J 5956 or an electrical type priming
pump can be adapted easily to the fittings provided on the primary or secondary filters.
To be sure the injectors are lubricated and in order to have less resistance to priming
flow cause by the static fuel pump, priming through the secondary filter is preferred. The
system should be primed until no air is present in the fuel flow from the return line.
Pressure should not exceed 15 PSI for ease of handling and safety reasons.
Pressurization of the fuel tank, although not recommended, can be used with controlled air
pressure and a modified filler cap (do not exceed 15 PSI). If this system is used, be sure
the return line from the head is disconnected to bleed the system, or no flow will occur.
Reverse flow through the return line should be avoided to prevent reverse flushing of
filters and flushing residue from the fuel back into the injectors. Special provisions may
have to be made on dual tanks to prevent loss of pressure from the vent on the tank
opposite the tank being pressurized."
Detroit Diesel Corporation
I would like to thank everyone who gave me input on
this. From your emails there are many ways to accomplish this. Here are some additional
EddieB Bradley - Pekin, Illinois -
72 Eagle 05 - I mounted a "small" auxiliary fuel pump
(automotive type, purchased from "AutoZone") in a "Td" fuel line
bypass, controlled by two ball valves. One ball valve, mounted AFTER the "T" leg
in the main fuel supply line (let the "through" leg go on to the primary fuel
filter), allows tank fuel to also flow to the auxiliary pump, allowing the pump to
function as "auxiliary" or "assist" to the main, in case of diminished
capability or slow failure in the main pump. The other valve (mounted AFTER the
"through" leg of the "T" mentioned above), shuts off direct tank fuel
flow to the filters and main pump completely, allowing the auxiliary to create a vacuum on
the tank line, and suck up fuel all the way from the tank.
Terrence J McGraw - Have "MACK" hand pump on the return fuel line,
it will prime the rack, is in line all the time, also have an electric oil pressure gauge,
(JC Whitney) in a spare port on the rack, 6-71 needs around 70 pounds pressure, gauge
shows that, readings get lower as filters get clogged
Dave Galey - Break your fuel line from
your tank to your primary filter. Add an electric fuel pump in parallel. Between the tee
to the inlet side of the pump and the tee from the outlet side of the pump. Install a
Detroit Check Valve (kinda priceyabout $50) This way when the electric pump sucks
from the tank it closes the check valve and pumps fuel into the primary filter and will
charge your system. When the pump is off, fuel flows directly to the filter. I have
changed filters dry and charged them and my system this way. Some guys have used a
manual wobble pump What ever works!
So now, if I run out of fuel, all I have to do is get more fuel into my tanks, turn two
ball valves, flip a 12 volt pump power switch, and let er run for a minute or two.
She sucks up the fuel from the tank, floods the filters, the heads and injectors, and
returns the balance of the fuel on the return line. Works great! It keeps your hands and
clothes clean too!.
Same deal for changing fuel filters. I can even prime the filters without having to
pour fuel into them while holding them in my hands. Just make sure to open the air vent
fitting on the secondary filter if you want to make the filters fill faster.
I may take a picture of the set-up and e-mail it out if you would care to get one
(whenever I get a chance to shoot it).
FAST FRED - I found that the time and trouble of installing a
check valve and electric pump for something that should never happen was too much to
contemplate. So in my big tool box is a little $50 dollar toy from the old days, when I
used to fix vacuum doors and, bleed hydraulic brakes on my car.
Its a Mity Vac, Summit has them. A metal hand pump with universal fittings,hoses,
and a gage.
When the fuel pump on my 4106 died over the winter it was a snap to suck fuel to the
filters thru whatever valves there are. Filled up the changed filters and - VAROOM! But
the damn thing would only run for a minuet. Suction applied to the fuel pump from the
filters revealed an air leak, so when I pressurized the line looking for a leak fuel
poured out the fuel pump. Problem solved, after I put in a new fuel pump. As sucking on
fuel lines for information is part of Bussin, IM happy to have a simple trouble
shooter in a little box of its own.
Want to know when any tube or pipe has a leak? Suck it to 28 in vac and watch, then
pump it up with diesel or ATF that leaks real easily, and continue to watch!
Its fairly easy to trouble shoot things with hose,tubing or pipe. Just one lazy guys
other way of solving the common problems.
George Myers - I got mine a one way valve at the salvage yard
for free. They told me Detroit's do not have such a thing. When I found one, they had no
set price and gave it to me. This is a first for me. My 6V92 has one that could be moved.
Both valves have a cylindrical center section, about an inch long and an inch in diameter.
There is a hex nut on both ends that is an inch across and an 1/8 inch thick. Beyond the
nut are the pipe thread fittings. Mine screws into the top of the casting for the first
The one from salvage was full of crud. I opened it and cleaned it easily. It is something
to check occasionally.
I just thought of another idea. My diesel power plant has an electric fuel pump. One
could put a Tee and a valve, or a two way valve, after the pump and run a line to a Tee at
the engine after the check valve. Fore safety, another valve there would be a good idea to
ensure fuel is not lost if something goes wrong in the line.
If the tank is empty and it does not run, you are out of fuel. Another good idea is to
have a fuel pressure gauge after the second filter. If it does not read what it normally
does, something is wrong.
Les Harold - Ohio - You will have to modify the fittings but
you can check a Ford truck pump on the frame rail. They use two, one in the tank and one
on the frame rail. Just a thought. And if you dont want electric, a lot of
construction equipment uses a little hand pump that is left in line all the time and you
dont need the additional check valve.
Jim Wallace - Principal Engineer, F128 - The engine fuel pump
does not have enough suction to pull fuel through the electric pump. The check valve is a
very low resistance one which bypasses the electric pump. Without the check valve and
bypass, the electric pump will keep the engine from getting fuel (unless you use it all
the time), and with a bypass and no check valve, the electric pump will just recalculate.
You can use a manual ball valve in the bypass, but you must bypass the electric pump so
the engine pump can suck.
Julius Setzer - I put a fuel recharge system on my 04. I put in
3 valves and 2 Ts inline ahead of the first filter, if I run out of fuel I close one
valve and open the other two. This hooks the fuel line to a 12 Volt fuel pump which I use
to pump fuel from the tank to the engine,after the engine been recharged I reverse the
valves so that the fuel goes through, with the 12 Volt pump off line.