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From: Steve Ayscue (no email)
Date: Thu Jun 08 2006 - 16:15:32 EDT
The Cummins (with electronic fuel injection on a Dodge Truck) uses the
electric pump as a lift pump to supply fuel to the electronic injection
pump. From what I'm told, the (electric) lift pump is necessary to supply
positive pressure to the injection pump to eliminate the strain of lifting
the fuel from the tank. Without the lift pump, the electronic injection pump
is documented to have a short life. I put gauges on the truck to monitor the
systems to keep me aware of the workings, and I'm on my second electric lift
pump. Without the fuel pressure gauge I installed, I would never have known
the lift pump was not functioning, unless I were to crack a line for
bleeding, straining the $$$ injection pump. (The electric lift pump is low
pressure, 4-12 psi) Early versions of the Cummins in the Dodge trucks had
mechanical injection pumps and mechanical lift pumps.
I use the Mityvac
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=39522 for
working on my old Mercedes Diesel's vacume systems as many things like the
transmission, door locks, and a/c system are controlled by vacume. I also
occasionally use the Mityvac to bleed brakes. While it's main function is to
pull a vacume, it can be used to create pressure (not sure how many PSI it's
capable of and the gauge that comes with it only measures vacume). By
pulling a vacume, similarly to bleeding brakes, one can bleed a diesel fuel
system from the return line.
Steve Ayscue
----- Original Message -----
From: "Courtney Thomas" <>
To: "Steve Ayscue" <>
Sent: Thursday, June 08, 2006 2:29 PM
Subject: Re: lv-ab: Fuel Filter Vacuum
> If the electric fuel pump on your Cummins [which engine ?] quits running
> would there be any consequence other than the engine halting ?
>
> Please educate me as to what the Mityvac is/does and how it would be
> deployed as a backup for the Cummins ?
>
> Appreciatively,
>
> Courtney
>
>
> Steve Ayscue wrote:
> > In doing some troubleshooting on an old Mercedes diesel, it has been
> > suggested to me to use a Mityvac hand vacume pump to suck the fuel
through
> > the return line to prime the system. My Cummins has an electric pump, a
300D
> > 5cyl diesel has a hand pressure pump, and the 300SDL 6cyl Mercedes has
> > neither, hence the hand vacume pump to suck the fuel (and air) through
to
> > prime. Also note that the electric pumps are prone to failure (the one
on my
> > Cummins runs continuously and I monitor it with a fuel pressure gauge).
A
> > Mityvac (with canister) could be a good backup plan.
> >
> > Steve Ayscue
> >
> > ----- Original Message -----
> > From: "Norm of Bandersnatch" <>
> > To: "Alan Lewis" <>;
> > <>
> > Sent: Wednesday, June 07, 2006 10:07 AM
> > Subject: RE: lv-ab: Fuel Filter Vacuum
> > Clip
> >
> >>I highly recommend an electric fuel pump between the tank and the Racor
to
> >>prime the fuel system, to drive the air out. Many a boat has come to
> >
> > grief
> >
> >>because of air in the fuel system. The only way to get it out is to
pump
> >>fuel through the system.
> >>
> >>Check out "Bandersnatch's Fuel System" in the archives to find out why I
> >>never have fuel problems.
> >>
> >>You don't have to re-invent the wheel.
> >>
> >>
> >>Norm
> >>S/V Bandersnatch
> >>Lying St Augustine FL
> >>
> >
> >
> >
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