Fuel Pressure and Pump?

[Rodney Fulk]

You MIGHT have to..

-----Original Message-----
From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
Behalf Of Whit
Sent: Friday, January 18, 2002 10:50 PM
To: diy_efi at diy-efi.org
Subject: RE: Fuel Pressure and Pump?


I've been looking at the pictures of the pump in my service manual and the
actual pump looks like a pretty standard piece.  I'm thinking it can't be
too hard to buy a bigger pump and tweak it to fit.  I wonder if I would need
to increase the tubing and fuel lines as well to get the full advantage of
the bigger pump.
>
>
> As an add on to this.. A friend had an inline pump added to his
> normal flow
> for a NO2 system. Within a very short period of time (In a months
> time) the
> in tank pump disintegrated for some reason and this took out the
> inline pump
> as well. I would think a new inline pump is in order. It is more
> then likely
> that the current pump is far less then is needed.
> I know they do size the pumps for the motor so that you don't
> have too big a
> pump. Otherwise if you have too big of a pump the gas will get too hot and
> this will effect your engine. The fuel pump uses the fuel to cool it.
>
> SOME in tank fuel pumps are pretty universal. I have a fuel pump
> for my LT1
> caprice that is for a '98 Super Charged Bonneville. Puts out 50gph instead
> of the 35gph pump my original pump put out. I won't likely
> install it until
> I am a little closer to needing it but with a 23 gallon tank in
> my car I am
> guessing the fuel won't get overly warm if I run it for a little while...
>
> My guess is your pump is no where near the 35gph the caprice has and my
> caprice pump is not overly hard to overpower with a few mods...
>
> -----Original Message-----
> From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> Behalf Of Shannen Durphey
> Sent: Thursday, January 17, 2002 9:39 AM
> To: diy_efi at diy-efi.org
> Subject: Re: Fuel Pressure and Pump?
>
>
> In this case, it sounds like the factory pump may be insufficient.  Is the
> factory LT1 regulator still on the fuel rails?  If it is not damaged, then
> it
> should be regulating pressure to factory levels, provided there is
> sufficient
> fuel volume.
>
> One quick test to check the pump's ability to provide pressure would be to
> pinch
> the return line and watch the pressure rise on a gauge.  If it
> does not rise
> considerably, the pump is not going to work.
>
> You should also check volume.  You can do this indirectly by driving with
> the
> gauge installed and watching pressure changes.  Accelerate, power brake,
> drive
> up a large hill.  If the pressure is consistently at 35 psi, and the above
> "pinch off" test indicates that the pump can build pressure, then you may
> have a
> bad regulator.  But if fuel pressure drops way off, then insufficient fuel
> is
> being delivered to the engine.  Providing the fuel filter is not plugged,
> the
> pump would be the most likely suspect.
>
> If the diagnosis pointed to the tank, I would first try to replace the
> in-tank
> pump with something able to provide enough fuel.  I've had to
> troubleshoot a
> few
> draw-through, two pump systems, and the in tank pump can sometimes present
> considerable restriction.  If the in tank pump can provide a
> large volume of
> fuel at low pressure, then a two pump system is a reasonable option.  But
> using
> an in-line pump to draw fuel out of the tank can cause problems, imhe.
>
> Shannen
>
> Manuel Desantos wrote:
> >
> > You can run a second in-inline pump with the stock pump.
> > I'd get an adjustable Fuel Pressure Regulator.
> > You can also try and run the in-line and turn off the in-tank pump and
> > see if there is enough flow through the in-tank pump.  If there isn't
> > enough flow then I'd remove the in-tank pump and just run an in-line.
> >
> > -----Original Message-----
> > From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org] On
> > Behalf Of Whit
> > Sent: Friday, January 18, 2002 11:37 AM
> > To: diy_efi at diy-efi.org
> > Subject: Fuel Pressure and Pump?
> >
> > I'm running an LT1 in my 89 Jeep cherokee and am having fuel pressure
> > problems.  I am wondering if the stock fuel pump will do the trick.  The
> > stock pump was meant to run FI on the Jeep at about 35 lbs.  After
> > intalling
> > the motor it is still running about 35 lbs and I understand the LT1 is
> > supposed to run in the mid 40s. I bought a new regulator but my gut feel
> > is
> > that the stock pump is either inadequate or it needs to be replaced.
> > Any
> > have exprerience here?  What are options here?  Can I run a second
> > inline
> > pump?  If so, do I need the stock pump at all?
> >
> > Thanks,
> > Whit
> >
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> >
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