Date: Sun, 13 Mar 2005 11:19:34 -0500
Reply-To: Greg Potts <Greg@POTTSFAMILY.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Greg Potts <Greg@POTTSFAMILY.CA>
Subject: Re: Fuel Pump Cavitating??
In-Reply-To: <a9060c3417686365963b21bdf0401640@mycommunitynet.net>
Content-Type: text/plain; charset=US-ASCII; format=flowed
Hi Aaron,
If there were a leak in the fuel filter or clamps where air could get
in; fuel would be getting out. You would see and smell such a leak. My
answer to question 1 would be "No.", air is not the problem.
If the fuel pump is noisy it's either working too hard, or very close
to worn out. Remember that in normal operation the pump has to push
against more than 30 PSI thanks to the pressure regulator. Testing it
with no load is not replicating actual working conditions, so it's not
surprising there is no noise. Try pinching the output fuel line to test
it with 30 PSI of back pressure and you will have better idea of its
operation in normal use. Do you know how much fuel pressure you have?
If the pressure is too high you may be stressing the pump and causing
it to get loud. Too much operation under overload conditions will cause
the pump to fail, so you will want to figure this out ASAP.
Suggestions, ranked in order of expense:
1. Verify that you have good fuel flow from the tank, as there could be
an obstruction in the screen inside the tank.
2. Test the pump with a 30-40 PSI load, to see if it gets noisy under
"normal" conditions.
3. Replace the fuel filter. (I'm assuming it's upstream from the pump
in your configuration)
4. Put a fuel pressure gauge in the fuel rail to verify pressure.
5. Test the system with a known good pump.
Helpful Anecdote
In the summer of 2003 a friend of mine put an FI 2L engine into his
1974 bus just before a trip out west. He suffered a number of problems
with this engine cutting out at odd times, where it would revert to
normal operation after a half-hour or so. It took him several days to
figure out the problem: It turned out that the problem was a collapsing
fuel line between the filter and pump. (Filter was upstream) He had
installed a 12" section of line in this location and the suction from
the pump was causing the line to deform and block fuel flow. Shortening
the 12" line to 2" solved the problem. Not sure if this applies to your
configuration but I didn't think it could hurt to pass the info along.
Happy trails,
Greg Potts
Toronto, Ontario, Canada
1973/74/79 Westfakia Conversion **Bob the Tomato** LY3H
1977 Sunroof Automatic L63H/L90D
http://www.pottsfamily.ca/westfakia
http://www.busesofthecorn.com
On 10-Mar-05, at 11:45 AM, Aaron wrote:
> Hello all.
>
> I've just finished a subaru transplant. In the process of doing
> everything else, I replaced all of the lines on top of the tank and to
> the fuel pump.
>
> Now I've got the engine in and running, but the fuel pump seems to draw
> in air from somewhere. It makes sounds like it is cavitating which it
> did not do before. Currently I haven't figured it out, but I am
> guessing air is coming in at the little plastic fuel filter unless it
> is coming from the tank. I've verified that my pump is ok. If I stick
> a 1/2" hose from the pump directly to a gas can, it works like a charm
> but it pulls it out (and back into the gas tank) so fast I can only run
> it for 30 seconds.
>
> Question 1)
> Is there a way that the source of the air could be the line coming from
> the fuel tank (with 4 gallons in the tank)? The van in sitting level.
>
> Question 2)
> What is the best way to stop air from getting sucked in? I've tried
> clamps, double clamps and a bunch of other things. I spent hours trying
> to figure this out and still am not any closer.
>
> I've considered it might be a crack in the fuel filter. I can't blow
> air through it though. I noticed that the plastic is very pliable and
> the hose clamp can cause deformation of the nipple, causing air to be
> drawn in. I tried for a long time to figure it out and can't. I blew
> air back into the tank to see if there was a blockage....nope.
>
> So any ideas of how to best troubleshoot/fix this? Sometimes it's the
> little things that get me!!!!
>
> Thanks!
> Aaron
>
>
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