Date: Mon, 31 Mar 2008 09:50:45 -0800
Reply-To: Mark Drillock <drillock@EARTHLINK.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Drillock <drillock@EARTHLINK.NET>
Subject: Re: Heads back on, runs OK and dies
In-Reply-To: <4d1b79350803310930g6f0c5342r3b74d11dc66c00f3@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Jim, the fuel pressure regulator has 3 fuel hoses going to it. Of these
2 come from the fuel rail on each head. The 3rd is the return line back
to the tank. It is on the round end, opposite the end with the small
vacuum hose.
The fuel pump runs full blast at all times while the engine is running.
Most of the fuel returns to the tank from the regulator after passing
through the fuel lines to the heads. A small amount is injected at idle
but more is injected at higher loads and less is then returned to the
tank. The fuel used at maximum load can never exceed the amount being
returned to the tank at idle or there won't be enough fuel to keep the
pressure constant at full load.
VW gives us a spec for the minimum allowed fuel quantity to be returned
to the tank. If we have at least this much we then know the pump,
filter, and fuel passages from the tank are sufficient to keep up with
the fuel demands.
It is best to check the fuel pressure from that "T" port while the fuel
quantity test is being performed because we need to know that the fuel
system can provide both the required quantity AND pressure AT THE SAME TIME.
Mark
Jim Felder wrote:
> Thanks, Mark. I have a graduated container I can use for this test...
> but specifically, which tube? I don't know the fuel system very well
> because I have never had to do a single thing to it. I see where there
> is a takeoff on the tee where it looks like you could attach a gauge,
> which is where I was headed if you had not offered this test.
>
> Jim
>
> On Mon, Mar 31, 2008 at 11:16 AM, Mark Drillock <drillock@earthlink.net
> <mailto:drillock@earthlink.net>> wrote:
>
> Why not do a simple fuel delivery test? Remove the return line from the
> pressure regulator and run a short piece of hose from the regulator
> return fitting to a small container. Then run the fuel pump for 30
> seconds. You should get 1 pint or 500 ml of fuel, at least. Or if you
> run the engine and fuel continuously comes out the return fitting then
> you know to look for some other problem.
>
> If the above fuel test passes my guess is that you may have an intake
> valve lifter problem, maybe too tight. Time for a compression test to
> find which cylinder to loosen the adjuster on.
>
> Mark
>
> Jim Felder wrote:
> > On Mon, Mar 31, 2008 at 7:32 AM, Benny boy <huotb@videotron.ca
> <mailto:huotb@videotron.ca>> wrote:
> >
> >.............
> >
> > I'm thinking fuel at this point, as it starts fine, than just
> gets weaker
> > and weaker over ten or fifteen seconds and then dies like it's
> starving for
> > fuel. I also intend to blow-back into the tank in case it's
> settled debris
> > from the gas tank. The pump and filter are relatively new.
> >
> >>
> >> Last, and sorry to say, Vanagon head job is an art in some ways.
> I have
> >> fix
> >> badly done job more than once. I can change Subi / Honda /
> Toyota head
> >> gasket with my eyes close.... Any Vanagon heads job still need
> my full
> >> concentration.
> >
> >
> > Right, it's more difficult than any other head I can think of.
> Sealing
> > issues everywhere.
> >
> > Thanks,
> >
> > Jim
> >
> >>
> >> Best luck to you
> >> Ben
> >>
> >
>
>
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