Date: Mon, 3 Mar 2014 20:32:18 -0800
Reply-To: "SDF ( Scott Daniel Foss )" <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: "SDF ( Scott Daniel Foss )" <scottdaniel@TURBOVANS.COM>
Organization: Cosmic Reminders
Subject: Re: Residual Fuel Pressure: hold for 1 hour?
In-Reply-To: <CAB2Rwfg8J7905OtM+ZbRZQ--LuSpbioW7rV_=Tcg41c7pi4Msw@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Hi Neil..
perhaps you have ..what I like to do in a case like this is have a fuel
pressure gauge on it full time..
so when it won't start hot ..
I can tell if it's a fuel pressure issue or not.
my hunch is fuel pressure is OK then ..
and it's something else...not enough injector hold-open time perhaps.
in all cases I would be inspecting carefully what is inside the fuel filter.
It's great to have a spare fuel pump, fuel pressure regulator and ECU to
try.
I might even rig my own fuel pump cheater switch ..if I thought 1 second
of pre-run was insufficient pre-run time.
If it was cranking and not firing up hot ..
as a test I might dump a small cup of raw gas down the intake and see it
that makes it go VROOOOMMM ...
thus confirming it's some for of not enough fuel ..
either fuel being available ..
or not enough fuel pressure ..
or not enough injector pulse.
I often try a whole other fuel source...separate tank on the rear floor
of the van for example..
just in case it's a fuel pick-up restriction issue.
noisy fuel pump when hot doesn't sound right.
Gots to have a spare known-good fuel pump. Tain't possible to do
effective home mechanicin' without one.
'why'...
how about it's a 20 year old fuel pump with thousands of hours on it and
it's tired ..
or how about 'it's just a blockage or leakage of fluids or electrons' ..
and it IS that for sure !
On 3/3/2014 7:46 PM, Neil N wrote:
> Hi Scott.
>
>> Do you normally start the van by turning the key to *ON* ( not start )..
>> then listen for the fuel pump to run, aand then shut off...before
>> turning key to 'start' ??
> I always turn key to ign. on, listen for pump, look for lights, then
> start the engine. The Jetta Motronic engine management primes the fuel
> pump *very* briefly. Like 1 second.
>
> Engine cold, it always starts the first time and drives fine. If I
> drive it til it is up to temp, shut engine off, then try to start it
> 1/2 hour - 45 later, (engine slightly warm), it won't start the first
> try. It just cranks and cranks. If i keep cranking, it might "cough"
> once or worse, barely run, stall, then become really hard to start.
> This is consistently repeatable. For some time now, the fuel pump
> tends to get quite noisy on hot days so yes. For that reason alone, I
> felt I needed to address this.
>
> During todays tests, with engine only partly warm, if I use my fuel
> pump relay bypass switch to run the fuel pump for 5 seconds or less,
> it instantly pressurizes to 40 PSI. If I shut pump off after the 5
> second mark, pressure drops very quickly to zero unless I clamp off
> the fuel supply hose. Engine cold, if I run pump for only 1 second
> then turn it off, the system holds pressure (residual pressure) just
> like it should. All this seems to support the above conditions. I just
> can't figure why the fuel pump is behaving like this.
>
> I'm about certain the fuel pump is at fault. Yes I can replace it but
> assuming the check valve is at fault, I'd really like to know why it's
> behaving this way.
>
>
>
> On 3/3/14, SDF ( Scott Daniel Foss ) <scottdaniel@turbovans.com> wrote:
>
>> Do you normally start the van by turning the key to *ON* ( not start )..
>> then listen for the fuel pump to run, aand then shut off...before
>> turning key to 'start' ??
>> I think you are chasing a mostly non-problem.
>
> --
> Neil n
>
> Blog: tubaneil.blogspot.ca
>
> '88 Westy http://tinyurl.com/c8rlw6p
>
> '81 VanaJetta 2.0 "Jaco" http://tubaneil.googlepages.com/
>
> Vanagon VAG *Gas* inline-VR Engine Swap Group:
>
> http://tinyurl.com/d7gd5ej
>
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