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Re: Wierd starting problems
Well, I called BLAUfergnugen today (very helpful tech info line), and th
e guy I talked with seemed to know a lot about my car. I told him what the pro
blem was, and he told me that he thought the problem was the fuel pump check va
lve. He also said it could have been some leaking injectors. He seemed to kno
w what he was talking about, and seemed fairly confident that this was the prob
lem. He said he's seen these symptoms many times before, and he said, 9 out of
10 times it's the fuel pump check valve.
I would think this problem (fuel system not holding pressure) would be a
"hard-to-start" (ya gotta crank it for several seconds) problem, as op-
posed to a absolutely-will-not-start problem. But then again, it is an
Audi . . . Your book (Haynes, Bently, etc.) should have a time chart for
residual fuel system pressure as a function of time, or just a simple
datum like "after 30 minutes pressure should still be at least 2.2 bar".
Very easy to test, with the "right" tools . . . your friendly neighbor-
hood Audi dealer/mechanic should be able to do this for ya for about
15 minutes' worth of labor if you don't have all the odds'n'ends to do
When the system pressure leaks down (leaky injector, check valve, etc.)
then the fuel system is much more susceptible to vapor lock (gas boils
away, air bubbles in fuel injectors, etc), all of which "eventually"
cure themselves if you crank long enough to re-pressurize the system
(should take fraction of a second) and then "bleed" out the air bubbles
(could take quite a while at cranking speeds; this is the basic "rough"
running for a coupla seconds after starting that is also symptomatic
of all these woes).
BTW, Robert, I asked about this "hot start pulse relay" and he told me
that this relay is only on older models and is not on my car. BTW, to all of y
ou just tuning in this is on a 5000CSTQ and the problem is the car will only st
art if the engine is cold (and I'm talkin ice cold here).
Eminently believable. The Hot Start Pulse Relay is a real Krock, as is
the Control Pressure Regulator and the Aux Air Valve and all the other
warts grafted onto the engine over the years before they finally went
full-auto and just gave the ECU total control over everything, resulting
in a much-simpler APPEARING engine compartment (and of course a much
greater susceptibility to "electrical" problems like bad grounds, poor
crimp connections, flakey sensors, etc.)
P.S. Not to overlook the obvious, but starting fluid ("ether") makes
a wonderful addition to your traveling kit...if the car won't
start, a quick shot of ether will tell ya instantly whether or
not it's fuel-delivery-related (if the engine goes VROOM!!!Cough
then you clearly have a starting-enrichment problem of some sort,
if the ether doesn't turn the engine over, you have no ignition
(ether "burns" if you look at it cross-eyed, so even a terminally-
wimpy ignition/spark will set it off!).
P.P.S. Finding a way to insert the ether into the engine intake tract is
left as an exercise for the reader . . . (hint: it ain't easy on
some of those cars out there!)