Re: Relay, Stumped & 4ksq won't start

[luis@odf.ucsd.edu (Luis Patino)]

Well, I have solved my 4ksq warm-start problem - finally. The problem was
the fuel pump relay. I suggest that all of us whose cars refuse to start
when warm replace their relays first (borrow one from a friend to test).

The problem is that a bad relay may only activate the pump after the motor
is already runing. If the fuel lines are cold the engine will still start
since there's no vapor lock to overcome, but if they get hot the residual
pressure on its own can not get the engine started. You'll see that it is
in fact the relay when you turn the ignition key to the on position (without 
cranking the engine) and do not hear the fuel pump running to pressurize the
sytem. I had noticed this oddity myself, that my new 4ksq did not behave like
my GTI in that the fuel pump did not come on with the on position like with
the GTI, but oh silly me, I just assumed that was because Audis were
different. Well, they aren't: they all have K-Jetronic systems working in
exactly the same way. 

I discovered this because the relay finally died, stalling the motor in the
middle of a busy street at rush hour. Luckily, I thought of a relay 
malfunction and bridged the pump, so I got myself out of danger yesterday.
Today, after I put the new relay in, the instant I heard the pump come on 
without having turned the key all the way to the crank position I knew that
the new relay would finally solve the problem. It sure did!! 

Audis are great mechanichally, so always supect their 12-year-old electronics 
first, especially that POS Kraftstoffpumperelai!!!

Please let me know how this helped.

Luis
85 4ksq 133k mi - and now running like new :)