No start condition - 1988 90Q - THIRD UPDATE

[Radek]

Hi guys;

Thanks to all who chimed in, we managed to get the motor to run briefly by removing the igloo and pulling the air measuring plate up with pliers.  So it seems to be a fuel issue, probably somehow connected to the throttle butterflies not operating properly.  Planning to dismantle throttle body tomorrow, also double check for vacuum leaks and change fuel filter.
Thanks.

Radek


----- Original Message ----- 
From: Radek 
To: quattro at audifans.com 
Sent: Tuesday, August 02, 2011 10:47 PM
Subject: Fw: No start condition - 1988 90Q - SECOND UPDATE


Played with fuel pressure regulator (attached a vacuum pump to it) - no difference.
Changed idle stabilization valve - no difference.
Advancing ignition timing seems to help - instead of a single fire we get two or three, but still does no start.
An observation - does not fire at all with fully depressed throttle, but will fire with throttle off.
When firing, sometimes loud knocking can be heard, seems to come from the intake manifold - backfire?

Also, throttle body butterflies seem to be weird.  The small one opens and closes smoothly, but the large one only opens fully in one shot at WOT then, when slowly released, snaps back with a loud ping.  Is it supposed to work like this?  All levers and springs seem to be in place.

Planning to switch ECU tomorrow, hate to think about contortions necessary to get deep into the passenger well.
Cheers;

Radek.


----- Original Message ----- 
From: Radek 
To: quattro at audifans.com 
Sent: Tuesday, August 02, 2011 12:21 PM
Subject: Re: No start condition - 1988 90Q - UPDATE


Fully charged battery overnight.  Blinked out codes - nothing.
Replaced ignition cap, rotor and wires with good looking old set - got car to sputter a bit.  It seems to catch a bit initially and then no more.  It is actually catching when cranked with foot off the gas - with throttle open, nothing at all.
Any ideas?  Is there a way to check fuel pressure on these engines (NG)?
Radek.


----- Original Message ----- 
From: Radek 
To: quattro at audifans.com 
Sent: Monday, August 01, 2011 9:46 PM
Subject: No start condition - 1988 90Q


In  need of help again, my son's 90q is out of commission again.
Here is what he reported:
when trying to start the car, at the first or second crank he heard a bang (a snap, something sounding mechanical) and smelled something weird under the hood.  The smell, he said, smelled of friction.
The car kept cranking, but no start.  Came back home on a flatbed.

Here is what I checked till now:
- starter cranks the engine
- timing belt is OK
- valve train is moving (took rocker cover off to see if sprocket is not sheared)
- has good compression
- timing belt alignment is OK (crankshaft to camshaft)
- distributor turns
- smells of gas when cranked
- seems to have spark (checked with wire touching enging block)
- coil resistance checks out OK
- Hall sensor works (blinks a diode)

Where to look next?  I'm going to blink out error codes tomorrow, mosquitoes chased us out tonight.
TIA

Radek