[urq] Re: Upper Wastegate Hose on '83 Ur Quattro

[Ben Swann]

[... are you still seeing 1.9 bar manifold pressure?  If so, that is probably
why your FP is shutting off.  I just checked the IST docs ... they indicate
that for any RPM at or above 2500, a pressure of 1.9 bar will shut off the
fuel pump.  At RPMs lower than 2500 the ECU will shut the FP off at even
lower pressures ... down to a minimum of a shade over 1.2 bar at 1000 RPM
and below.

Someone may have cranked down the adjustment on the WG spring perch ... but
I've got a pet theory I've never verified ... a theory that closes the loop
with your original report.  I am pretty sure that if you sealed that vent
line in the upper WG it would turn the air trapped in the upper WG chamber
into a parallel spring that would effectively stiffen the WG spring and
raise the max boost pressure.  Could that hose you have on the vent be
pinched by any chance?  I had a similar situation on a 5kT where the line
sealed the upper chamber and led to overboost shutdown triggers ... 

Steve B
San José, Kaleefohnia (USA)
> 
> Turns out, the overboost cutout, if that is what is happening is still
> there, just not as prevalent as before.]

Steve,

This problem started happening after I did some minor service to fix an air leak that I identified.  There is an o-ring seal around the bottom of the IGLOO cover on the fuel distributor.  I repaired this air leak, as the o-ring was broken.  I sealed with RTV fixing this air leak.  Car ran better and started better, but then I noticed the cutout that I had not experienced before.

When I did the repairs, I had removed the turbo hoses, as I needed to adjust/repair the idle switch too.  Everything is sealed tight now.

I read that the intake air sensor could cause this problem.  

I think that I am still seeing 1.9 bar.  Wastegate diaphragm holds pressure.

I may still have an intake leak somewhere allowing the overboost.  I need to understand how the boost gets regulated a little better, as it is a different setup than the MC/5000 turbo which uses frequency valve to control upper chamber and lower chamber pressures.

Ben