Frustrations set in.. prematurely? (SAME 84 start issue)

[Johnny B]

Well at this point I really have no choice but to rip in to the fuel system with a pressure tester. This start issue absolutely makes zero sense to me and I really have no other direction to go in. To be honest, I give it two weeks before I tear this bitch down for parts on my ur-quattro (as at this point I dont think I'll find the problem. The PO noted 12 years of trying to find this, countless tests and the guy was no dummy, several of the ur-q owners know him quite well). Sorry to get so disgruntled but I have literally crawled to hell and back again on this thing and found absolutely no problems, and the symptoms continue. Without technical know-how, or the budget to support replacing everything fuel related, I'm totally lost. 

So, just to recap: Cold start takes 3-4 tries before firing. Warm start will take 1 or 2 tries before starting. Both have the same symptoms once started: Bogs when you throttle, will not allow you to drive. When warm this lasts 5-10 seconds, when cold this lasts a bit longer, 30-40 seconds. Symptoms are the same if you drive for 30 mins, shut the car off, and fire right back up 30 seconds later. Same bogging, same symptoms, no change. The issue is lean, for whatever reason it does not get enough fuel. 

Screams vacuum leak right? Well, considering my idle is 100% rock solid just shy of 1k, never wonders, good power through to red line, and after a complete soak down of chemtool, I dont think this is my problem. That is, unless there is a hidden massive vacuum leak that takes 5 seconds to re-close when already hot. Not likely, and I really dont know where else to look. 

Cold start valve would not effect throttle once started. The coolant temperature sensor for the ECU has been replaced. The idle & WOT switches have been tested. The injectors & seals are new, all vac lines & connections have been replaced, full tune up performed + a fresh rebuild on the engine less then 30k ago. Accumulator & check valve have been ruled out with bypassing the FP relay. This all does not compute with my starting issue. 

Shit. Any suggestions on where to drop this off in Norcal appreciated. 

Johnny





> Date: Mon, 16 Aug 2010 08:25:09 -0500
> Subject: Re: Re. Narrowing down my start issue (84 4kq)
> From: josh at spiny.com
> To: cody at 5000tq.com
> CC: benswann at verizon.net; quattro at audifans.com; pre95 at live.com
> 
> I'll second that. It's critical to know that the pressure is right, and that
> the DPR or warm up regulator is doing it's job. You can spend lots of money
> and time chasing this, or you can spend $90 or so for a fuel pressure tester
> and know for sure what's wrong.
> 
> 
> 
> On Sun, Aug 15, 2010 at 6:52 PM, John Cody Forbes <cody at 5000tq.com> wrote:
> 
> > Check. The. Fuel. Pressures.
> >
> > -Cody (mobile)
> >
> > On Aug 15, 2010, at 4:22 PM, Johnny B <pre95 at live.com> wrote:
> >
> > >
> > > Well thanks for the great tip! I swapped the fuel pump relay for the fan
> > relay from my ur-quattro and no change on start (though the fuel pump runs
> > on a constant as you said it would, I let it run 3-4 seconds before trying
> > to start, same symptoms. I put the fuel pump relay back in Huw!). Very
> > frustrating to say the least... I'm, not really sure where to go from here
> > regarding this start issue. If its not a lack of residual fuel pressure, and
> > not a vacuum leak (just replaced all formed vacuum tubes & all cloth covered
> > vac lines, checked the entire system over), and knowing it had this same
> > issue prior to new injectors being installed (this problem carried over from
> > before the engine rebuild, which included all gaskets, rings, cylinder head
> > rebuild, and fuel injectors + seals).. where do I go from here?
> > >
> > > Starting to get discouraged... if you give it any throttle over a light
> > touch of the gas pedal for the first minute (when cold) it bogs and wants to
> > die. Does the same when hot but only for the first 8-10 seconds... Im
> > thoroughly stumped. Car has great power through the RPM band, top & low end
> > are fine, idle is always rock solid just shy of 1k, cannot source any vac
> > leaks with the chemtool when warm or cold... not really sure what else to
> > check. Once the start symptoms pass, the car is perfect.. it doesnt drive
> > like it has any issues at all which just adds to my frustrations.
> > >
> > > Thanks guys, I'm not giving up hope but definitely understand why so many
> > throw in the towel and go EFI.
> > >
> > > Johnny
> > >
> > >
> > >
> > >> Date: Sat, 14 Aug 2010 23:59:06 -0400
> > >> From: audi at humanspeakers.com
> > >> To: benswann at verizon.net
> > >> Subject: Re: Re. Narrowing down my start issue (84 4kq)
> > >> CC: quattro at audifans.com; pre95 at live.com
> > >>
> > >>
> > >>> Anyway, for purposes of trouble-shooting in the indefinate future you
> > probably should
> > >>> just keep a fan relay installed in place of the normal FP relay.
> > >>
> > >> Keep in mind that this disables a critical safety feature - your fuel
> > >> pump will keep running even if an accident kills your engine.
> > >>
> > >> Also, you will have no overrev protection.
> > >>
> > >> Just to keep in mind while playing this game.
> > >>
> > >> --
> > >> Huw Powell
> > >>
> > >> http://www.humanspeakers.com/audi