Holy cow! Thanks a lot! I will try this ASAP!!

chris

> Often the hot start problem is due to overheating the fuel in the lines
> above the manifolds. Try shielding the lines (the car originally came with
> a rubber cover around the lines) - my '87 has a similar problem and since
> I'm in the process of reinstating the A/C...and it's getting hot out
> there...I'm going to be insulating the lines. I'm making a cover (like the
> tattered original rubber boot that was in the car when I bought it) out of
> reflective foam core insulation - the stuff that some hot rodders use for
> firewall/underhood insulation. The basic problem is that the 10v engines
> have both hot and cold manifolds on the same side of the engine - and when
> parked, the exhaust manifold heats the intake manifold, and the fuel lines
> above (uh..."heat rises" was a hard lesson to learn?) the 20v changed to a
> better setup to allow for a Hot and Cold side. Make sure that the injector
> cooling fan is working as well - the thermo-switch is located on the heat
> shield at the back of the head over the wastegate (grounding the connection
> should start the fan).
> Another thing I'm tackling is that the intake air temp sensor is located in
> the intercooler - I'm moving it to just behind the throttle body on the
> intake manifold (when I get around to installing the bypass valve....etc.
> etc. etc.). The different location of the sensor will give a better
> representation of startup air temp to the ECU - don't know if that will make
> as much of a difference as the shielding.
> All that fails, check fuel pressures/fuel pump check valve/injector
> condition/etc. I have heard that some times the crankshaft reference sensor
> gets lazy when hot - that would throw a code you could read.
> Cheers!
> Steve Sears
> 1987 Audi 5kTQ
> 1980 Audi 5k
> 1962 and '64 Auto Union DKW Junior deLuxes
> (SPAM Blocker NOTE: Remove SHOES to reply)
>
> "cp" <dont@email.me> wrote in message news:M0Bqc.12179$RM.9044@edtnps89...
> > Steve, I have another question for you.
> > This Audi has a (maybe I should say THE) warm
> > starting problem. I looked it up on this ng and found
> > many posts, the first one was mine from years back
> > when I had a similar audi, I forgot it had the problem.
> > After reading most of the posts I'm still not sure where
> > to look. The car starts perfectly when cold or hot but if
> > it has been standing for 30-60 min it will refuse to start, it
> > sounds like a dry start. It will start all of a sudden after
> > cranking for a minute or two (with breaks of course). The
> > idle will be unsteady and the engine sometime turns off. When
> > started hot or cold it runs perfectly. Any idea where I should
> > start looking for this problem? I have a bit of mechanical
> > competency
> >
> > Thanks in advance for any help,
> > cp
> >
> >
>
>

 

> Holy cow! Thanks a lot! I will try this ASAP!!

Hi chris,

mine had a hot start problem and the autoelectrician found a faulty
valve near the fuel pump. Once he replaced that, the problem was gone.
He said the valve maintains the pressure in the fuel system for some
time after the engine is switched off. This pressure seems to be
necessary to start the engine when hot.

Unfortunately, he messed up the fuel gauge, so that I didn't realise I
was running out. He repaired that now (for free), but it seems some
dirt got cought somewhere in the tank close to the pump, so that the
car starts to cut out when the tank is still 1/3 full. Have to find
the time to go back at some stage.

Good luck,

Christoph

> > Often the hot start problem is due to overheating the fuel in the lines
> > above the manifolds. Try shielding the lines (the car originally came with
> > a rubber cover around the lines) - my '87 has a similar problem and since
> > I'm in the process of reinstating the A/C...and it's getting hot out
> > there...I'm going to be insulating the lines. I'm making a cover (like the
> > tattered original rubber boot that was in the car when I bought it) out of
> > reflective foam core insulation - the stuff that some hot rodders use for
> > firewall/underhood insulation. The basic problem is that the 10v engines
> > have both hot and cold manifolds on the same side of the engine - and when
> > parked, the exhaust manifold heats the intake manifold, and the fuel lines
> > above (uh..."heat rises" was a hard lesson to learn?) the 20v changed to a
> > better setup to allow for a Hot and Cold side. Make sure that the injector
> > cooling fan is working as well - the thermo-switch is located on the heat
> > shield at the back of the head over the wastegate (grounding the connection
> > should start the fan).
> > Another thing I'm tackling is that the intake air temp sensor is located in
> > the intercooler - I'm moving it to just behind the throttle body on the
> > intake manifold (when I get around to installing the bypass valve....etc.
> > etc. etc.). The different location of the sensor will give a better
> > representation of startup air temp to the ECU - don't know if that will make
> > as much of a difference as the shielding.
> > All that fails, check fuel pressures/fuel pump check valve/injector
> > condition/etc. I have heard that some times the crankshaft reference sensor
> > gets lazy when hot - that would throw a code you could read.
> > Cheers!
> > Steve Sears
> > 1987 Audi 5kTQ
> > 1980 Audi 5k
> > 1962 and '64 Auto Union DKW Junior deLuxes
> > (SPAM Blocker NOTE: Remove SHOES to reply)
> >
> > "cp" <dont@email.me> wrote in message news:M0Bqc.12179$RM.9044@edtnps89...
> > > Steve, I have another question for you.
> > > This Audi has a (maybe I should say THE) warm
> > > starting problem. I looked it up on this ng and found
> > > many posts, the first one was mine from years back
> > > when I had a similar audi, I forgot it had the problem.
> > > After reading most of the posts I'm still not sure where
> > > to look. The car starts perfectly when cold or hot but if
> > > it has been standing for 30-60 min it will refuse to start, it
> > > sounds like a dry start. It will start all of a sudden after
> > > cranking for a minute or two (with breaks of course). The
> > > idle will be unsteady and the engine sometime turns off. When
> > > started hot or cold it runs perfectly. Any idea where I should
> > > start looking for this problem? I have a bit of mechanical
> > > competency
> > >
> > > Thanks in advance for any help,
> > > cp
> > >
> > >
> >
> >
>

--
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Thanks a lot Christoph, I will check this out. The problem seems
to happen more frequently now. Starts up perfectly when cold, but when
warmed up sometimes the RPM wavers and the engine turns off, when that
happens, I can't start the car for like 10 minutes, if I "push" start the car, down
hill in gear it starts perfectly, but not if I try with the key, it sounds like it's trying
to start dry. When it does start, I have to keep my foot on the gas to keep
it from turning off. I'll try your suggestion, first I have to try Steve Sears'
suggestion.

Thanks again!
cp

> mine had a hot start problem and the autoelectrician found a faulty
> valve near the fuel pump. Once he replaced that, the problem was gone.
> He said the valve maintains the pressure in the fuel system for some
> time after the engine is switched off. This pressure seems to be
> necessary to start the engine when hot.
>
> Unfortunately, he messed up the fuel gauge, so that I didn't realise I
> was running out. He repaired that now (for free), but it seems some
> dirt got cought somewhere in the tank close to the pump, so that the
> car starts to cut out when the tank is still 1/3 full. Have to find
> the time to go back at some stage.
>
> Good luck,
>
> Christoph

 

Oh yes, when this problem happens there starts being hot oil stench.

cp

> mine had a hot start problem and the autoelectrician found a faulty
> valve near the fuel pump. Once he replaced that, the problem was gone.
> He said the valve maintains the pressure in the fuel system for some
> time after the engine is switched off. This pressure seems to be
> necessary to start the engine when hot.
>
> Unfortunately, he messed up the fuel gauge, so that I didn't realise I
> was running out. He repaired that now (for free), but it seems some
> dirt got cought somewhere in the tank close to the pump, so that the
> car starts to cut out when the tank is still 1/3 full. Have to find
> the time to go back at some stage.

 

Hi,

> Thanks a lot Christoph, I will check this out. The problem seems
> to happen more frequently now. Starts up perfectly when cold, but when
> warmed up sometimes the RPM wavers and the engine turns off, when that
> happens, I can't start the car for like 10 minutes, if I "push" start the car, down
> hill in gear it starts perfectly, but not if I try with the key, it sounds like it's trying
> to start dry. When it does start, I have to keep my foot on the gas to keep
> it from turning off. I'll try your suggestion, first I have to try Steve Sears'
> suggestion.

I forgot to mention that mine behaved like a flooded engine when it
eventually came on. That's why the mechanic in the Audi garage
suspected the fuel injectors (he said they tend to leek into the
cylinders and cause the flooding). Since new fuel injectors are quite
expensive, he suggested I should ask the auto-electricians (Bosch
service centre) whether they couldn't clean the injectors. There, they
didn't even take the injectors out since the engine started fine after
this valve was replaced.

The problem was worst on warm days with the car parked in the sun
about 10 to 20 minutes after I stopped. It was really like flooded. I
was always able to get it started eventually. I normally started as
normal, just left it turn for 15 to 20 seconds without touching the
acelarator. I then gave it a bit of a rest (I was very worried the
starter might go) and tried again. Normally it would start after
another 10 to 20 seconds, with the typical complaints of a flooded
engine (irregular at first, then slowly faster and eventually run fine
with a bit of fuel smell). I still don't have any idea why that could
be caused by a loss of pressure in the fuel system...

But it runs fine now.

> > mine had a hot start problem and the autoelectrician found a faulty
> > valve near the fuel pump. Once he replaced that, the problem was gone.
> > He said the valve maintains the pressure in the fuel system for some
> > time after the engine is switched off. This pressure seems to be
> > necessary to start the engine when hot.
> >
> > Unfortunately, he messed up the fuel gauge, so that I didn't realise I
> > was running out. He repaired that now (for free), but it seems some
> > dirt got cought somewhere in the tank close to the pump, so that the
> > car starts to cut out when the tank is still 1/3 full. Have to find
> > the time to go back at some stage.
> >
> > Good luck,
> >
> > Christoph
>

--
Important: Emails sent to me which contain my full name
in the "to:" or "cc:" field will bypass my spam filter.
With most programs "Reply" should do the job.