5000CS TQ Hot Start Problems

Ben Swann bswann at worldnet.att.net
Fri Dec 6 11:10:49 EST 2002

[Hello out there,
My name is Jeffrey and I own an 1987 Audi 5000cs Turbo Quattro.
I am having hot start problems.]

Hot starting problem would not likely be due to faulty accumulator.  Is
your after-run fan/pump working running after heat soak driving?

[About three months ago the car did not start right away after I ran into a
store. The car was on a steep hill and there was a low fuel tank.
I got the car level and then it took a couple of minuets of cranking to get
it to start.
I have had trouble since then.]

You have replaced the injectors, correct?

System pressure regulator mounted in CIS fuel distributor may be dirty,
worn, or clogged.  Obtain a kit (or 2 in case you screw up) prior to
checking.  Try letting the system purge  by removing system pressure reg
and momentarily letting fuel flow for a split second - this unorthodox
method can be dangerous so be careful not to let too much fuel squirt out.
 It can be a good way to make sure any dirt has been expelled prior to
repairing/replacing the regulator assembly, and also making sure the spring
and seat have come out too -  Hold a rag underneat to catch,  14mm" wrench
to remove and install.   Don't mess with the stuff inside the regulator
under the allen screw unless you have exhusted other possibilities.

[After messing around I thought that now it might be the accumulator.]
 Nah!  Replace this after you have checked and replaced everything else.

[The Haynes book says in the fault diagnosis that it might be:

warm control pressure too high or too low]

Fuel Pressure tests may reveal, and be in order, but don't go there first,
since they can be troublesome.  Bad gas or water in the tank can mess up
the regulator, however.

[sensor plate / control plunger faulty]  Check for binding and that it
lifts smoothly through range of travel.

[Fuel or vacuum leak]  Definately rule these out first.  Injector o-rings
are big air leaks,  and injectors can bleed down, which can only be
observed by pulling them and watching them after they have been pressurized
- fuel can be observed weeping up the side of leaky ones
[leaky fuel injectors or low opening pressure] as above, it would be
appropriate course of action to replace them all if they are questionable.
[Incorrect mixture adjustment]  Yes, but this should not have changed
unless someone played with adjustment, or you have a vacuum leak.

[I am real sure there are no fuel leaks and have look hard for the vacuum
leak.]  We all do this, and find there are many more than obvious at first.

[The car runs great when it starts cold.]  Does it start in under 2-3

[I was staying away from that sensor plate I was warned it is touchy]  Have
you pulled the waffle boot, replaced filter and checked for debris?

[I pulled the spark plugs once and they were totally dry when I was hot
starting the car]  Sounds good, or do they show indication of lean running?

[The fuel pump works well
I have spark
The car starts right away when she sits over night or for about 6 hours and
totally cold.
Right now to get it to start hot I have to crank it about 20 or 30 secs or

I have had problem where ignition switch is not providing voltage to
ignition when cranking and engine catches after key is released  - bad
ignition switch?
[The starter will not take it much longer and the battery is going south.]
 Fresh battery may help.

[I did have it in "storage" for a month at Werners but they said they want
2000.00 just for starters.]  Maybe it needs an "Italian tunup" - fill tank
with fresh gas and injector cleaner and run the "demons"out of it.

[I am fairly mechanically minded and have the standard tools.
Please let me know where I could continue.
My current plan was to replace the thermo sensors that are on the cooling
manifold.  then I was going to get a new regulator.]  The multi-funtion
sendors can be troublesome.

[Then perform more little tests.
I am hoping that it will not be the electronic control unit.
$1300.00 for a new one.]

Ahhhh (scream) watch your wallet - don't shotgun or let others do this to

To check the ECU and other subsystems you can pull codes by inserting fuse
in top of fuel pump relay for a second and then removing.  Diagnostics
codes will be displayed on the instrument console as series of flashing
engine check light.  A series of 4 flashes four times interspaced with a
single long flash indicates all is well with ECU and no fault have been
detected by FI subsytems or components.  If you see something else I or
other knowledgable listers can help you from there.

I hope the $2500 you mentioned in your original post was the cost of the
car when it was running perfectly.  Sorry, rant mode off.

[Thank you for your time.


Welcome, and hopefully we can help you get and keep the car running well
without you taking out a second mortgage.


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