86' 5000 CS Turbo Will not warm start...

[Tripod]

Car starts fine when cold. Drives normally from a few to many miles, shut off car and try to re-start. Engine cranks but does not start or show any signs of attempting to start. Wait until car cools down and starts immediately with no signs of fouling or sputtering. Runs normally until engine is shut off and symptoms re-appear.

Coil ? Relay(s) ? Fuel ?

[DoctorD15]

got this from another forum, but this is waht this guy had to say....

start quote

"Typicaly", hot start problems (Hot, as in the fuel system has had time to heat soak after stopping, as opposed to trying to start immidiatly after stopping ) are becuase the fuel system won't hold is pressure when you shutdown when warm.

If fuel system pressure isn't kept up, fuel in the injector lines vaporizes easier when the hot engine is shut down, making the next start hard.

Fuel pressure dropping too quickly/fuel vapourization after shutdown can be becuase of any or all of the following:

1) Injectors leak
2) Accumulator is dead
3) Check valve at pump doesn't check
4) Injector cooling fan inoperative, or not pulling in cold air from down by the subframe

If that's too much to fix, I've heard of some that have wired a pushbutton switch to fire the cold start injector sensor. That lets you 'manually' force cold start injector to spray when hot. That will give some fuel for the motor to start on instead of vapours, and save your starter from getting trashed...

end quote

Thats what he had to say, but try going to this

site...SJM Autotechnik, Audi Parts Specialist, 503-244-2834, Audi Quattro Parts, VW Parts, BMW Parts

Its got a ton of good info on....just scroll down to advnaced search and search your warm start issue. Hope this helps.

[Tripod]

Thanks for your ideas. Information is good.

I have had the mis-pleasure of working on Bosch k-jetronic about 25 years ago. I bought an engine-less VW Rabbit from a bankruptcy case and an engine from a salvage yard. Installed the engine, put in some fuel and started it up. Everything was good for about 30 seconds. As it turned out, the gas tank was contaminated with moisture, rust, dirt, etc. After boiling out the tank, flushing the lines, replacing the filter, etc., the fuel system was never really fixed. I replaced the warm-up regulator, adjusted the sensor plate, tested the pressure regulator, checked the amount of fuel flow with each injector, tested the cold start injector as well as several other parameters.

As it turned out, one of the remaining problems was that the vibrating tips in the injectors were so worn that most of them would not hold any pressure after the car was shut off – they continued to drip fuel until all pressure was released. My solution – short of replacing the injectors, was to put a jumper in the fuel relay under the dash and run the fuel pump until the pressure was built back up – you could hear the pump when it reached the point of re-establishing pressure. Then I put the relay back in and the car started immediately.

The problem I have with the Audi is that I can shut off the warm engine and immediately try to restart – and it will not. It will only turn over with no sign of ignition. If this was a bad accumulator or leaky injectors, it seems that it would restart immediately upon shut down. As it is, I can fairly accurately predict when the car will restart based upon ambient air temperature and having the hood open. It is as if a switch is turned on – one minute it will crank with no sign of ignition and then literally the next minute fire right up with no signs of fouling, flooding or any other problem.

Thanks again for the advice, if I ever figure it out I will post the solution.

[DoctorD15]

someone recently told me to try unplugging the cold start valve, because it could be going off everytime the cars started, so therefore the car would start great in the cold because its working properly, but making the car start poorly when warm, because its shooting off and almost flooding the engine and fouling up the start. I'm not too sure about this one, but at this point i'm willing to try anything, so you may want to give that test a try.

[Tripod]

OK, here is the solution. The part in question had to completely fail before it was detected by a fault code. The code 2-1-1-2 finally appeared after the car would not start. Looking this up in the service manual indicated a bad REFERENCE SENSOR. $170 later and about 10 minutes to replace the car now starts cold or hot with no other symptoms.