Hi guys,

I have a 87 S4 Turbo2 FC
It has a kill switch custom wired to the fuel pump.
Anyway,

So, I ran into this really weird problem.
After I replaced a blown turbo with a used stock turbo I decided to start the car up and test the turbo a bit. The car started right up. Idles a bit low and then dies.

I tried again to start it, and give it a bit of gas on start, the car starts right up and I push the pedal to maintain the idle for a few sec, after that the car idles by itself at 1.1k

Then I turn off the car. Starts it for the third time after a hour. The car won't start. At first I thought it was the fuel pump switch (custom wired switch to kill off the fuel pump), so I turned the switch, the car has hard time starting, but eventually starts for 3 second and then died.

So I realized the fuel pump was on the whole time, and whenever the fuel pump is on, the car will not start, when the fuel pump switch is at off. The car will start after about 5 second of crank, then once it starts I turn the switch back on and the car starts to idle.

I'm pretty confused now about what could've caused this problem.

Any input is appreciated and can be a big help.

 

Thats why the switch is there so when it floods you turn it off then when it starts you flip it again to turn the pump back on.

 

Yeah, but what I would like to know is what could've caused the flood. It wasn't doing that just a hour ago. And I haven't change anything on the car when the problem occurred.

 

Was your engine still warm when it wouldnt start? Thats when the majority of flooding issues seem to present themselves.

 

Yeah, the engine was warm.

 

Usually if there's a fuel pump kill switch, it's because the injectors are known to leak. If the fuel pump was pressurizing the injectors with the engine off, and the injectors leak by, then you're filling the engine with fuel, washing away all the compression.

Inside the Airflow Meter is a switch that prevents the fuel pump from turning on when the engine is not spinning. As soon as you start cranking the car, the airflow meter flapper opens a little bit and the fuel pump starts.

If you don't want this to happen again, get your injectors cleaned and balanced by a professional. Or get new ones. Also, make sure you check the engine's compression. Flooding is only aggravated by low compression.