Bosch L-Jetronic on 1989 Spider

I'm nearing my Spider engine rebuild, and before trying to start the car, I wish to get rid of the 3 year old fuel. I thought that by leaving off the fuel supply pipe from the injection rail and switching on the ignition, the pump would operate and pump my old petrol out to enable me to put fresh petrol in. However, neither the auxilary or the main pump will operate. The reading on my meter at the pump wiring is 0V. Anyone know why? It seems to switch briefly, for about a second, and then stop again, and I can only tell this from a flash of a test lamp, since it is too brief to measure on the meter.

System is Bosch L-Jetronic. US specification car. All seemed to be ok prior to the engine rebuild (which is not in any way connected to this)

Is it something to do with the ECU?

3/9/07 - Problem solved. I primed the system by repeatedly turning on the ignition. I then felt rather bold and spun the engine..... and it started! Once started, the coil provides an input to the ECU to give an engine running signal, and this keeps the pump going.

Bit late with this response but that is exactly how the system is supposed to work. The pumps will operate when;

A) the key is first turned on (but run only momentarily just to pressurize the system)
B) the engine is cranking
C) the engine is running

This is a designed in safety feature to prevent fuel from being pumped out a ruptured fuel line in the event of a crash (assuming that the engine stops running, of course ).

Glad its sorted, another (late) tip is to take off the air filter and hold open the AFM flap this will turn on the fuel pump...

Originally Posted by fluffy

...hold open the AFM flap this will turn on the fuel pump...

On a GTV6, yes. Opening the AFM will turn on the fuelpump. But on a Spider, no; the AFM has no effect on the fuelpump. Same basic system achieving the same result in different ways. One is controlled by airflow and the other by ignition pulses. At least on US version L-Jets.