Consequences of a missing G4 Crank Position Pin

[UrS4boy]

The "patient" was an UrS4 with an AAN. It had been running fine but stopped while running and would not restart. The owner said that he had fuel at the fuel rail but no spark. With some suggestions from the forum and his own initiative, the owner checked switched coil power at the firewall connector rack (yes) and grounds for the coils and POSs (all good). He also used a G40 Cam Position Sensor LED tester (like Paul N's but from Marc S of EFI_Express) and found it was fine. We started to pull out our hair because nothing made sense. Finally, we suggested that he check to see if he still had a crank position pin (I provided this link: http://forums.quattroworld.com/s4s6/msgs/51259.phtml which is based on info from this forum (Thanks)). The UrS4 owner was busy on the weekend but finally got a chance to remove the starter and check for the pin today. This is the result (no pin):



Oops.

To me this confirms that the ECU *will* indeed trigger the J17 fuel pump relay based on just two things: a good G40 cam position (Hall) sensor signal and a good G28 engine speed sender (>23 RPM) signal, G4 Crank Position Sender be d@mned. Of course, without the G4, the ECU isn't confident enough to signal the POSs to spark the coils so the engine does not start.

The solution will be to make a pin and weld it through the starter hole

[S2central.net]

Interesting. But I am sure I have said before that ecu only activates FPRy when rpm exceeds ~25rpm. Good to have the logic confirmed ... Maybe there was an unanswered question about G4 being factored into that but it would certainly be easier for ecu to make that decision on rpm alone.

[UrS4boy]

Interesting. But I am sure I have said before that ecu only activates FPRy when rpm exceeds ~25rpm. Good to have the logic confirmed ... Maybe there was an unanswered question about G4 being factored into that but it would certainly be easier for ecu to make that decision on rpm alone.

I think the last time we had this "discussion" you suggested that all three signals (G4, G28 and G40) were required before the ECU would fire the J17 Fuel Pump Relay. This appears to be true. I *think* only once the engine is started, both the G4 and G40can drop out of the equation (fail) and the ECU will keep the engine going by continuing to count flywheel ring gear teeth and relate that to were TDC on No. 1 is and, therefore, continue to fire the injectors and the coils at the right time/duration.

No?