[Gmecm] Re: Undignified death of a project :P

[Andrew Gibson]

Since this is the GM-ECM area I will add some info I hope everyone will find useful. You can challenge me on it if you want but having been a diagnostic tech for 10 years, I know. If you still don't think I know anything check www.nadiauto.com , yes that's my new ride.
   
  Low oil shutdown on GM products: Been there for years. Yes I had it on the truck. It works by the ECM powering a fuel pump relay on initial key on and cranking. Then the oil pressure switch takes over. The switch may directly power the pump or drive the fuel pump relay. Either way you have to have below 7 psi oil pressure for the amount of time it takes for the engine to burn off the residual fuel pressure. Works good if you flip the car upside down. Doesn't work so well to save the engine. :(
   
  Bypassing the Jeep fuel pump drive strategy: Jeep and all Chrysler products do not use a low oil pressure shut down. They use an Automatic Shut Down relay (I like automatic self destruct myself) which powers the fuel pump, ign coil, and injectors. The ECM turns the ASD relay on after it sees the cam and crank signals and properly indexes the engine for timing. After the indexing it commands the relay on so you still get a delay in building fuel pressure. Which is why a Chrysler product has to turn two full revolutions before starting when a GM only has to rotate 1/4 turn. I'll keep my GMC truck.

       
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