pitzel Posted June 13, 2014 Report Share Posted June 13, 2014 Is it normal to be able to remove the fuel pump relay while the engine is running and have the engine continue to run? If removing the fuel pump relay = engine/fuel supply should die, and it doesn't -- where would a good place for me to start investigating? Oil pressure sender? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted June 13, 2014 Report Share Posted June 13, 2014 if you pull the relay, the only way the pump SHOULD be getting power is via the oil pressure switch. it doesn't rely upon the relay. the ECM control of the relay and the fuel pump priming connector both require the relay to be present for either of them to work though. sounds like the pressure switch is working as intended. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted June 13, 2014 Report Share Posted June 13, 2014 alternatively: if you pull the relay while the engine is running and it dies, you have a switch/wiring issue or REALLY low oil pressure. Quote Link to comment Share on other sites More sharing options...
tornado_735 Posted June 13, 2014 Report Share Posted June 13, 2014 Saar, I learn something new from you everyday, no lie. Thank you! Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted June 13, 2014 Report Share Posted June 13, 2014 Saar, I learn something new from you everyday, no lie. Thank you! then today you shall learn two things: GM by and large quit using the oil pressure switch as an alternative fuel pump power source in 1996. so, that trick is essentially OBD1 only. Quote Link to comment Share on other sites More sharing options...
pitzel Posted June 14, 2014 Author Report Share Posted June 14, 2014 (edited) then today you shall learn two things: GM by and large quit using the oil pressure switch as an alternative fuel pump power source in 1996. so, that trick is essentially OBD1 only. Did they do this because they had the airbags and other protection schemes available in the OBD2 ECU's? As I wrote in the other thread, I'm pretty sure the system is in place to meet a post-accident (or ruptured fuel line) fuel pump inhibition requirement. One of my older cars from the 1960s, with an electric fuel pump, if a line breaks or I get into an accident, will gladly pump the whole tank worth of fuel into the ensuing fire. Turning something that may very well have been mere body-work on the vehicle, into catastrophic damage. Edited June 14, 2014 by pitzel Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted June 14, 2014 Report Share Posted June 14, 2014 not likely. i find it more plausible that they dropped it due to it being unnecessary..... fuel pump relays don't fail all that often. Quote Link to comment Share on other sites More sharing options...
Taylor Posted June 14, 2014 Report Share Posted June 14, 2014 It was my understanding that the oil pressure sensor being connected to the fuel pump was to disengage the pump and shut the engine off in the event of the car rolling over. Quote Link to comment Share on other sites More sharing options...
Schurkey Posted June 14, 2014 Report Share Posted June 14, 2014 The oil pressure switch can keep the pump running if the relay fails. The oil pressure switch can NOT turn the pump OFF if the relay is still engaged. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted June 14, 2014 Report Share Posted June 14, 2014 ^ that. the only thing that will really prevent fuel pump operation is bad wiring, faulty PCM, a dead pump or a blown fuse. Quote Link to comment Share on other sites More sharing options...
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