I'm trying to figure out my wiring diagram c/o Haynes (engine control system-2.8v6 MPFI). It seems to have two seperate circuits to supply power to the fuel pump. First a fused hot wire supplies power to a oil pressure switch which is open/engine off and closes/engine running. As the engine starts to run oil pressure closes the circuit and sends power to the fuel pump, right??. Ok so the second circuit, the fuel pump relay sends power to the fuel pump via the ECM, but it seems like it only powers up the fuel pump during priming. Is this how it works? does the ECM run the fuel pump only on start up and oil pressure switch takes over to supply power to the F/pump? Pete help!

Thanks for any replies

Mike

 

Looks like you got the idea. The ECM controls the pump prior to starting. When the key is ON the ECM closes the pump relay and the pump primes the FI system. If the ECM does not see the engine spinning within 3 seconds it shuts the pump off. Probably to avoid flooding. If the engine starts and the oil pressure rises above 5 PSI the switch in the oil pressure sensor closes and feeds power to the fuel pump. What is not clear, wether the fuel pump relay opens after the pressure switch closes or remains closed and both paths feed the pump. The best I can make out is that both paths remain active as long as the engine runs, probably to relieve some of the current through the pump relay contacts, maybe.

 

Thanks Pete, I think you're right on having both paths feeding during engine run. Looking at the Haynes wiring diagram shows that two leads connect the fuel pump relay to the ECM. One seems to ground the field and makes contact to supply power and an other with 12v. to help during priming in quessing. Sometimes I really wish I could afford the "Factory Repair Manuals" as they are much more detailed and easier to understand. Thanks again.

Mike

 

The Chiltons Total car care uses factory information. (#28282)

 

You can subscribe to All Data DIY for about $20 per year, just as much info as the FSM plus recalls & tech bulletins, only problem you need a computer to use it. http://www.alldatadiy.com/

 

The thing with the alldata is it will probly show the same things as the book less reaclls and technical notes. And you get to keep the book! I paid I think it was $24.95 for one year for the swap I am doing in my mom's S10. (I hope I finish it in a year) And being on dial up I want the darned page now! I get the same diagrams from alldata that I have in my book.

 

Go to Autozone. They are the onesthat own Alldata. Maybe if you tell a cashier he or he is cute they will print you a few pics.

 

Just a sample of what is in the book and what Alldata shows.

 

great info guys. Madmike, I couldn't really make out the pictures to well on my end but the info seems alot better than my Haynes. I'll check it out all this info really helps me alot.

 

Sorry. My knowledge of posting pics is very poor.[&o]