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stefano, Auto Service Technician
Category: Ford
Satisfied Customers: 437
Experience:  I have been an auto mechanic for 15 years, 12 years with Ford. ASE Master and Ford certified.
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fuel injectors not firing

Customer Question

I have a 91 F250 w/351. Fuel pressure is good on rail, but injectors don't appear to be firing, cause when I spray in ether, starts up just fine.
Submitted: 10 years ago.
Category: Ford
Expert:  stefano replied 10 years ago.
Hello. So you do have fuel pressure at the fuel rail? The Powertrain Control Module(PCM) has internal drivers that control the injectors. There is an orange ground wire that comes off the injector harness that grounds on the back of one of the cylinder heads. Check this ground and make sure it is ok. Also, a shortd O2 sensor can cause this problem. Un plug it and see if that makes a difference. Get back to me and then I will get back to you soon. If you need wiring diagrams I can send them.
Customer: replied 10 years ago.
I have to get going for right now, I will check when I get back, just to let you know though, this happened while I was away... The truck hadn't been driven in some months and when I came back to drive it, it just wouldn't start and then I started looking into why.
Customer: replied 10 years ago.
Sorry, just wanted to say one more thing before I took off... that may or may not be relevant. The fuel pump relay clicks erratically, I did replace it with a new one, and it does the same thing.
Expert:  stefano replied 10 years ago.
Hello. I am attaching 2 wiring diagrams. Check circuit 361, the primary side of the relay. This is what activates the relay and injectors. It is powered and grounded by the computer.graphicgraphic