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post #1 of (permalink) Old 06-12-2000, 03:34 PM
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Fuel pump relay wiring?

I'm running a speed/density 5.0 HO in my '84 Toyota 4x. When I wired the fuel system into the harness, the diagrams I had weren't clear for the fuel pump relay. So I left the computer out of the circuit and ran the relay from a key operated circuit. It works fine, but the pump won't shut off when engine off and pump on, it bypasses. The engine is out of an '87 Mustang, the pump is a Carter 25% over stock replacement, and the lines are 3/8" feed and return. I'm pretty sure that the speed density computers are all basically the same. What in the Ford system shuts the pump off when pressure is up. Also, does anyone know where I can source an accurate diagram of this. I originally thought that the pump had an internal switch, but this is the second(of 2 pumps)that doesn't. The fuel pressure is on the money for application. The diagram I had was out of the Haynes (Mustang) book, and the circuit from the relay went everywhere other then to the fuel pump.
Thanks PJL
P.S. I'm here because it's all Ford running gear, tranny and t-case are late Bronco, and the axles are early Bronco.

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post #2 of (permalink) Old 06-13-2000, 02:36 AM
 
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Re: Fuel pump relay wiring?

Sorry can't help with the fuel pump relay, but your truck sounds sweet!!!

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post #3 of (permalink) Old 06-13-2000, 12:48 PM
 
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Re: Fuel pump relay wiring?

The Ford Fuel Injected Engines feauture a pair of Relays (at least my 88 351 does). I had to dig into the wiring when I had a no-start condition. When the ignition is turned to "Run" a signal is sent to the EEC Relay, which then causes power to be sent to the EEC Module. The EEC Module sends out a signal to energize the Fuel Pump Relay. The EEC sends a power on signal to the Fuel Pump Relay for about 2 seconds every time the key is turned to the Run Position. This serves to "Prime" the system, ensuring that there is enough pressure to start the engine. Once the engine is running, the EEC again sends power to the Fuel Pump Relay. I believe that the Fuel Pumps run continously as long as the engine is running. As soon as the engine is shut off or stalls, the Fuel Pumps are shut off by the EEC. As far as the inertia switch goes, it's just a safety switch that opens during a crash. It effectively opens the circuit and shuts off the pumps. Good luck.

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post #4 of (permalink) Old 06-14-2000, 02:38 AM
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Re: Fuel pump relay wiring?

Hey this is the answer I was looking for...but would you by chance be able to tell me what the number is on the in and out ports in the computer plug. Also what are the color codings on the relative wires that activate the relays. This would definitly clear up the confusion from the Haynes wiring diagram. I can see some excellent info to work from here.
Thanks again PJL
P.S. I left out the inertia switch to avoid 4 wheeling related circuit failures

post #5 of (permalink) Old 06-14-2000, 10:09 AM
 
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Re: Fuel pump relay wiring?

Hey Man: I can get the info when I get around to finding my book. If you are really curious about Ford Electronic Fuel Injection, I would recommend that you get this book from Amazon.com. It really does a good job of explaining how the entire system works. It's written by a retired Ford Engineer.

http://images.amazon.com/images/P/08...1.LZZZZZZZ.gif

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post #6 of (permalink) Old 06-15-2000, 12:35 AM
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Re: Fuel pump relay wiring?

Actually I used that book to understand my system and to troubleshoot, it's a great book. It's my buddy's, and the only problem I've found is that it's MAF oriented. I guess I could have ordered his older book, but found enough info to solve most of my bugs. This weekend I'll get in there and find the circuit that energizes for the couple seconds, then which powers up again while running. I'll look more closely through the Probst book I've got and try find the circuit. The fact that you pointed out the momentary energizing really gets me going on the right track. I'll post back if successfull, or not...
PJL

post #7 of (permalink) Old 06-15-2000, 09:26 AM
 
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Re: Fuel pump relay wiring?

There are schematics in the back of the book. Look for the wire that runs from the Computer to the Fuel Pump Relay. Good Luck.

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