LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Fuel Pump Wiring Question

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Old Aug 26, 2006 | 03:47 PM
  #1  
97silverTA's Avatar
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From: Amarillo,TX, Norman,OK
Fuel Pump Wiring Question

I've done a lot of searching and found good info, but I need some help.
First off, I'm not getting fuel pressure.
I tested the orange wire at the fuel pump relay, and it is hot. The ground to the fuel pump is good, However the green/white (pcm to relay I believe) wire is not hot when I turn the key on.
I know the pump is good b/c I jumped the orange wire to the gray wire and the pump worked.
My question is...... What is the problem if I'm not getting a signal from the green/white wire to the relay. I just did a opti install if this would cause any problems.
Old Aug 26, 2006 | 03:53 PM
  #2  
Kevin Blown 95 TA's Avatar
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Re: Fuel Pump Wiring Question

I seem to remember reading that the fuel pump might not run if the PCM doesn't see the right opti signals, so maybe start with the opti connector. Don't forget you can test the FP by providing 12V to the test jumper in the bundle of wires coming from the PCM on the pass side fender. It's tucked inside the split loom.

Last edited by Kevin Blown 95 TA; Aug 26, 2006 at 03:55 PM.
Old Aug 26, 2006 | 04:17 PM
  #3  
97silverTA's Avatar
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From: Amarillo,TX, Norman,OK
Re: Fuel Pump Wiring Question

I did test the FP and it is good. How do I test the signals from the opti?
Old Aug 26, 2006 | 05:58 PM
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Kevin Blown 95 TA's Avatar
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Re: Fuel Pump Wiring Question

Originally Posted by 97silverTA
I did test the FP and it is good. How do I test the signals from the opti?
I'm not sure how to tell you how to do that other than it might popup in a code that you are missing certain timing signals. I have access to a scope, so I would probably look at it that way if I couldn't find something obvious.
Old Aug 27, 2006 | 01:01 AM
  #5  
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Re: Fuel Pump Wiring Question

The ECM has a 2-3 second run time on "Key ignition" to prime for pressure on the green white wire, once that happens it waits till the cranking/motor run signal starts. Are you checking it with someone else tuning the key to the on position?
A chiltons manual will tell you what wires to check for hi res signal on the opti. I know it's a 3-5 Volt AC signal on the D wire and I think the B is the ground wire.
Also the fuel pump wire is the green white wire in the red connector to the ECM, wire #7
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