1995 Ford Probe GT, 150000 mi, 2.5L V6

KOHLBL

MEMBER
1995 FORD PROBE

At first my car was getting difficult to start. Eventually it stopped running altogether. I have replaced the spark plugs, fuel filter and fuel pump relay. The fuel pump inertia switch has been checked good as well as the fuel pump fuse. We used a repair manual to help in diagnosing the problem and they suggested jumpering at the diagnostic plug. We did jumper it and turned the key to the spot just before start. With the jumper in, the pump would run continuously. With the jumper out, the pump would not come on at all. Not even enough to prime the fuel lines. Again, with the jumper in, we get 12 volts at the pump terminals but absolutely nothing when the jumper is removed. What are we bypassing at the diagnostic port with a jumper? My understanding is that under normal circumstances, the pump should come on for a few seconds before the car starts and then shut off. It does not do that. What have I missed?

5 Replies

BLACKOP555

MECHANIC
10,371 POSTS

Check the fuel pump relay, that may be bad causing it not to send out a full 12v to pump.

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Friday, November 9th, 2007 AT 7:56 PM

KOHLBL

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3 POSTS

Thanks for the input. I actually did check the relay and although it checked good I put in a new one (kinda spendy!). The new relay did not have any affect on the problem. I also checked for power at the terminal connections for the relay. I get 12 volts at the connector.

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Friday, November 9th, 2007 AT 9:01 PM

BLACKOP555

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10,371 POSTS

Check for 12v at the fuel pump without the jumper if your not getting any checked for a cracked or cut wire.

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Saturday, November 10th, 2007 AT 7:02 AM

KOHLBL

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3 POSTS

That was strange. We have power at the fuel pump connector with the jumper but nothing without. We also checked the fuel level sensor (float) and it is sending a signal to the gage. What is being bypassed with the jumper? I figured what ever it is, it must be the culprit. I will look for some damage to the wires. Thanks.

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Saturday, November 10th, 2007 AT 9:41 AM

BLACKOP555

MECHANIC
10,371 POSTS

I woudl go from the ignition all under the hood, I have had a connector or two pop off in my day! It just might happen that the jumper bypasses the connector that may be loose or damaged.