98 Gt Fuel Pump Question

[clean1998gt]

Hi im new to this thread. Ive heard a lot of good things about this forum. I have a 98 mustang gt 4.6L. It will not start. it cranks but wont turn over. i dont hear the Fuel pump turning on. all fuses look are good. i tested volts at IFS switch and im getting 12v. Would that indicate that my CCRM is good. Also when it test Volts on harness next to gas tank under the bumper im getting 7v there is that good.

 

[wmburns]

The 98 model year uses a two speed fuel pump with a ballast resister and speed control relay to change between high and low speeds. For the 98 model year it would be normal to see less than 12 volts at the IFS switch IF the fuel pump speed relay is in low speed mode.

IF you are testing key on 12 volts at the trunk IFS switch THEN that does mean that the CCRM is likely good.

Note. For the 98 and older Mustangs there aren't any active components between the IFS switch and the fuel pump. So if seeing 12 volts at the IFS switch and less at the fuel pump harness, this means:

• The IFS switch maybe bad
• There is a weak electrical connection in the wiring harness.
• the fuel pump ground is bad/weak.
• at the time the reading was taken the fuel pump was in the low speed mode. If true then 7 volts would be a reasonable reading.

If you never hear the fuel pump at run at initial key on AND the IFS switch has voltage, THEN the odds favor a bad fuel pump.

 

[clean1998gt]

The 98 model year uses a two speed fuel pump with a ballast resister and speed control relay to change between high and low speeds. For the 98 model year it would be normal to see less than 12 volts at the IFS switch IF the fuel pump speed relay is in low speed mode.

IF you are testing key on 12 volts at the trunk IFS switch THEN that does mean that the CCRM is likely good.

Note. For the 98 and older Mustangs there aren't any active components between the IFS switch and the fuel pump. So if seeing 12 volts at the IFS switch and less at the fuel pump harness, this means:

• The IFS switch maybe bad
• There is a weak electrical connection in the wiring harness.
• the fuel pump ground is bad/weak.
• at the time the reading was taken the fuel pump was in the low speed mode. If true then 7 volts would be a reasonable reading.

If you never hear the fuel pump at run at initial key on AND the IFS switch has voltage, THEN the odds favor a bad fuel pump.

Thanks for the info and quick reply. I don't hear the fuel pump turn on at all. It might seem weird but when I get in my car I never just fire it right up. I turn the key on the in position and let it beep and once it's done I fire it up I would always here the fuel pump. The car has 155k on it so I was guessing fuel pump. Just the Volt reading threw me off because of 12v at IFS and 7v at harness behind bumper . I plan on dropping the tank this week.

 

[jeno_labanca]

Thanks for the info and quick reply. I don't hear the fuel pump turn on at all. It might seem weird but when I get in my car I never just fire it right up. I turn the key on the in position and let it beep and once it's done I fire it up I would always here the fuel pump. The car has 155k on it so I was guessing fuel pump. Just the Volt reading threw me off because of 12v at IFS and 7v at harness behind bumper . I plan on dropping the tank this week.

Sounds like the pump took a dump

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