No power to fuel pump relay

Tiny
DEREK HARMON
  • MEMBER
  • 2003 CADILLAC CTS
  • 3.2L
  • V6
  • AUTOMATIC
  • 150,000 MILES
Hello, I have the car listed above and the original problem is sputter crank. I looked on YouTube and found a way to jump the starter relay. Did that then the security system kicked in. Now I have no crank at all and no power to the fuel pump. Tested the power to the fuel pump relay and get power constant to one port and turn the key to on but no power to the other port. Please help.
Sunday, March 29th, 2020 AT 10:11 AM

5 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good afternoon,

The load side is fed by the fuse I highlighted in the diagram. That has power all the time.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

The control side is sent by the ECM for 2 seconds with the key on. It returns when cranking.

Roy
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Sunday, March 29th, 2020 AT 10:46 AM
Tiny
DEREK HARMON
  • MEMBER
  • 3 POSTS
Roger. So with the no crank and no communication with the fuel pump is it safe to say that the eco needs replaced? Switched fuel pump relays to one that I know works and still the same problem.
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Sunday, March 29th, 2020 AT 11:16 AM
Tiny
ASEMASTER6371
  • MECHANIC
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No, not at all.

Did you verify voltage to the relay as I suggested?

You need power to the relay before it can pass power to the pump.

Roy
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Sunday, March 29th, 2020 AT 11:21 AM
Tiny
DEREK HARMON
  • MEMBER
  • 3 POSTS
There is constant power to the relay. There is no power on the return side when the key gets turned on.
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Sunday, March 29th, 2020 AT 5:10 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
The load side has constant voltage. When the control side powers the relay, it closes and sends power to the fuel pump.

The control side power comes from the ECM for only 2 seconds with the key on. It will be constant voltage while cranking.

Did you verify this?

Roy
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Sunday, March 29th, 2020 AT 5:17 PM

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