96 Jimmy fuel pump won't run in cold weather -relay clicks off

I have a 1996 Jimmy 4dr 4x4 4.3L Vortec. When the vehicle is in the cold (winter in Indiana) the vehicle will not start. The fuel pump in the gas tank will not run. The fuel pump relay kicks off. When we move the vehicle to a heated garage (for 24 hrs minimum) it will then start. The relay fuse has been replaced. Added a bottle of Heat to it and it started for a few days, but now it's back to not starting. Before going out and purchasing a fuel pump (esp. after reading forums) would like to hear any advice anyone has out there.
Thank you in advance.
1-96-Jimmy

Jumper fuel pump with a fused jumper.
And run a fuel pressure test on fuel pump.

Does the fuel pump relay kick off on engine cranking or engine running?

DOES IT HAVE THE 2 SECOND KEY ON fuel pump run/prime up?

What fuse was replaced?

Does it blow fuse or does relay just kick off on engine start or run.?

Have you switched relay for a known good one?

MT: Does the fuel pump relay kick off on engine cranking or engine running?
1-96-Jimmy: When you turn the key (after vehicle has been in a warm garage) you hear the fuel pump. When the vehicle is in the cold, you turn the key and you don't hear the fuel pump and then the relay kicks off.


MT: DOES IT HAVE THE 2 SECOND KEY ON fuel pump run/prime up?
1-96-Jimmy: Unknown

MT: What fuse was replaced?
1-96-Jimmy: To our knowledge, there is no fuse, just the relay.

MT: Does it blow fuse or does relay just kick off on engine start or run.?
1-96-Jimmy: See last response.

MT: Have you switched relay for a known good one?
1-96-Jimmy: Yes, relay has been switched with a known good one.

1-96-Jimmy: When this problem started (out of the blue) it was an exceptionally cold night and the car had been parked in a parking lot for several hours. First thoughts after unsuccessful jumps were ice in the fuel line or the fuel pump which wouldn't allow the pump to run.
We are aware that the fuel pump comes on and runs but if you don't start the vehicle right away, the pump builds up pressure and then turns off.
Led to think possible ice in the pump. Added Heat and towed vehicle to heated garage. Half a tank of gas later, it is repeating the problem of not starting in the cold.

Thank you for your quick response.
1-96-Jimmy

MT: Does the fuel pump relay kick off on engine cranking or engine running?
1-96-Jimmy: When you turn the key (after vehicle has been in a warm garage) you hear the fuel pump. When the vehicle is in the cold, you turn the key and you don't hear the fuel pump and then the relay kicks off.


MT: DOES IT HAVE THE 2 SECOND KEY ON fuel pump run/prime up?
1-96-Jimmy: Unknown

MT: What fuse was replaced?
1-96-Jimmy: To our knowledge, there is no fuse, just the relay.

MT: Does it blow fuse or does relay just kick off on engine start or run.?
1-96-Jimmy: See last response.

MT: Have you switched relay for a known good one?
1-96-Jimmy: Yes, relay has been switched with a known good one.

1-96-Jimmy: When this problem started (out of the blue) it was an exceptionally cold night and the car had been parked in a parking lot for several hours. First thoughts after unsuccessful jumps were ice in the fuel line or the fuel pump which wouldn't allow the pump to run.
We are aware that the fuel pump comes on and runs but if you don't start the vehicle right away, the pump builds up pressure and then turns off.
Led to think possible ice in the pump. Added Heat and towed vehicle to heated garage. Half a tank of gas later, it is repeating the problem of not starting in the cold.

Thank you for your quick response.
1-96-Jimmy


You are welcome.

Key on fuel pump should run for a 2 second prime up from relay on.

Engine cranking the fuel pump should run when cranking if it has spark.

Whe it is cold and fuel pump does not run jumper fuel pump {the gray wire} with a fused jumper and see if it will run.

Could be a weak connenction some place.