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Fuel pump relay location

Tiny
MOODY69
  • MEMBER
  • 2003 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 56,000 MILES
Is there any sites where they go in depth on showing videos or pics. Where my fuel pump relay is located and troubleshooting my pump that just wont pump.I am trying everything first before dropping the tank which is full of gas
Sunday, May 2nd, 2010 AT 12:18 PM

33 Replies

Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
Fuel pump relay is in the underhood fuse block (on top of left front inner wheel well). if the fuel pump is not coming on, test the fuse, fuel pump relay and wiring to the pump. if all is OK, supply direct 12v power to the pump, if it comes on then must have wiring issue somewhere. if it doesn't come on then pump needs replaced. HEre is guide to help test the relay and the location int hediagrams below.

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

Check out the diagrams (Below). Please let us know what you find.
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Sunday, May 2nd, 2010 AT 3:55 PM
Tiny
CHARLES VAN B
  • MEMBER
  • 5 POSTS
  • 2003 CHEVROLET BLAZER
  • V6
  • 2WD
  • AUTOMATIC
  • 300,000 MILES
My vehicle listed above will not start the engine.
The starter does crank, but that's all.

Before I remove the gas tank to access the fuel pump, I am tracing back from the symptom to the ignition-switch.
Where is the fuel pump relay and should I suspect this component before I (again) drop the gas tank to access the fuel pump?
Thanks for re's. With images.
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Saturday, January 30th, 2021 AT 8:13 AM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good evening,

I attached a wiring diagram for you to view.

The relay is in the under hood fuse block and you need to remove it and test for voltages.

You need a constant 12 volts that is fuse controlled as in the diagram. Then the green/white wire is from the ECM for 2 seconds with the key on. It will have full power cranking.

The gray wire is the wire to the pump.

Roy

CIRCUIT DESCRIPTION
The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within two seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit
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Saturday, January 30th, 2021 AT 8:14 AM (Merged)
Tiny
RICHARDWEBB1978
  • MEMBER
  • 3 POSTS
  • 2002 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 220,000 MILES
I have a 2002 Chevy Blazer last night me and a buddy changed my fuel pump and we also checked the voltage at the harness and it was getting power. But you can hear the fuel pump relay clicking and after it clicks the power at the wiring harness is lost. What could be causing this?
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,762 POSTS
It's only supposed to power for 2 seconds and shut off until it sees a tach signal from cranking.
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
RICHARDWEBB1978
  • MEMBER
  • 3 POSTS
Well heres the thing before we checked the power at the harness it would only pump up to 25 lbs and then the relay clicked and all the pressure in the line dropped.
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,762 POSTS
The relay is working properly. If the pressure is immediately dropping off, that's another issue. That could be a bad check valve in the fuel pump.
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
RICHARDWEBB1978
  • MEMBER
  • 3 POSTS
The pressure check was before we changed the fuel pump we haven't checked the new pump yet cause we didn't know that the relay was suppose to do this. But we will check the new pump then.I let you know.
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
KEITHBH
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  • 1 POST
  • 2002 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 136,000 MILES
I shut my truck off, and when I went back out to start it 30 mins later it would crank over good, but it would not fire. I have checked for fuel and I am not getting fuel. You can not hear the fuel pump kick on at all. I have checked all fuses and relays. All good. I checked for power to the relay and it is good. What do I do next to find out if the problem is my fuel pump or something else?
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
JETSA
  • MEMBER
  • 117 POSTS
A sure fire check is unplug the fuel sending unit on top of the tank and take a test light clipped to a good ground. Put the pointer of the test light on the gray wire terminal and have someone turn the key to the run position. If the test light lights for approximately 3 seconds then you are getting the necessary voltage to the pump. There is also a ground wire in that connector that needs to be checked to make sure the pump is getting a good ground. That wire should be black, or black with a white tracer. If you have power and ground, chances are very good the pump is inoperative.
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
MATTHEW007
  • MEMBER
  • 1 POST
  • 2001 CHEVROLET BLAZER
  • 130,000 MILES
Fuel pump has power but when 12 volts at harness is put under load from fuel pump it drops to 3volts and wont turn on.

New fuel pump. Bench tested with 12 volts works good. Harness at fuel pump shows 12 volts when ignition is turned on but when connected to fuel pump the 12 volts drops to 3 volts. Checked larger ground wire connected to good ground on body of car just to check ground was not the issue, but still 3volts under load.

Checked relay in fuse block good. Fuse next to relay good.

I'm stumped to the drop in voltage.

Thanks for your help
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,869 POSTS
There's resistance in the 12 volt feed wire. That MIGHT show up with a test light but not with a voltmeter. Look for a corroded connection or splice. Possible bad fuel pump relay.
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
JOYFIXER
  • MEMBER
  • 9 POSTS
  • 2001 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 204,000 MILES
Why can't get any power to my fuel pump?I have changed the relay an checked all that I can.I I get power to the fuse block, but no power from there to fuel pump. Please help. Thanks joyfixer
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
You have to check wiring circuits at relay. Note diagram. Can you hear the pump turn on, key on engine off? At the fuel pump, engine cranking, gray wire is voltage, solid black wire is ground.
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
NICKB275
  • MEMBER
  • 24 POSTS
Ground wires were notorious for these models at the frame rail near rear bumper. Make sure the ground is against good clean metal. Get under the car and follow the harness coming from fuel pump and follow the ground wire indicated by JDL, this will hit frame at some point, you really want the best ground from tank to chassis, I have seen many GM pumps changed for ground reasons, also many pump fried due to bad ground and burnt pump.
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
NICKB275
  • MEMBER
  • 24 POSTS
Figure 6 is fuel pump ground conection # C402. Look at the #6 in figure on the frame. This is a ground which usually causes problems. Not saying this is 100% your problem, but should not be overlooked.
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
JOYFIXER
  • MEMBER
  • 9 POSTS
Thanks nick 275 and JDL, still working on it, replaced or made new ground.
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Let us know what you find.
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Saturday, January 30th, 2021 AT 8:16 AM (Merged)
Tiny
DON1188
  • MEMBER
  • 16 POSTS
  • 2000 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 130,000 MILES
I replaced my fuel pump 5 months ago. Today it started fine I drove it two blocks to the store. I came out and I won't start. There is no start up noise from the fuel pump like normal. I looked in the owners manuel and tried switching the grey relay. Looked at the fuze and it seems ok. There is no fuel coming from the tank. Is there a shut off somewhere? Something I don't know about? Could a pump go bad in just a few months? Any ideas?

Thanks
Don
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Saturday, January 30th, 2021 AT 8:19 AM (Merged)
Tiny
PEAR69
  • MECHANIC
  • 1,482 POSTS
Did you change the chassy wiring harness fuel pump connector when you changed the fuel pump? (Like your supposed to do)
Why did you change the fuel pump?
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Saturday, January 30th, 2021 AT 8:19 AM (Merged)

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