fuel pump relay location

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.

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.

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

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?

It's only supposed to power for 2 seconds and shut off until it sees a tach signal from cranking.

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.

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.

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.

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?

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.

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

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.

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

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.

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.

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.

Thanks nick 275 and JDL ,still working on it,replaced or made new ground.

Let us know what you find.

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

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?

Please respond to this here.

Why did you change the pump? Did it fail or was the fuel pressure low? New fuel pumps normaly do not fail so soon. If they do there is usually some other cause other than the fuel pump.
Try this. Remove the fuel pump relay and look at the terminal numbers printed on the relay itself. Jump out the terminal numbers 85 and 86 with a small wire on the fuse block where the relay plugs into. This will directly apply voltage to the fuel pump--bypassing everything else. If the pump does not turn on then check the ground for the fuel pump. Make sure it is a good connection. Also, make sure the connections on the new connector didn't come apart--especialy the ground..
A dirty gas tank can clogg a fuel filter in no time and cause the pump to over heat and it will eventualy fail. This is the most common cause of new fuel pump failures.

Also, the oil pressure sending unit will shut off the fuel pump if the oil pressure is too low or if it fails.

[quote:c7cab71545="pear69"]Please respond to this here.

Why did you change the pump? Did it fail or was the fuel pressure low? New fuel pumps normaly do not fail so soon. If they do there is usually some other cause other than the fuel pump.
Try this. Remove the fuel pump relay and look at the terminal numbers printed on the relay itself. Jump out the terminal numbers 85 and 86 with a small wire on the fuse block where the relay plugs into. This will directly apply voltage to the fuel pump--bypassing everything else. If the pump does not turn on then check the ground for the fuel pump. Make sure it is a good connection. Also, make sure the connections on the new connector didn't come apart--especialy the ground..
A dirty gas tank can clogg a fuel filter in no time and cause the pump to over heat and it will eventualy fail. This is the most common cause of new fuel pump failures.[/quote:c7cab71545]

The old pump stopped. But, it didn't stop instantly like this one. I started having to start it about three times. Finally it wouldn't start at all. I was told I would hear a humm when I turned the key just to the on position. I wasn't hearing it. So, I changed the pump and it ran great and I did notice the hmm after that. Yes I changed the pigtail like it said. I only had 1/4 tank when I changed the pump and dumped it. Wiped inside as best I could. There wasn't anything except specks of crud and not much of that. Just a few particles. This new pump was running great although I had someone tell me it should start the first time everytime. It didn't but the temps here have been in the teens to low 30's. It always started the second time. But yesterday it just wouldn't start at all.

[quote:9d3943b3f5="Don1188"][quote:9d3943b3f5="pear69"]Please respond to this here.

Why did you change the pump? Did it fail or was the fuel pressure low? New fuel pumps normaly do not fail so soon. If they do there is usually some other cause other than the fuel pump.
Try this. Remove the fuel pump relay and look at the terminal numbers printed on the relay itself. Jump out the terminal numbers 85 and 86 with a small wire on the fuse block where the relay plugs into. This will directly apply voltage to the fuel pump--bypassing everything else. If the pump does not turn on then check the ground for the fuel pump. Make sure it is a good connection. Also, make sure the connections on the new connector didn't come apart--especialy the ground..
A dirty gas tank can clogg a fuel filter in no time and cause the pump to over heat and it will eventualy fail. This is the most common cause of new fuel pump failures.[/quote:9d3943b3f5]

The old pump stopped. But, it didn't stop instantly like this one. I started having to start it about three times. Finally it wouldn't start at all. I was told I would hear a humm when I turned the key just to the on position. I wasn't hearing it. So, I changed the pump and it ran great and I did notice the hmm after that. Yes I changed the pigtail like it said. I only had 1/4 tank when I changed the pump and dumped it. Wiped inside as best I could. There wasn't anything except specks of crud and not much of that. Just a few particles. This new pump was running great although I had someone tell me it should start the first time everytime. It didn't but the temps here have been in the teens to low 30's. It always started the second time. But yesterday it just wouldn't start at all.[/quote:9d3943b3f5]

Ok I just jumped out the terminal numbers 85 and 86 with a small wire on the fuse block where the relay plugs into. There was nothing. Now I will drop the tank a bit to get to all the connections for the pump and look to make sure nothing came apart and check the ground.

I hope you get this before you drop the tank.
First check the ground wire for the fuel pump. The ground should be the black wire. It goes from the fuel pump (connector) and terminates either just before the gas tank,to the frame crossmember -or-to the frame somewhere after the gas tank. The ground on these systems (for some dumb reason) is connected to the frame, close to the gas tank, and it is exposed to serious corrosion. It should be accessable without removeing or dropping the tank.
Follow the wire harness along the inside of the frame rail just before the gas tank. The ground will jump out of the wire loom somewhere and terminate to the frame.

[quote:0d9c80b3f2="pear69"]I hope you get this before you drop the tank.
First check the ground wire for the fuel pump. The ground should be the black wire. It goes from the fuel pump (connector) and terminates either just before the gas tank,to the frame crossmember -or-to the frame somewhere after the gas tank. The ground on these systems (for some dumb reason) is connected to the frame, close to the gas tank, and it is exposed to serious corrosion. It should be accessable without removeing or dropping the tank.
Follow the wire harness along the inside of the frame rail just before the gas tank. The ground will jump out of the wire loom somewhere and terminate to the frame.[/quote:0d9c80b3f2]


Ok I do not have a tester anymore. Seems the kids messed that up. And I am aways from a store. I was wondering if the pump assy and gas float and sending unit are all in one and the connections are on top of the pump and I get a good gauge reading when I turn the key. Would that mean I am getting power to the pump and all?

The fuel pump power and the sending unit power are two different circuits and run at two different voltages, however they are in the same connector at the fuel pump assembly. The sending unit (I'm sorry to say) has nothing to do with the pump and has no ground reference. Did you find the ground? BTW--DO NOT stick the prongs of an electrical tester inside of the connectors without the proper lead prongs. The lead prongs I mean are very narrow and not the usual leads. Doing so will spread open the receptical of the connection and cause big problems...

Looking straight into the connector--what is the shape of it? Is it a square or like a flat rectangle? It has 4 wires--right?

[quote:c4a976926a="pear69"]Looking straight into the connector--what is the shape of it? Is it a square or like a flat rectangle? It has 4 wires--right?[/quote:c4a976926a]

I found the ground and it is connected. The pins are a flat rectangle. I am going to take the tape off just to make sure it didn't come apart in there. I have checked every fuse that I have also. May have been a waste of time but why not. It is looking more and more like the pump.

Clean the ground up real good, take it off and sand the connection with some sand paper or something. Jump out terminals 85 and 86 again just to see what happens. The ground can corrode behind the termination point--not visible.
The more things you can check as good the better so don't think anything you check is a waste of time--hang in there.
If it turns out to be the pump, then there is something restricting the fuel flow and causing the pump to work harder than it should. Make sure the fuel filter is new and installed correctly--the filter is directional. When the pump is working check the fuel pressure.

If you can run a wire directly off the battery and temporarily hook it up to the gray wire at the pump connector (where you spliced the new connector in)--the gray wire is the pump 12 volt feed wire. see if the pump runs. An electrical test would be better but I don't want to get the kids in more trouble.lol

[quote:a70bb895d5="pear69"]Clean the ground up real good, take it off and sand the connection with some sand paper or something. Jump out terminals 85 and 86 again just to see what happens. The ground can corrode behind the termination point--not visible.
The more things you can check as good the better so don't think anything you check is a waste of time--hang in there.
If it turns out to be the pump, then there is something restricting the fuel flow and causing the pump to work harder than it should. Make sure the fuel filter is new and installed correctly--the filter is directional. When the pump is working check the fuel pressure.

If you can run a wire directly off the battery and temporarily hook it up to the gray wire at the pump connector (where you spliced the new connector in)--the gray wire is the pump 12 volt feed wire. see if the pump runs. An electrical test would be better but I don't want to get the kids in more trouble.lol[/quote:a70bb895d5]

I AM IMPRESSED!!! I took the ground off. It was ok but...there was road grime and crud under it on the frame and some rust. I cleaned it off and sanded down the frame where it connects. Reconnected it and as I walked by the door I just had to see. I put my key in and tuned it to on. The pump kicked on. Oh and then it started the first time. I mean I didn't have to cycle the key to prime it. After seeing that mess I climbed under and cleaned every ground I could find. That should save me trouble in other areas as well. And yes most of the grounds were all the same with grime, rust and crud. After doing all of them I started it again. FIRST TIME START AGAIN! It runs great now. I can actually feel a differance in power. The pump must not have been working right from the start because of a bad ground. I was afraid to jump out terminals 85 and 86 after it started right up. Because I don't know if it would cause harm now that it is working right. LOL

I do want to thank you very much. And I will donate on the 15th when I get paid. It was well worth it.

Thank you,
Don

No need to jump out 85 and 86--those terminals just send direct power to the pump--it's a way to test the hot 12 volt wire to the pump.
There is really nothing that can 100% protect the ground from corroding again, but you can get-what they call--battery terminal protector. It is a red spray found at any auto parts store--I think CRC makes it. Spray it on the ground connection just as an added corrosion protectant to the bare metal that is now exposed.
Electric fuel pumps either work or they don't. If they turn on and off intermittently, the pump is usually not the problem..Congradulations on fixing this problem YOURSELF!

BTW--You thought you were on a wild goose chase--didn't ya-- :)

[quote:2e3123fea4="pear69"]No need to jump out 85 and 86--those terminals just send direct power to the pump--it's a way to test the hot 12 volt wire to the pump.
There is really nothing that can 100% protect the ground from corroding again, but you can get-what they call--battery terminal protector. It is a red spray found at any auto parts store--I think CRC makes it. Spray it on the ground connection just as an added corrosion protectant to the bare metal that is now exposed.
Electric fuel pumps either work or they don't. If they turn on and off intermittently, the pump is usually not the problem..Congradulations on fixing this problem YOURSELF!

BTW--You thought you were on a wild goose chase--didn't ya-- :)[/quote:2e3123fea4]


I admit I was getting worried. The company I purchased the new one from 5 months ago couldn’t find it in the computer. That would have been another $356.00 to do it again myself. And I will tell you that I am sorry it took me so long to follow your instructions. I am a disabled Marine and a single father raising a 7 year old boy. It would have been months before I had the extra money to buy a new one. My hat is off to you and you deserve a pat on the back. I got up this morning and it was 25 outside. It started right up. I will defiantly donate this payday. It was well worth it.

Thanks again,
Don Stuart