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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15201
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Kinda following a convo you had a while back and im trying

Customer Question

Kinda following a convo you had a while back and im trying to fix my 02 avalanche can you assist
Submitted: 1 year ago.
Category: Chevy
Customer: replied 1 year ago.
how long does it take to get a reply???
Customer: replied 1 year ago.
if this really takes over 40 mins to get a reply you aren't really helping me much....????
Expert:  Reggie Whiddon replied 1 year ago.

Hello I am reggie let me help you. IT does sound like you have a fuel problem and you say the gauge isnt working and it was, do you hear the fuel pump run?

Expert:  Reggie Whiddon replied 1 year ago.

Had you been having any performance issues at all with your truck? If you are not hearing the pump, access the fuel pump relay in the under hood box, do you have a voltmeter, test light>

Customer: replied 1 year ago.
when I turn the key to the on position I hear a click under the hood but nothing from the fuel tank
Customer: replied 1 year ago.
I do have a test light.... I have never had issues with this I ran out of gas bout 5 months ago and put fuel in and it started... this time it was at an angle and all the fuel was towards the back of the tank
Customer: replied 1 year ago.
I have volt meter but don't know how to use it.... I also have no pressure in the fuel rail now
Expert:  Reggie Whiddon replied 1 year ago.

well here is an easy one to try take a hammer and have someone try to crank it and while they are attempting to start you whack the bottom of the tank in the area were the pump is located it will start

Customer: replied 1 year ago.
What will this do??? What do u need test light for then
Expert:  Reggie Whiddon replied 1 year ago.

Okay when a fuel pump fails it is just like any other electric motor either the brushes or the communtator have a bad spot in them and when you take that hammer and hit it it will start working and if it does well we know for a fact you have a bad fuel pump

Expert:  Reggie Whiddon replied 1 year ago.

I went that route because you stated you didnt know how to use a voltmeter.

the hammer is how we get them started when they are towed in and we dont feel like pushing them in shop

Customer: replied 1 year ago.
I checked the ground and the hot wire in the fuse box for the fuel pump and I have a good ground and power.... I seen something about crossing a wire to one side and the other and try to turn key to on to see if I can hear the pump which would indicate a bad fuse but kinda confused on that....
if I turn the key to the on position should the pump kick on???
Expert:  Reggie Whiddon replied 1 year ago.

Okay here is what you can do, remove the fuel pump relay on the bottom of the relay are some numbers

85 86 87 30

take your test light and make sure you have voltage on either 30 or 87 at all times if you do put a jumper wire in between 30 and 87 that sends power directly to yoru pump

Expert:  Reggie Whiddon replied 1 year ago.

You cannot check the ground in the fuse box it is back by the tank on frame rail

Customer: replied 1 year ago.
ok so test light hooked to a ground check the 30 and 87 to see if I have power if so then run the jumper from 30 to 87 with key off or on???
Customer: replied 1 year ago.
Key off I have power in 87 nothing on 30 and when I jump 30 to 87 and turn key I get nothing from pump
Expert:  Reggie Whiddon replied 1 year ago.

Okay you did it right, with your jumper in place go back there and hit the bottom of the tank

Expert:  Reggie Whiddon replied 1 year ago.

okay im bout to go to lunch i will ck on you when i get back

Customer: replied 1 year ago.
Do I need key on of off
Customer: replied 1 year ago.
I tried the jumper and hitting tank and nothing
Expert:  Reggie Whiddon replied 1 year ago.

It doesnt matter about the key. Okay do you see the connector for the fuel pump

Customer: replied 1 year ago.
I see where the fuel pump is but no way to hit it so I've tapped the bottom of tank nothing...
Went thru all the fuses exam fuse was blown changed that out started right up 39 sec later it died... No pressure in fuel rail n won't start again
Expert:  Reggie Whiddon replied 1 year ago.

exactly what fuse was blown

Expert:  Reggie Whiddon replied 1 year ago.

the reason i ask is earlier you checked and you had power on the relay and you had not replaced a fuse then

Expert:  Reggie Whiddon replied 1 year ago.

when you say exam fuse do you mean the ecm fuse?

Customer: replied 1 year ago.
it's a small 20 amp I changed that out n it fired. But won't do anything now but turn over
Expert:  Reggie Whiddon replied 1 year ago.

And it is labeled ecm? okay let me look this up

Expert:  Reggie Whiddon replied 1 year ago.

sir very important here was it labeled ECMB

Expert:  Reggie Whiddon replied 1 year ago.

oR was it ecmi I think it would have been ecmi because that fuse also supplies power to fuel composition sensor its back under your truck i bet you hit it or cut a wire get under there and unplug it replace fuse and crank vehicle

Customer: replied 1 year ago.
Cut a wire where I didn't touch any wires... I'm not under the hood I went to buy a fuel pump while u had a ride.. The stuff to see telling me are resulting in nothing the fuel gauge wasn't working I checked FUSES under the hood there was a small 20 amp fuse rught above the big horn fuse it said exam something it was blown I changed it fuel gauge worked it started then died. I hit under the tank as u instructed the tank doesn't have any wires under it
Expert:  Reggie Whiddon replied 1 year ago.

I am not saying you cut them i meant that when you backed in the ditch there is a sensor under truck that is tied in on that fuse and if you hit it perhaps some damage and that may have been where the fuse was blowing

Expert:  Reggie Whiddon replied 1 year ago.

And following the steps that i gave you you found out that the relay had power you jumped that power eliminating a possible faulty relay, I know you are frustrated, but please understand i work with what i have you stated you didnt know how to read a voltmeter which is okay most dont therefore i put you through some test that didnt require use of one. The fuse you are describing powers up the ecm and the fuel composition sensor, which i might add i have seen several of them short out and blow that fuse

Expert:  Reggie Whiddon replied 1 year ago.

You getting a fuel pump is firing the parts cannon. Now if you want to fix this or at least get an idea what you have I am the man for the job i know every nut and bolt on that trucck and every wire color,, Hit me up and we will start over.

Customer: replied 1 year ago.
I'm not sure it's the pump but I can't hear it run n I have to pressure in the fuel rail so I'm assuming it is. The ditch wasn't that bad to hit anything under the truck so that can be ruled out I just don't know what else it could be.. I sorayed gas in the intake n it fired for a sec then nothing so I'm at a loss
Expert:  Reggie Whiddon replied 1 year ago.

Actually your making sense. Plus a fuel pump is a very common failure on your truck actually it's about all that goes bad. Are you going to put it in, it's not a bad job o can tell you some good shortcuts. And one thing when u buy pump insist on a Delphi pump

Expert:  Reggie Whiddon replied 1 year ago.

A good Delphi pump will set you back a couple hundred you got 2 straps, a filler neck and some evaporater hoses, I can wall you through it save you several hundred bucks

Customer: replied 1 year ago.
Yeah I got that pump cost me 300. I dropped the tank but to dark n cold to do any more tonight I'll have to work lil bit on it tomorrow night
Expert:  Reggie Whiddon replied 1 year ago.

Okay sounds like u got the good pump unless it's been changed before you will have to solder in a new connector, be sure the rubber seal for the pump is seated good. And once you got it in try n start it before u put the tank all thr way back up, incase we still have a problem. Another thing get a new fuel pump relay. Does yours have a fuel filter? If so change it. Something else that kinda bothers me u said thr fuel gauge didn't work was thst the only gauge inoperable? IL be looking to hear from u today

Customer: replied 1 year ago.
I dropped the tank put new fuel pump to the electric connectors turn key to on position n nothing from the pump... How do I check to see if I have power to the pump
Expert:  Reggie Whiddon replied 1 year ago.

Did you have to install a new connector? The gray wire is the power wire to the pump put your test light in between the black and gray wires and have someone try to start it

Expert:  Reggie Whiddon replied 1 year ago.

When you turn your key on does your check engine light up?

Expert:  Reggie Whiddon replied 1 year ago.

Also go back to the relay and jump 30 to 87 again ck for power on either 30 or 87

Expert:  Reggie Whiddon replied 1 year ago.

And dont worry you didnt waste any money on the pump if it wasnt bad it was just a matter of time