Fuel Pump electrical question-not working

Fuel Pump electrical question-not working

Postby mello000 [OP] » September 29th 2010, 10:44pm

1999Astro Van 2 wheel drive
My fuel pump in gas tank is not working-pumping
I checked two methods
Listing on stethoscope dropped in gas tank no fuel pump motor noise when key turned in on position
Removed gas filter ---tried to start no gas exiting open line

I replaced fuel pump relay under hood -no change
Checked wiring to fuel pump near gas tank
7 wires in plug in harness near tank that exit harnes and go to top of tank to fuel pump
Colors of wires are
1 purple wire W/ white stripe--approx 20 gauge wire
2 wires each black with white stripe-- approx 20 gauge wire
1 solid green -------------------------------apprx 20 gauge wire
1 Brown W black stripe-------------------approx 20 gauge wire

1 Solid Gray----------------------------approx 14 or 16 gauge wire
1 Solid Black---------------------------approx 14 or 16 gauge wire

I was told by a Chevy dealer 2 wires should have voltage
1 st------------ 5 volts
2nd wire-- 12 volts

I checked with multimeter and discovered the brown wire with black stripes has 5 volts
Checked other 6 wires and there is not 12 volt in any of these wires
The gray wire is heavy 14 to 16 gauge I assumed probably the 12 volt wire
as a method of checking fuel pump I jumped 12 volts to this heavy gray wire
Still fuel pump motor does not start ,pump always checked with ignition on


Does anyone know if the heavy gray wire is supposed to carry 12 volts to fuel pump?
If not which wire should carry 12 volts ?
Or is 5 volts OK

Any suggestions on what else I can do to find problem electrical?
Or is it likely fuel pump is bad?


Sincerely
Richard
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Re: Fuel Pump electrical question-not working

Postby Phantom » September 29th 2010, 11:09pm

I have a diagram can post , will take few , unless someone else has one handy, fuses checked?
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Re: Fuel Pump electrical question-not working

Postby RECox286 » September 29th 2010, 11:15pm

Whoa, Richard.

Back up a bit. If you have a '99, then there is a good chance you have more than 100k mi on the Odo. This is when you start to have the Chevy gremlins give you fuel pump problems. My bet is that you need to replace the pump (Ooooh, noooo, Mr. Bill) One thing you can try at this point in time is to get under the truck with a trusty hammer, yes you heard right, and smartly smack that old fuel tank, that is: make it vibrate. Sometimes, the pump will miraculously spring to life. If it does, do not trust it to continue to do so, because now, you will definetly know that you need to change the pump.

The PCM runs the fuel pump for 2 seconds, when you turn the key to RUN and then terminates 12v to the pump, unless the PCM "sees" the engine running, which is when the oil pressre switch takes over and runs the pump. Normally the electrical system works as advertised, and the pump itself is the weakest link in the fuel system, for sure.

Good luck, let us know how you are making out.

Bob
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Re: Fuel Pump electrical question-not working

Postby Phantom » September 29th 2010, 11:34pm

The gray wire goes from pump sender unit to the under hood fuse/relay center wich has fuel pump relay and out of the relay is an orange wire that goes to the ECM B fuse 20amp , black wire on relay is ground , the diagram is broken into 4 separate diagrams ,I figured it would be faster to tell you where they go , I will trace the other wires

Edit ; here is where the other wires at sending unit go

dark green/-white goes to vcm vehicle control module
purple/white- fuel level input at VCM
blk wire- of of sending unit goes to ,engine harness 6 cm from generator breakout toward rear of engine
Last edited by Phantom on September 30th 2010, 12:34am, edited 2 times in total.
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Re: Fuel Pump electrical question-not working

Postby Phantom » September 29th 2010, 11:47pm

It took nearly 15 minutes for that post to load , i will now trace the other wires , but the gray wire does feed the power , , if that 20 amp fuse is bad it will prevent power from reaching pump
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Re: Fuel Pump electrical question-not working

Postby mello000 [OP] » September 30th 2010, 1:16am

Thank you guys for taking time to reply to my inquiry

Based on your"great information "I am going out to Astro with flashlight, tester, and large hammer (Now Dark EST) to check
the possibilities and will reply again.
Sincerely
Richard
Original Poster [OP]
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Fueling (1/4 tank)
Fueling (1/4 tank)
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Re: Fuel Pump electrical question-not working

Postby mello000 [OP] » September 30th 2010, 2:11am

UPDATE

Checked ECM B 20 amp fuse--------- OK
I checked all fuses before in both fuse boxes inside firewall and under hood
and appeared all OK
But based on your reply's wanted to be sure and checked this fuse ECM B 20 amp again and it is perfect.
I also checked power to fuse ECM B 20 amp fuse box slot and yes one side has 12 volts
as it should have if OK .


Because of your reply---- I now know to check 12 volts on Gray wire near gas tank --- I need to be testing gray wire as key is turned
I now know I only have 2 seconds of voltage because my van never starts and oil gauge power supply will not transfer over supplying constant 12 volts
I am alone and had no one to turn key while I check voltage
I will do tomorrow -thank you for this valuable information
But as in reply's I am now about 99 % sure it is the pump.
Next update tomorrow
I again thank you all for help.

Sincerely
Richard
PS I did not hit tank with hammer now because neighbor sleeping
I will do with pleasure tomorrow--- take out a little frustration
Original Poster [OP]
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Fueling (1/4 tank)
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Re: Fuel Pump electrical question-not working

Postby Phantom » September 30th 2010, 2:34am

It does appear to be pump , they do go bad , if you have some wire laying around you can rig a test light to reach out to the side so you can turn and look as you turn the key and see if it lights up , any bulb that works on a few volts will work , using an old turn signal socket or tape wire to bulb,,,how did the hammer test go?
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Re: Fuel Pump electrical question-not working

Postby mello000 [OP] » September 30th 2010, 1:19pm

Thank you all again
Phantom
Now 8 AM EST and just came back from testing Astro wire -raining like hell but I am determined to fix today
I did exactly as you mentioned test light to Gray Wire near gas tank attached a long wire from gray wire near tank to inside of Van so I can see test light as I turn Key in ignition


"Gray wire" as I was told in earlier mail originates from
ECM-B 20 amp fuse block and carries 12 volts for 2 seconds
then after starting oil pressure hot continues 12 volts
Terrific information -Dealer I spoke to did not know this about temporary on of 12 volts and then transfer of 12 volts

"Confirmed fuel pump bad" as I have been told -----when key turned test light does go on for on for two seconds then off
Than you again


I will update again after installation of new fuel pump and I dry off

Sincerely
Richard
Original Poster [OP]
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Fueling (1/4 tank)
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Re: Fuel Pump electrical question-not working

Postby mello000 [OP] » September 30th 2010, 1:25pm

Phantom
I did not yet hit with hammer but I will
Because of help----- confirmed by tests----- I am positive it is the pump but
I still want to beat on tank to see if it temporarily frees fuel pump motor.

I will update

Sincerely
Richard
Original Poster [OP]
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Fueling (1/4 tank)
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Re: Fuel Pump electrical question-not working

Postby Phantom » September 30th 2010, 2:21pm

Good to hear to are making progress . , sometimes banging an old electric motor can vibrate the armature and help cause an electrical contact , but as suggested before don't think it fixed if it starts , cause it will fail again ,and it may be somewhere other than home. The hammer trick can also be used on starters and window motors and others . Hope install goes well
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Re: Fuel Pump electrical question-not working

Postby RECox286 » September 30th 2010, 10:55pm

Not only cars, but on various airplane parts as well. More than once I got things going with ye ol hammer trick, at least til we got home.

Bob
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Re: Fuel Pump electrical question-not working

Postby astroturf » October 1st 2010, 12:49am

No Place to pull over up there Bob...
My Cup is neither half empty nor half full... But has a hole in it. Holy Cup Holders Batman. LOLz, Jim
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Re: Fuel Pump electrical question-not working

Postby rev_les » October 1st 2010, 2:14am

astroturf wrote:No Place to pull over up there Bob...

lmao... "Fellas, I have good news and bad news....the good news is we will be landing immediately, the bad news is we're crash landing" :rofl:
Edit* to keep this on topic, be sure to get a new fuel filter along with the new pump :D
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Re: Fuel Pump electrical question-not working

Postby mello000 [OP] » October 1st 2010, 5:43pm

Update ON FUEL PUMP REPLACEMENT
I Have taken my fuel tank out of van
In doing so I disconnected the three lines that connect on the top of the fuel pump AND ON THE TWO METAL FUEL LINE AND ONE METAL VAPOR EXIT LINE
I disconnected these three lines not on the top of the fuel pump but where they connect to flared metal lines on Van
I HAVE PURCHASED A NEW FUEL PUMP( AC Delco AS RECOMMENDED IN REPLY'S ON SITE THANK YOU.
WHEN i DISCONNECTED THESE THREE LINES IT APPEARED ( I did this at night with not terrific lighting)
it appeared there was a plastic flair slide TYPE BUSHING on the metal fuel line after the flair ( something similar to a plumbing compression copper flair nut) accompanied with small rubber o ring type washer OR TWO l
I took off all three lines here and cannot find any o ring type washers or the plastic flair not good

Does anyone have any experience with this TO REPLACE FLAR BUSHING AND O RING TYPE WASHERS
or where I can purchase the three short (about 18 inches) plastic lines connecting fuel pump to the metal flared lines on the body of the van ?


Again I thank all for help
Sincerely
Wet Richard-- raining like hell here -----at least not snowing
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Re: Fuel Pump electrical question-not working

Postby astroturf » October 1st 2010, 9:44pm

Ditto to my other post.

http://www.gmpartsgiant.com/Page_Produc ... &ddlSm=2WD

Hope it helps, Jim
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Re: Fuel Pump electrical question-not working

Postby RECox286 » October 1st 2010, 10:10pm

I do most of my grazing at the local JY. Not all trucks end up there because of cancer or old age. The "HELP" display counter has also been a good source for odd parts.

Good luck, nice to see you are on the way to being fixed.

Bob
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Re: Fuel Pump electrical question-not working

Postby Phantom » October 1st 2010, 10:23pm

Assembly of the fuel pump and lines , with part numbers
http://www.gmpartsgiant.com/components/ ... 11006.html
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