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Old 06-30-2011, 12:03 PM   #1
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Default 94 GMC K1500 TBI 350CI, Fuel delivery

I took the truck to filling station to get some gas for the mower, when I
went to restart it , it wouldent! Had the son drag me home with a chain!

Had a plastic Mustard jar with gas a squirted into throttal body and it runs,
so guess this means the dizzy is ok!

Found FP relay under hood last night, looks like org (power), red (prim I
think), grnwhite stripe (computer control), gray ( power to pump). Fuse is
also there 20 amp, its good!

Also found wires from FP, Gray, black white strip,Red, they go over the
frame and have a plug it that location.

So far the only thing I have done is hook up the amp draw meter and the
the key to ON position , zero amps reading.


Truck has been hesatating alittle lately, and once in a while the" check to guages" light comes on!

The trucks fuel pump is orginal, truck has 188K miles on it!

I cant find where the pumps grounds to the frame, know any locations?

Denny
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Old 06-30-2011, 12:28 PM   #2
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Alrighty this is my specialty as i have two of these trucks and had the same issue with both..here is what i know
under your hood in that junction area where you found the relays all the way to the left is a smal little relay looking thing unhook that because inside is a fuse.Check that fuse it is your FP fuse.

But due to you saying it stumbled tells me the pump its self is dead or the ground is loose..The ground on both of mine are on the Drivers side it is bolted to the bottom of the bed.OUTSIDE of the frame rail if you get under right where your filler neck is and look toward the cab you should see it.Also kick the tank (if you have steel toe boots) or tap it with a rubber hammer then try to start it.

But your symptoms sound like mine it sounds like the pump is dead.,i have replaced the pump in two of these and also a couple other parts that are wired in line with the pump that when they go bad the pump no longer runs.,

Tee oil pressure switch is in line that way if you lose oil pressure it kills power to your pump but that makes it just die suddenly with no warning(this has happend to me) it will cut the fuel pump if that switch goes bad but like i said that is an instant kill.

TO save you some trouble you may want to order gas tank staps If its a shortbed its a 25 gal tank
Anfd if its a longbed it will be a 34 gallon tank

Also if its a shortbed you will need to remove your driveshaft...Ask me how i know! one of mine is short one is long LOL

And one last thing..take your filler neck out in peices.Disconnect metal from rubber and rubber from tank .BEFORE you take the tank outakes life a whole lot easier.then assemble in reverse after tank is back in also dont even bother with the little yellow/white plug on the sending unit unhook it from the BIG plug thats in line with the wires
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Old 06-30-2011, 01:12 PM   #3
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Quote:
Originally Posted by sseidriver97 View Post
Alrighty this is my specialty as i have two of these trucks and had the same issue with both..here is what i know
under your hood in that junction area where you found the relays all the way to the left is a smal little relay looking thing unhook that because inside is a fuse.Check that fuse it is your FP fuse.

But due to you saying it stumbled tells me the pump its self is dead or the ground is loose..The ground on both of mine are on the Drivers side it is bolted to the bottom of the bed.OUTSIDE of the frame rail if you get under right where your filler neck is and look toward the cab you should see it.Also kick the tank (if you have steel toe boots) or tap it with a rubber hammer then try to start it.

But your symptoms sound like mine it sounds like the pump is dead.,i have replaced the pump in two of these and also a couple other parts that are wired in line with the pump that when they go bad the pump no longer runs.,

Tee oil pressure switch is in line that way if you lose oil pressure it kills power to your pump but that makes it just die suddenly with no warning(this has happend to me) it will cut the fuel pump if that switch goes bad but like i said that is an instant kill.

TO save you some trouble you may want to order gas tank staps If its a shortbed its a 25 gal tank
Anfd if its a longbed it will be a 34 gallon tank

Also if its a shortbed you will need to remove your driveshaft...Ask me how i know! one of mine is short one is long LOL

And one last thing..take your filler neck out in peices.Disconnect metal from rubber and rubber from tank .BEFORE you take the tank outakes life a whole lot easier.then assemble in reverse after tank is back in also dont even bother with the little yellow/white plug on the sending unit unhook it from the BIG plug thats in line with the wires
Well I think I found the ground your talking about, but it looks like it for grounging the fuel neck. (pict)

I have the short bed. Ill try clobering it with a rubber mallet to see if I can get it to run next.
I just filled the tank up!
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Old 06-30-2011, 02:03 PM   #4
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ahh yes your right i forgot it was for that lol i cant recall where the pump ground is its somewhere around the area and it always seems to happen like that.Both times mine went out i had just filled up
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Old 06-30-2011, 07:10 PM   #5
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Quote:
Originally Posted by sseidriver97 View Post
ahh yes your right i forgot it was for that lol i cant recall where the pump ground is its somewhere around the area and it always seems to happen like that.Both times mine went out i had just filled up
I looked all over for another ground wire, still cant find it.

UPDATE:
I tested the GRAY wire coming from the relay, it generates voltage for 3 seconds when the key is turned to ON position,
Test the same gray wire at the fuel tank, it has voltage also!

I beat on the bottom of fuel tank (3 smacks with rubber malet) while wife cranked and it started right up, turned it off and it started again!

I'd say it the fuel pump or its internal wiring!

What do you guys think?
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Old 06-30-2011, 08:22 PM   #6
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seems likely
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Old 06-30-2011, 09:57 PM   #7
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That grey wire is giving you power for three seconds because it is the prime wire.Usually when u hit the tank and it will run its the pump.Just check the wiring all our before you remove the pump from the SU and if all the wiring looks good then the pump is shot.In order to replace you have to take the strainer off it disconnect the short rubber hose and wiring for it to be free from the sending unit..The new pump will come with new internal wires a new tank lock o ring new clamps and small rubber tube.Strainer is an extra 10 bucks
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Old 06-30-2011, 11:49 PM   #8
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enough for today , get a jump on it tommoro.
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Old 07-01-2011, 12:29 PM   #9
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I found some stuff on top the fuel pump, looks like either grease or wax, what ever it is , it did protect the metal.

Also found the ground for the fuel pump, its the bolt that secures the plug, its under it, bad spot! (PICT)
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Old 07-01-2011, 03:44 PM   #10
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This connection worked ! But its not a very good one! Another look!
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