Author Topic: '79 K1500 fuel pump?  (Read 3971 times)

Offline MechanicallyIgnorant646

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'79 K1500 fuel pump?
« on: January 15, 2020, 10:57:36 PM »
So I've had an ongoing series of problems with this vehicle as it sat for the better part of 10+ years and the shop I took it too failed to be as thorough as I'd asked but that's another story altogether...

So what's happening now is the truck has had a tendency to drain batteries, guage failures etc.. so this MAY be an electrical problem..
But a few days ago I was driving, shoot it off parked on a slight incline. Then could not start it. Jumped it off.. it's happened before.
But this time I noticed the fuel.filter under the hood was sputtering, gushing gas and not quite filling up. Usually it stays full unless I let it sit for days or weeks. Sputtering/spewing filter aside, it started with jumper cables on battery and then ran fine. The next day it started and ran just fine. Then the next day it wouldn't start and I'm getting no fuel in that filter. Both filters from each tank have fuel in them.

When I turn the key to on position I can hear a wirring/humming sound like a fan but it doesnt seem to be coming from the fuel pump.

It may be worth mentioning that if I use the tank selector switch under the dash it will blow a fuse IF the ignition is on. If I do it with the ignition totally off it will seem to switch tanks just fine with the guage reacting to whichever tank I've switched to. I'm not sure if that could be relevant to the other issue.

I hope this wasnt too much or confusing.

Offline bd

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Re: '79 K1500 fuel pump?
« Reply #1 on: January 16, 2020, 10:10:36 PM »
It may be worth mentioning that if I use the tank selector switch under the dash it will blow a fuse IF the ignition is on. If I do it with the ignition totally off it will seem to switch tanks just fine with the guage reacting to whichever tank I've switched to. I'm not sure if that could be relevant to the other issue.

The tank selector and gauge should not operate with the ignition off.  I agree.  It has an electrical issue.  Begin by having the battery charged and tested.  Then strat searching for parasitic draws.

The hum/whir may be the blower motor.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline MechanicallyIgnorant646

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Re: '79 K1500 fuel pump?
« Reply #2 on: January 17, 2020, 05:28:40 AM »
What I meant is that if the ignition is off and I flip the switch, and then turn on the ignition, that's when the guage needle moves indicating tank change.

But if I flip the switch with the ignition on, it blows a fuse.

Offline bd

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Re: '79 K1500 fuel pump?
« Reply #3 on: January 17, 2020, 09:31:21 AM »
The switch may be shorting internally as its contacts move.  Does the tank solenoid actuate?  Try disconnecting the tank solenoid then flip the dash switch.  Does it still blow the fuse?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline MechanicallyIgnorant646

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Re: '79 K1500 fuel pump?
« Reply #4 on: January 18, 2020, 07:07:06 AM »
Where is that solenoid located? Tried an internet search and came up.

 The handle is no joke lol I know little to nothing about these matters.
Pretty broke too, need to get a service manual.

Thanks for the help guys.

Offline bd

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Re: '79 K1500 fuel pump?
« Reply #5 on: January 18, 2020, 09:07:39 AM »
The fuel tank solenoid should be located below the cab, above and behind the transmission toward the passenger side frame rail.

The 1973-87(91) Factory GM Pickup Manuals are available in the Technical Forum under General Information and Maintenance.  Pick and choose the manuals you need.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline MechanicallyIgnorant646

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Re: '79 K1500 fuel pump?
« Reply #6 on: January 18, 2020, 09:13:40 AM »
VileZambonie also just posted a link to those for me in the 4x4 section.

I really appreciate the help. I'm going to take some time to review the manual.

Thanks again!

Offline bd

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Re: '79 K1500 fuel pump?
« Reply #7 on: January 18, 2020, 11:38:00 AM »
The manuals may not answer every question you have.  They assume the user has at least a fundamental understanding of automotive systems and basic repair skills.  You might consider attending a beginning course in automotive technology at your local community or vocational college.  It could provide an invaluable orientation.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)