Constantly blowing fuel pumps! Please Help!!!!!!!!

McCool said:
Alright so I think I found a part of my problem

Here is a look at the wire harness leading from the top of the fuel sender to the pump and to the sender itself:
Fuelpumpwire-1.jpg


Slightly larger view:
http://i850.photobucket.com/albums/ab65/McCoolium/IMG_3068.jpg

It might be a bit hard to see but the two wires that are circled appear to be burned. the two wires both lead to the fuel pump. Now obviously these need to be replaced (I assume that means I need to buy another fuel sender). But the bigger question is, What caused the wires to burn out like this? Any Ideas?

Another question, Do I need to replace this wire harness (this is the one on the top of the Fuel sender:
Topoffuelpump.jpg



Thanks guys!
Click to expand...

Most of the time the wires in the unit is good since it's being cooled by the gas in the tank, unless you drive with your fuel less then 1/4 fuel most of the time. What causes your wires to melt like you showed is low fuel in the gas tank, dirty fuel filter causing your pump to draw more amp, and running out of fuel causing your pump to burnout.

Inspect the leads clip to your sending unit and see if it's also damaged like the wires leads you have just inspected that have damage. Good luck and keep us posted and great job on doing what a mechanic seems to can not find wrong with your Sierra. ;)
 
Alright so I pulled the sender out of the tank, here is what I've found:

1) As the picture from my previous post shows, the wire that connects from the top of the fuel sender to the fuel pump is burnt on both ends of the connection. Like you said this was probably caused by the pump drawing too many amps (the last pump blew because the filter was clogged)

2)The ground wire that came from the fuel sender was severely corroded at its connection to the frame (which might have been my problem.)

3) I hooked the fuel sender up to a ohm meter and no matter how I manipulate the wires they always maintain continuity. Which suggests to me that they are not to problem.

So here's my plan; I am going to replace the sending unit, I am going to clean up the ground and I am going to put di-electric grease on all the connections.

I am going to change out the sending unit because even though the wires don't seem to be broken, having burnt wires can only lead to premature failure.

What do you think Molson... does this sound like a solid plan or is there something else I should consider?

Thanks
 
McCool said:
Alright so I pulled the sender out of the tank, here is what I've found:

1) As the picture from my previous post shows, the wire that connects from the top of the fuel sender to the fuel pump is burnt on both ends of the connection. Like you said this was probably caused by the pump drawing too many amps (the last pump blew because the filter was clogged)

2)The ground wire that came from the fuel sender was severely corroded at its connection to the frame (which might have been my problem.)

3) I hooked the fuel sender up to a ohm meter and no matter how I manipulate the wires they always maintain continuity. Which suggests to me that they are not to problem.

So here's my plan; I am going to replace the sending unit, I am going to clean up the ground and I am going to put di-electric grease on all the connections.

I am going to change out the sending unit because even though the wires don't seem to be broken, having burnt wires can only lead to premature failure.

What do you think Molson... does this sound like a solid plan or is there something else I should consider?

Thanks
Click to expand...

Sounds good, and you will get good continuity when the wires are cold, it's when the electrical flow heats up the wires is when you have the issues. The insulator is hard and keeps the wire inside all together, and when it's heats up. It's more to flex and expand causing the issues your having. Good luck and keep us posted and make sure you have a great ground when putting everything back together. Bad ground causes the wires to heat up more. :eek:

Please keep us posted and great work done.
 
Well It's all back together. I lucked out really hard too, I went to parts source to get a new sending unit but they only carried one with the fuel pump and they wanted $490 for it. I was pretty close to buying it but I called Napa and they had the sending unit for $170 but I get a discount there and I ended up paying $120. How cool is that?

Anyways the install went off without a hitch, I cleaned up the ground and hit it with some di-electric grease. the pump is engaging just fine for right now so I hope that this will solve the problem. The only thing I didn't like was how the sock filter attached to the pump, seems to me like it could fall off pretty easily.

I do have two questions though:

1) So all the wires in the sending unit will be submerged in gasoline when the tank is full? that seems a little odd to me, how does this not cause shorting or even more critically, arcing?

2) For the sake of argument, lets say that the pump continues to fail intermittently what would be my next step towards fixing the problem?

Thanks
 
McCool said:
Well It's all back together. I lucked out really hard too, I went to parts source to get a new sending unit but they only carried one with the fuel pump and they wanted $490 for it. I was pretty close to buying it but I called Napa and they had the sending unit for $170 but I get a discount there and I ended up paying $120. How cool is that?

Anyways the install went off without a hitch, I cleaned up the ground and hit it with some di-electric grease. the pump is engaging just fine for right now so I hope that this will solve the problem. The only thing I didn't like was how the sock filter attached to the pump, seems to me like it could fall off pretty easily.

I do have two questions though:

1) So all the wires in the sending unit will be submerged in gasoline when the tank is full? that seems a little odd to me, how does this not cause shorting or even more critically, arcing?

2) For the sake of argument, lets say that the pump continues to fail intermittently what would be my next step towards fixing the problem?

Thanks
Click to expand...

You should be fine and the sending unit has a life expectancy of 150,000 miles and will be shorten if the fuel pump works in a heated condition from running low fuel and dirty fuel filter. There was a link i gave you on the earlier post on to how to replace the pump alone from your sending unit for a upgraded pump.

The wires that is submerged in the gas tank are highly insulated, but will break down over time. Great job and keep us posted on your Sierra. ;)
 
It's seems to be running fine. But since it was an intermittent problem only time will tell. Thanks for the help Molson. Next up; Changing out my water pump.
 
sounds like you wanted it done right so you did it yourself. good job
 
2 months of driving and it is doing great. let this be a lesson to everyone, if you are changing the fuel pump give your sending unit a look over, it might save you a huge heart ache!!!

P.S. If you are changing you fuel pump, lifting the bed of the truck is way easier than dropping the tank. Just have a can of wd-40, a long extension and 2-3 cans of beer handy.

Thanks for the help guys
 
How do you think that removing the bolts on the drivers side, loosening the bolts on the passenger side, then jacking and supporting the bed would do? I'm just thinking about a one-person DIY... Ron
 
sorry for the delay in reply :S

Honestly your best bet is to call 3 friends over for when you need to lift the bed. I did it with just myself and a buddy but 4 people would have been nice.
 
Just got airtex pump and sending unit for 98 bucks. my 92 jimmy has 192000 miles on it. any one know if that will hold for a while?
 
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