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

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McCool

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I have a 1997 1500 5.7l

1 week ago my truck wouldn't start, I was getting crank, spark but no fuel pressure. I took the truck to a shop, they replaced the fuel pump, it worked great for a week and then all of a sudden I tried to start it and nothing. Once again I have crank, spark but No fuel pressure.

The previous owner claimed that he replaced the fuel pump shortly before I bought the truck (which the mechanic who replaced the pump for me confirmed). What would cause my truck to blow 3 fuel pumps in under 1 year?

If I can't find a solution to this problem I am going to need to junk this truck because it is not worth the cost as I have spent over $3000 for one months worth of run time

Please help!!
 
McCool said:
I have a 1997 1500 5.7l

1 week ago my truck wouldn't start, I was getting crank, spark but no fuel pressure. I took the truck to a shop, they replaced the fuel pump, it worked great for a week and then all of a sudden I tried to start it and nothing. Once again I have crank, spark but No fuel pressure.

The previous owner claimed that he replaced the fuel pump shortly before I bought the truck (which the mechanic who replaced the pump for me confirmed). What would cause my truck to blow 3 fuel pumps in under 1 year?

If I can't find a solution to this problem I am going to need to junk this truck because it is not worth the cost as I have spent over $3000 for one months worth of run time

Please help!!
Click to expand...

#1 cause for fuel pump failure is a bad ground causing the pump to run hotter and running with less then 1/4 tank most of the time. It's the fuel in the tank that keeps the fuel sending unit cooled, and the lower the fuel. The hotter the sending unit will be, remember the fuel from the return line will be hotter so it's a good idea to keep at least over 1/4 of gas in your tank.

Also refueling with close to empty will cause your pump to fail earlier. With your pump begin hot and adding cold fuel in to your tank will cause your pump to contract fast and the piston and cylinder sleeves will have a tighter clearance which promote wear. Remember the sending units are only rated for 150,000 miles and anything longer then that is considered borrowed time.

Long story shore, make sure the sending unit has a good ground and that the fuel filter is changed once a year and try to keep the gas tank more then 1/4 from empty and try not to wait till your gas tank is almost empty before re fueling. :D

Good luck and hope this helps.;)
 
Many replacement fuel pumps are low quality and have a high failure rate. I do business with several shops that refuse to install anything buy OEM pumps (AC Delco, Motorcraft etc). They claim and I have long head this, there are just too many failures with these cheaper (made in China) parts. Don't let the well known brand name fool you, most if not all are the same manf, just different box.

I know someone who has gone thru a similar thing (2 pumps in as many months) and once he buckled down and paid for the AC Delco pump, never had anymore problems.

So don't discount the brand as the problem.
 
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So the sending unit has the ability to blow fuel pumps?

The filter is 1 week old just like the fuel pump. I haven't even gone through one tank of gas yet (I am at half a tank).

I spent $800 8 days ago to have the pump installed and having it die on me yesterday has really shaken my confidence in this vehicle...

So my best bet is to take a look at the sending unit????
 
Alright so I took the truck to the shop. Once it was there it started up fine...

wtf is wrong with this truck...
 
McCool said:
Alright so I took the truck to the shop. Once it was there it started up fine...

wtf is wrong with this truck...
Click to expand...

Was your wire hanress replaced along with your sedning unit??? Common for the wire's in the insulation to break and the insulation to crack on the old wire harness. :eek:
 
constantly blowing fuel pumps

had a 98 sierra,learned a few things.first is never trust your mechanic.its ok to deal with them, but dont trust him. second ,any fuel level even near a quarter tank is death to a pump.the rule is not to be more than a quarter tank from full.third and most important is if you want someting done right you gotta do it yourself,especially if your doing it for someone else,ironic huh?technicaly speaking heres what i did.on the fuel rail is a test port. hook a gauge to it turn the key on.if the pressure is under seventy pounds your pump is on the brink of death.my problem was intermittant so i checked working and when it would stall.sixty five pounds will not start your truck but sixty eight might.also as much as your pumps been changed its possible that someone dropped somthing in the tank accidentaly.it would be hard to trust that they couldnt have.impossible in fact. good luck, let us know what you find for the benefit of all.
 
Molson02536 said:
Was your wire hanress replaced along with your sedning unit??? Common for the wire's in the insulation to break and the insulation to crack on the old wire harness. :eek:
Click to expand...


It seems to me that if this is a problem with an electrical connection shouldn't I loose fuel pressure while driving (Say hitting a bump causes me the connection to break). The car never looses fuel pressure while driving, only when I turn the car off does it sometimes not build pressure again.

The sending unit was not replaced and I doubt any wires were replaced when I had the pump installed. Is this likely the source of my problem?

Just for my own knowledge, the only things that would stop a fuel pump from building pressure are:
1) blown fuse
2) blown relay
3) broken wires
4) Faulty sending unit
5) Bad pump

Is this correct? or is there another system that affects the functioning of the Fuel pump.
 
McCool said:
It seems to me that if this is a problem with an electrical connection shouldn't I loose fuel pressure while driving (Say hitting a bump causes me the connection to break). The car never looses fuel pressure while driving, only when I turn the car off does it sometimes not build pressure again.

The sending unit was not replaced and I doubt any wires were replaced when I had the pump installed. Is this likely the source of my problem?

Just for my own knowledge, the only things that would stop a fuel pump from building pressure are:
1) blown fuse
2) blown relay
3) broken wires
4) Faulty sending unit
5) Bad pump

Is this correct? or is there another system that affects the functioning of the Fuel pump.
Click to expand...

Bad ground wire which is separate from the sending unit wire harness, believe the ground wire is along the gas fill tube. Most of the time, you will not loose connection when the pump is running. The wire will heat up and expand in the insulator which will keep the wire from loosing connection, when you turn your ignition off and the pump stops working. The wires contract causing a brake, as the ignition is turned on trying to run the pump. The brake is small enough that there is a good chance that there is arching and once the wires heat up and expand again. There is enough current flow for the pump to work 100% again.

As mentioned earlier, good practice to replace the wire harness to the sending unit once it's been manipulated. Also try swapping out your fuel pump relay with another relay to see if that is where the problem is.
 
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And the sending unit is located in the tank correct?
 
McCool said:
And the sending unit is located in the tank correct?
Click to expand...

Sending unit is the whole assembly to your fuel pump system. Here is a link so you can visualize the sending unit and where the fuel pump is located in the sending unit with the wire leads.

Keep me posted and feel free to ask anymore questions. ;)

http://www.compnine.com/index.php?u...delid=6897&capuid=1&majorgroup=03&grouptype=B
http://www.compnine.com/index.php?u...delid=6897&capuid=1&majorgroup=03&grouptype=B
http://www.compnine.com/index.php?u...delid=6558&capuid=1&majorgroup=03&grouptype=B
 
alright now I am confused...

You are saying that I need to change the wires leading to the fuel pump from the relay because they probably have a break in them right?

Aside from the relay, or the wires running to the fuel pump or the fuel pump itself nothing else could cause the pump to run intermittently right?
 
McCool said:
alright now I am confused...

You are saying that I need to change the wires leading to the fuel pump from the relay because they probably have a break in them right?

Aside from the relay, or the wires running to the fuel pump or the fuel pump itself nothing else could cause the pump to run intermittently right?
Click to expand...

You got it, if there was any other issues. The "check engine" light would go on to indicate a problem such as a faulty oil pressure sending unit. A electrical brake or bad fuel pump would not cause a "check engine" light to come on.

Here is a link to what i have done with the fuel pump on my 1996 Jimmy and have not had any issues since then and cost about $99.00 for the pump. :D

http://gmcowners.com/gmc-forum/showthread.php?t=14955
 
So I need to drop the tank, change the wires inside the sending unit (including the ground)

And I also have to change the harness leading to the sending unit?

If this is correct then that means I have to drop the tank. I heard talk of it being easier to raise the bed rather than drop the tank, how do I do this?

Edit - I forgot to ask where would I get the wire harness for the sending unit? Is that a part Can-tire or Parts source carries?

Edit again - I just picked the truck up from the shop and the mechanic said that he couldn't find anything wrong. He said the relay checked out fine, and the pump always built pressure with no problems (he checked it three times on three different days). He said that it's possible that the ignition module has something to do with this problem. I didn't think that ignition module had anything to do with the fuel pump. Could the ignition module cause my pump to work intermittently???
 
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McCool said:
So I need to drop the tank, change the wires inside the sending unit (including the ground)

And I also have to change the harness leading to the sending unit?

If this is correct then that means I have to drop the tank. I heard talk of it being easier to raise the bed rather than drop the tank, how do I do this?

Edit - I forgot to ask where would I get the wire harness for the sending unit? Is that a part Can-tire or Parts source carries?

Edit again - I just picked the truck up from the shop and the mechanic said that he couldn't find anything wrong. He said the relay checked out fine, and the pump always built pressure with no problems (he checked it three times on three different days). He said that it's possible that the ignition module has something to do with this problem. I didn't think that ignition module had anything to do with the fuel pump. Could the ignition module cause my pump to work intermittently???
Click to expand...

Correct, it's much easier to lift the bed from the frame since there is only 8 nuts and blots holding it down and the electrical wires that can be unclipped at the harness. Once the bed is off, then you can inspect the electrical connection to your sending unit. I am kinda leaning towards the connection on top of the sending unit, there common to crack and water get's in and start corroding the wire leads. The corrosion then starts the electrical nightmare your having.

Never take short cuts when working on the sending units, always bits you in the long run when all the components have not been replaced in a system like the sending unit. :eek:
 
And if I need a new harness I can get that easily from a parts store?
 
McCool said:
And if I need a new harness I can get that easily from a parts store?
Click to expand...

Napa, Parts Source or even the parts department at the GM dealer and the price there is not that bad as the After market harness. Remember on what we have mentioned earlier about not taking short cuts on the fuel system, so i would just go and buy the OEM harness. ;)
 
I will be lifting the bed tomorrow, once I have access to the top of the tank is there anything else I should be on to look out for?
 
Alright, I have lifted the box of the truck, I have full access to the top of the tank, I haven't taken the sending unit out (I took a break for supper) but I am going to take it out now. I plan on replacing the harness like molson said but I was wondering if there is any way I can test the harness to be 100% sure that it is my problem (eg hook a multimeter to it)

Thanks guys
 
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!
 
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