A new noise (85 245)

[Blazer Fan Dan]

So far, I've asked about my heater blower and my rear dif, and maybe
something else. I don't recall.

So now, I have a new question. I heard a noise in the back, and
figured it was a rear dif issue, so I asked here. And it was suggested
it was either the fuel pump or the rear dif. Because of the
description of the noise I heard, I was told to check the rear dif
lube level. So I checked it today, and it was low (I don't know HOW
low, but it was low). So I filled it and it seems to be better now.

But now I hear a different noise. And I do realize some of that might
be just me being paranoid, but I'm not sure. When I started it under
the deck (enclosed) I heard what sounded like my heater blower motor
fan on coming from the back.

When I would drive, it would be drowned out and eventually go away.
And sometimes when I am at a stop light, it appears again. It does not
change based on my speed, the speed of the engine, or if I'm coming or
going. If I pump the gas pedal, it makes no difference either.

My friend says it doesn't sound like a fuel pump issue (I'm hoping
it's not, thats not cheap to fix) because it doesn't have the sound to
match what he thinks it sounds like (and because of the amount of gas
I have in my tank, almost full, it doesn't sound like a pre-pump issue
either).

Any ideas?

 

[James Sweet]

So far, I've asked about my heater blower and my rear dif, and maybe
something else. I don't recall.

So now, I have a new question. I heard a noise in the back, and
figured it was a rear dif issue, so I asked here. And it was suggested
it was either the fuel pump or the rear dif. Because of the
description of the noise I heard, I was told to check the rear dif
lube level. So I checked it today, and it was low (I don't know HOW
low, but it was low). So I filled it and it seems to be better now.

But now I hear a different noise. And I do realize some of that might
be just me being paranoid, but I'm not sure. When I started it under
the deck (enclosed) I heard what sounded like my heater blower motor
fan on coming from the back.

When I would drive, it would be drowned out and eventually go away.
And sometimes when I am at a stop light, it appears again. It does not
change based on my speed, the speed of the engine, or if I'm coming or
going. If I pump the gas pedal, it makes no difference either.

My friend says it doesn't sound like a fuel pump issue (I'm hoping
it's not, thats not cheap to fix) because it doesn't have the sound to
match what he thinks it sounds like (and because of the amount of gas
I have in my tank, almost full, it doesn't sound like a pre-pump issue
either).

Any ideas?

Given the age, I suspect the rubber bellows attaching the pre-pump in the
fuel tank to the pickup tube. To get to that, get under the car and
disconnect the union in the high pressure line, then open the access panel
inside the car and disconnect the return, vent, and wires from the tank
bung. Remove the bung nut and pull out the pump/sender assembly. You'll find
a rubber accordion hose between the pump and pickup tube, which will very
likely be split. Replace it with a length of 3/8" fuel hose, or order the
correct part and reassemble, the noise should be gone.

 

[Blazer Fan Dan]

Given the age, I suspect the rubber bellows attaching the pre-pump in the
fuel tank to the pickup tube. To get to that, get under the car and
disconnect the union in the high pressure line, then open the access panel
inside the car and disconnect the return, vent, and wires from the tank
bung. Remove the bung nut and pull out the pump/sender assembly. You'll find
a rubber accordion hose between the pump and pickup tube, which will very
likely be split. Replace it with a length of 3/8" fuel hose, or order the
correct part and reassemble, the noise should be gone.

While I will fix it, is it a huge mechanical/running issue if I don't
get to it right away?

 

[James Sweet]

While I will fix it, is it a huge mechanical/running issue if I don't
get to it right away?

It's hard on the main fuel pump. If you keep the tank full the noise will
probably go away, the problem is only when it gets down to about half. It
won't cause any immediate damage.

 

[Blazer Fan Dan]

It's hard on the main fuel pump. If you keep the tank full the noise will
probably go away, the problem is only when it gets down to about half. It
won't cause any immediate damage.

hm...I have mostly a full tank though, and the noise is evident.