[ricksautorestoration]

I'm getting some hesitation with my 96 blazer and i'm pretty sure its my fuel pump. When i went under my vehicle to take the cover off my gas tank i notice that under the rear bumper gaurd there is a sqaure box about 10" by 10" with the fuel lines from the gas tank going into it. What exactly is this box and what does it do and is there anything in there that can be causing my problems? I changed a fuel pump in my 97 blazer last year and i did not see anything like this in that blazer. The only differance between the two is one is a four door and this one is a 2 door. Thanks to anyone that can help me with this.

[Bumpstick]

That sounds like the vapor canister which has charcoal in it to absorb the fuel vapors for recovery back into the system...

The hesitation you mention could be from other possible problems...? Might consider having it scanned with a good quality scanner...? Also time since it was last tuned up...? Fuel pumps normaly show up as a complete failure situation but they sometimes still run and cause a loss of power under demand... Or even hard starting...

[ricksautorestoration]

Thanks, it was just tuned up recently i figured its the fuel pump because its doing the same thing as my other one did it kind of struggles to get up too speed. The only differance my other one did have the hard starting problem this one doesent but i will scan it to check for any codes.

[Colada27]

I agree with bumstick, although a scanner wont do you any good if you are not getting a check engine light. The fuel pump is a go/no go item. Hesitation or loss of power (especially in the top end) can be a result of the fuel filter being clogged or possible electrical.

[ricksautorestoration]

Actually just changed the fuel filter made the problem worse it seems. I had a couple fuel pumps that took a while to go before they finally totally quit. My Grand Am i used to be able to boot the bottom of the tank with the ignition on to get it going. The vehicle has over a 150 thousand miles on it and i wouldent doubt its the original pump.

[Bumpstick]

Back to the scanner suggestion it may show lean codes on the O2 sensors...

That would most likely give you a for sure idea...

[Colada27]

Thinking deeper, i guess there is a reason they sell rebuild kits for my holley elec fuel pump. it possibly could be a worn out pump with that many miles. But not very common. The black box does sound like a vapor recovery cannister.

[ricksautorestoration]

Very interesting i have no check engine light on but i scanned and got 2 codes. A P0102 code which is the masf sensor i beleive that is between the air cleaner and the throttle body. The other one is a P0440 code which i looked up it seems to be a evap cannister? Is that the cannister behind my bumper end with the fuel lines going to it? And what would be the problem with that it?

[Colada27]

Well, I learn something new everyday! I have never known a code to show w/o the check engine light ever flashing (or has it ever?) Evap canister is just supposed to absorb the fuel vapors before they vent to the atmosphere, so I am not sure what the prob could be there. Please keep us posted, Im curious.

[ricksautorestoration]

Ya i will have to do some more research on that P0440 code but i'm sure it said something about a evap cannister. I used to get a check engine light long time ago i'm wandering if the bulb just burnt out.

[Bumpstick]

Bulb may be burnt...? But on the evap code its more than likely the valve that is in the can setup... Most of the time we also found the fuel cap was bad... (normaly said small evaporative leak)

The other could be your real problem... If the MAF is bad then for sure driveability will suffer...

[ricksautorestoration]

The bulb for my check engine light it does not come on but i have codes stored when i scan. Do i just change this maf sensor or its just the part thats between the air cleaner and the throttle body i beleive or is there something i can try before changing the sensor? Thanks you guys are a lot of help.

[Ricky Rocket]

Throwing parts at the Blazer will be expensive, especially a MAF. You are better off to find the diagnostic chart for your codes and follow them through. Problem could be wiring or something else. Your check engine light should be on with the key on, engine off - this lets you know the bulb is working.

Good luck,
Rick

[brokebyford]

Had the same exact problem with my blazer.It turned out that the rubber vacuum lines had become brittle and cracked.After spending too much money chasing codes and doing a Mass Air sensor the cheap new rubber hoses fixed all the codes and problems.

[T-bucket23]

I doubt your issue is the fuel pump or the canister. The MAF code makes sense with the symptoms you have given. It sounds like a fuel or air metering problem to me. Sometimes the MAF wires can be cleaned, you need to be careful you dont break them. A lot of vehicles will run with the MAF disconnected, it will go into a limp home mode an control fuel without the MAF.