5.3L Vortec Fuel Problems

[Mug]

My tow rig is a '00 GMC Sierra and lately it's mileage has dropped by about 20%!

At first I had fuel delivery problems. aka no fuel was getting past the filter. When I took it out, there was something rattling inside - not good. I replaced that, but I think it had already overworked the in-tank pump, and it had died. I replaced that too and that's when I noticed the mileage problem. I had a mechanic friend look for any maintainance advisories for the model and he came up with the fuel pressure regulator. So what did I do? Replaced that too. Still nothing.

Has anyone else had this problem? Any leads would help.

 

[wagonmaster]

Two ideas I can think of: First you may have injested something into an injector from the contamination of the fuel system that has a pintle stuck part way open and therfore always leaking fuel into the engine at all times, Second you may also have a bad upstream oxygen sensor and therefore the computer is unable to determine proper A/F ratio and consuming more fuel than necessary. This scienerio is possible without setting engine light.

 

[Mug]

Two ideas I can think of: First you may have injested something into an injector from the contamination of the fuel system that has a pintle stuck part way open and therfore always leaking fuel into the engine at all times, Second you may also have a bad upstream oxygen sensor and therefore the computer is unable to determine proper A/F ratio and consuming more fuel than necessary. This scienerio is possible without setting engine light.

I will look into both of these scenarios. THANK YOU!

 

[UNSTUCK]

If one is stuck open, you shouldn't hear or feel it clicking.

 

[MikeGyver]

My tow rig is a '00 GMC Sierra and lately it's mileage has dropped by about 20%!

Has your wife been driving it?

Surely the check engine light is on, just take it to Vatozone and have it scanned.
It's probably got a bad o2 sensor, or possibly clogged cat?

If you suspect a stuck fuel injector perform a fuel pressure leakdown test. Key on, wait for the prime pulse, if there are any leaks the fuel pressure will continually drop.

 

[rholbrook]

My experience, though not because I am a mechanic or claim to be one has been a plugged injector on one of my vehicles and on another was a bad pulley(wasn't noisy) and on another instance, bad AC compressor. All three significantly affected my mpg.

 

[Mug]

Has your wife been driving it?

No , just me.

Surely the check engine light is on, just take it to Vatozone and have it scanned.
It's probably got a bad o2 sensor, or possibly clogged cat?

If you suspect a stuck fuel injector perform a fuel pressure leakdown test. Key on, wait for the prime pulse, if there are any leaks the fuel pressure will continually drop.

And no dummy message.

I'm gonna look into it more.

 

[78mitsu]

Has it had a tuneup recently? I had a similar problem on my '02 ended up needing plugs. $16 later it was running like a champ. They are Aluminum heads so be careful changing plugs.

 

[schaeferNsons]

i would check to see if the mass air flow sensor is reading correctly, and i would try cleaning the injetors with a good cleaner such as bg 44k, or the gm product that you can get from the dealer, and i would have the back pressure check to see if you have a plugged cat or muffler, and they have a double wall pipe on the down tube and i have seen a few of those collapse. let me know if i can help any more