I regularly run DataMaster scans on my truck while driving to and from work. Over the past two weeks I noticed my BLM's slowly going higher and higher, some were as high as 140 during cruise. I thought I had gotten them to be pretty close to 128.

This morning I filled up the 31 gal. gas tank with 27 gal. Now my BLM's are back to being around 128. Same cruise speed, same roads, etc.

That's got me wondering if my fuel pump is going bad. Doesn't the pump pressurize the whole fuel tank? (EDIT: After thinking about it, that seems like a stupid statement on my part ) I'm thinking that, for some reason, the pump might not be able to keep the same pressure when there is less fuel in the tank. On the other hand, I always thought that when pumps fail they just stop working.

BTW, the fuel filter only has about 500 miles and I've rebuilt the TBI recently.

Thanks

 

If you are still getting fuel under full throttle conditions then your fuel pump is probably OK. If you want to know for sure install a fuel pressure gauge. E-mail me if you want to see how I installed a fuel pressure gauge in my car.
'99 AG!

 

Pull out the fuel pump fuse and put an amp meter (ammeter)in its place, you should draw 3-4 amps, if it is drawing less, the pump is likely bad.