bad fuel pump?

[98BlazerLT]

my gas guage drops very slowly during the first 1/4 of a tank then when it gets to about 150 miles you can literally watch the needle drop for the other 3/4. one time it almost stalled while sitting at a stop light and every once in a while the whole vehicle vibrates when it is started until it is put in gear. could this be the fuel pump going bad? i know the sending unit needs to be replaced but i don't want to replace the entire unit unless i have to.

[old_master]

Due to the asymmetrical configuration of the fuel tank, the gauge can not indicate the fuel level accurately through the entire range. As for the fuel pump, a fuel pressure check will determine the condition of the pump.

[98BlazerLT]

my guage has always been fairly accurate until a few tanks ago. with each tank the needle drops slower and slower in the top 1/4 of the tank. thanks for the fuel pressure check info, i'll try it tomorrow.

[dmbrisket 51]

not sure if our tankes have balffles in them or not, if they do, that could be an issue... and even if the pump is still good, sounds like the sender is shot... good, QUALITY pumps come as a fuel sending unit, meaning pump and sender assembled into one...

[98BlazerLT]

last week the shop i go to didn't sound like they thought it was important that the sending unit be replaced immediately. they recommended waiting until the fuel pump needs replaced but said the stalling could be a symptom of the fuel pump going bad. what do you guys think a shop might charge to check the fuel pressure?

[dmbrisket 51]

we get an hours labor for it... ranging from 45 to 90 bucks depending on your area

[wolfox]

The reason why they say wait is because on your year/model truck, the sender and pump assembly is an integral part. You can live with a ditzy fuel gague, but not with a bad/weak fuel pump. Again, I would back the other guys up and say to check your fuel system's pressure with a gage. They are not expensive. I got one with an adapter kit to match Ford and various European models with fuel rail taps for $25. Also, if you haven't, check and replace your fuel filter. If you do not recall doing it in the past year of ownership, it will be about time. The filter can be clogged with fine tank crap that the strainer sock and fuel pump can pass easily, but will not pass through an injector happily. If the engine hesitates/quits under load or demand, like say, passing speeds on the highway - definitely replace the filter first if your fuel pressure checks out @ idle. They're only like $8-$12/piece and the cheapest thing that you can do to save yourself headaches when you suspect fuel delivery issues.

[BlazinMlew]

Originally Posted by wolfox

The reason why they say wait is because on your year/model truck, the sender and pump assembly is an integral part. You can live with a ditzy fuel gague, but not with a bad/weak fuel pump. Again, I would back the other guys up and say to check your fuel system's pressure with a gage. They are not expensive. I got one with an adapter kit to match Ford and various European models with fuel rail taps for $25. Also, if you haven't, check and replace your fuel filter. If you do not recall doing it in the past year of ownership, it will be about time. The filter can be clogged with fine tank crap that the strainer sock and fuel pump can pass easily, but will not pass through an injector happily. If the engine hesitates/quits under load or demand, like say, passing speeds on the highway - definitely replace the filter first if your fuel pressure checks out @ idle. They're only like $8-$12/piece and the cheapest thing that you can do to save yourself headaches when you suspect fuel delivery issues.

I agree. You can live with the bad gauge reading and there is really no point replacing the sending unit and not the pump because you have to drop the tank anyway. With a bad sending unit you can last anwhere from 3 days to 3 years on that fuel pump. Mine lasted just over 3 years, then I just had the whole thing replaced. But check your other options first and save yourself the headache.