Questions about 1999 Chevy Silverado 1500 LS 4x4 Z71???

I have a few questions about a 99 Chevy Silverado 1500 LS 4x4 Z71 that
i was hoping SOMEONE could answer for me.

1) I'm looking for better ways to improve gas mileage...whenever i
drive over 60 mph i put the tailgate down...does this really help? Also
which 4x4 setting should i have selected while driving? Obviously
neither HI or LOW 4x4 is a good choice but there is also a choice of 2
HI or 4x4 Auto AWD. Which one would be a better setting to save gas and
would be easier on my engine?

2) Recently my fuel pump went out and i had a friend replace it who is
a certified mechanic. However, since then when i try to start it up for
instance on a hot day or if it had been running for awhile before i
turned it off then it will "churn" for a little while before it fires.
In the mornings and when cooled off it starts up with no problems. What
could this be? Is it simply a starter going bad or did the timing get
thrown off somehow? Keep in mind this only happened AFTER my friend had
replaced the fuel pump...nothing was touched other than that during the
process but could this have triggered something else?

jesusfreak_ace wrote:
> I have a few questions about a 99 Chevy Silverado 1500 LS 4x4 Z71 that
> i was hoping SOMEONE could answer for me.
>
> 1) I'm looking for better ways to improve gas mileage...whenever i
> drive over 60 mph i put the tailgate down...does this really help? Also
> which 4x4 setting should i have selected while driving? Obviously
> neither HI or LOW 4x4 is a good choice but there is also a choice of 2
> HI or 4x4 Auto AWD. Which one would be a better setting to save gas and
> would be easier on my engine?

I've heard having the tailgate down does not help, and it's rumored
that over time the sides of the bed could warp somehow, ending up being
too close or too far apart, and that could lead to problem shutting the
tailgate. I don't know if there's any truth to the 2nd part, but I've
seen many reports where having the tailgate down or removed did NOT
help fuel economy.

I've heard the best thing for that is a smooth bed cover of some sort.

2WD Hi should be your best bet for fuel economy. I'm not familiar
enough with Z-71's, so I don't know what kind of locking mechanism is
used for the front hubs. It may be a situation where the front axle is
engaged (and therefore spinning) the whole time, in which case I can't
imagine keeping it in 2WD would help. If so, you'd still have the
resistance of the front end fighting you...

> 2) Recently my fuel pump went out and i had a friend replace it who is
> a certified mechanic. However, since then when i try to start it up for
> instance on a hot day or if it had been running for awhile before i
> turned it off then it will "churn" for a little while before it fires.
> In the mornings and when cooled off it starts up with no problems. What
> could this be? Is it simply a starter going bad or did the timing get
> thrown off somehow? Keep in mind this only happened AFTER my friend had
> replaced the fuel pump...nothing was touched other than that during the
> process but could this have triggered something else?

Where's the "churning" sound coming from? If you turn the key to the
"on" position, but don't actually try to crank it, you should hear the
electric fuel pump "churn" for a couple of seconds while it's building
the fuel pressure necessary to start the engine. That's normal. If
you weren't hearing that sound before, it was probably part of the
reason (or symptom thereof) that the fuel pump needed to be replaced in
the first place.

Not sure on the hot-start issue. I've experienced hot-start troubles
in the past, but they weren't the kind you're talking about. It *was*
related to the starter, but it was a problem with a mis-matched starter
and flywheel. When the engine was hot, meaning recently run and with
higher residual oil pressure (and hence compression) the starter would
lose its grip on the flywheel and makes a very loud grinding/scraping
noise. There's no mistaking that sound.

I can't imagine what the fuel pump would be doing differently while
cold as opposed to while hot. It should pulse (churn) for a second on
startup regardless to build up fuel pressure.

Maybe someone else knows...

~jp