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

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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?

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

jesusfreak_ace wrote:
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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...

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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...


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

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Drive i9t both way and you will find MPG is better with it down at
higher speeds. It will be apparent on a long trip. As far and bed
warping, that is bizzare because they only way it can is if the bed
structure rusts out and if it does, the gate being up will not help it
because the gat does not latch against that kind of flex/strees
becuase it would simple fall down when sides warped out because it
does not lock them into place.
The SnoMan

Re: Questions about 1999 Chevy Silverado 1500 LS 4x4 Z71???
On 19 Jun 2006 10:29:40 -0700, "jesusfreak_ace"

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They tested this on the TV show MythBusters and found milage was
actually worse with the tailgate down.


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

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The real my is myth busters because I have seen first had otherwise.
It is not a very scientific test as any changes in velocity and air
dnesity can greatly change the outcome. THe real world test is take a
300 mile trip both ways and you will see that there is a difference.
The SnoMan

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

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I watched the myth busters episode also. Before that there was also a local
group that actually tested this in the real world. This was a year or so ago
when gas prices went up. A group of about 10 people did the test for our
local paper. All went 1 week up and 1 week down. The paper used vehicles
that normally traveled on the same route during the same time of day,
basically people that drove a long way to work and back. Not exact science
but pretty close. I just got done searching for the exact article but
haven't found it yet but there was a definite advantage to tailgate up. All
vehicles in the test showed a gain. This is from one year old memory but I
think a full size short bed Dodge showed over a 1 MPG increase while some
only showed a few tenths. Now for my second reason to keep the gate up.
About 4 years ago I did a frame off restore on a 78 Chevy 2wd. Through sheer
luck I found a new tailgate in Wisconsin. The tailgate had been removed for
a lift gate when the truck was new. Bought the gate for 200 bucks paid to
have it shipped UPS and then had it painted with the truck. About a month
later I crossed a rough set of RR tracks and bounced the tailgate off. Think
of how impossible this is to have the gate and arms bounce to the right
position to release but I had 2 other guys in the truck as witness. To end
the story imagine the road rash on a beautiful new 20 year old tailgate.
Never did find a replacement, ended up changing hinges and lock plates to
the ones off a 86 and using that gate. Plus a custom blended paint that
ended up not matching right on the gate. I drive with the gate up!

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