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?

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jesusfreak_ace wrote:

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...

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

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wrote:

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 www.thesnoman.com

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On 19 Jun 2006 10:29:40 -0700, "jesusfreak_ace"

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

--Ben

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wrote:

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 www.thesnoman.com

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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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