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What would cause such a drop in MPG?

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Old 10-14-2006, 10:01 PM
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What would cause such a drop in MPG?

When I bought my 96 a few months ago, it was sitting for about 6 months w/o being started. The truck has good days and bad days. The p.o. took it on a trade for another vehicle and he drove it from GA to Arizona and back the first week he got it. He is a good friend so I belive him when he says the truck got between 20-21 mpg. After siting on his lot for about 6 months I bought it. When I picked it up the truck was hard to start. So I changed the fuel filter and oil, and added fuel treatment to it. I have yet to get more than 14 mpg no matter how or where I drive. The truck also seems to lack power, what all should I check for? It starts easy and seems to run smother when it's cooler out. Any suggestions?
Old 10-15-2006, 11:57 AM
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First thing to do is check for slipped timing and have it set at 16°
Old 10-15-2006, 12:16 PM
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Yea, I'm going to Garmon's Diesel Performance on tuesday to have it set. Why do some set it a 14.5, 15.5, or 16? What's the difference?
Old 10-15-2006, 05:50 PM
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I think it must have something to do with changes made in different production years. Here is a good site for some more info. http://dodgeram.org/tech/dsl/FAQ/timing.htm
Old 10-15-2006, 05:56 PM
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Originally Posted by wilderness
Yea, I'm going to Garmon's Diesel Performance on tuesday to have it set. Why do some set it a 14.5, 15.5, or 16? What's the difference?
I don't think many folks have the timing reset at less than 16 on purpose, many go higher. The lower numbers are almost stock.
Old 10-15-2006, 07:38 PM
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If your going to pay to have it set , get it bumped up to 17.5 or 18 degrees , this will definetly help with fuel milage , i did mine this weekend.
Old 10-16-2006, 01:05 PM
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Originally Posted by JKM
If your going to pay to have it set , get it bumped up to 17.5 or 18 degrees , this will definetly help with fuel milage , i did mine this weekend.
Ur puttin the stock head gasket

at risk with anything over 17, i myself have it at 16.5 degrees, and saw a 2MPG increase.... 16-16.5 is a nice all around number for a daily driver...

Rick
Old 10-16-2006, 09:56 PM
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Ive heard tuners say 18 on something at 300hp or so isnt a big deal. Has anyone here blown a HG at 18 degrees with a mildly modded truck?
Does higher timing move power towards the top of the rev range?
Old 10-16-2006, 10:28 PM
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I just took a 2700 + mile round trip hunting in wyoming and some of the fuel stations only carry the new ultra low sulfer diesel. my truck was loaded and got 19 mpg with the diesel no. 2 and got 14 mpg with the u.l.s.d. what fuel are you using? I bet thats it or a leaking return line
Old 10-16-2006, 11:52 PM
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Im willing to bet the tire pressures are down.I had reduced mileage a while ago.I was getting no better than 800 km per tank before the fuel light came on ,now i am over 1000.I discovered that the tires were at 60 psi and i aired them to 75 and voila.And they are supposed to be at 80 or so.Just recently i drove 2000 km in 2 days on 2 tanks.I also had 1000 lbs of tools and extra fuel on board.Airing up the tires produced results that were night and day
Old 10-17-2006, 12:31 AM
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Originally Posted by kawi600
Ive heard tuners say 18 on something at 300hp or so isnt a big deal. Has anyone here blown a HG at 18 degrees with a mildly modded truck?
Does higher timing move power towards the top of the rev range?
Maximum timing is different on 94 & 95 pumps versus 96-98 pumps. 94 & 95 can handle more timing without compromising the head gasket.

My timing was measured by injector pulse, not the traditional plunger lift. It started at 12° and was set to 20° as measured at the pump. We checked a 94 at pump versus injector and found a 4° difference.

I blew the head gasket with a #4 plate in stock position; a blocked wastegate that made upper 30's of boost; and dynoed at 300 hp.

I pulled out my dyno sheet when the timng was bumped. With stock plate and 3k GSK my max power was a 2,800 rpm before timing and 3,100 rpm after timing. I also gained about 20 peak hp.
Old 10-17-2006, 12:58 PM
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I had both low mileage and low power too. Turned out I had no boost due to a leak in the Waste gate actuator, no boost meant no fuel since the AFC reads boost to determine fueling.

You can kink the line that feeds the Waste Gate Actuator the turbo to test that theory. Also look for other boost robbers like leaks in manifold, intercooler, etc.

You may not be getting enough fuel for other reasons too, but I'm not sure if they would result in losing both power and fuel mileage.

My near identical truck went from 13--14mpg up to 21 (freeway).

Good luck.
Old 10-17-2006, 02:38 PM
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Originally Posted by huckstep
I had both low mileage and low power too. Turned out I had no boost due to a leak in the Waste gate actuator, no boost meant no fuel since the AFC reads boost to determine fueling.

You can kink the line that feeds the Waste Gate Actuator the turbo to test that theory. Also look for other boost robbers like leaks in manifold, intercooler, etc.

You may not be getting enough fuel for other reasons too, but I'm not sure if they would result in losing both power and fuel mileage.

My near identical truck went from 13--14mpg up to 21 (freeway).

Good luck.
I have my waste gate plugged too. I really need to replace my fuel lines and overflow valve. I decided to wait on the timing until I get my guages, they should be here thurs. The diesel I've been buying is from citgo, and it only says low sulfer, not for use in 2007 and newer engines. So I don't think it is ultra low.
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