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Discussion Starter #1
I think I am experiencing poor fuel mileage. From what I am reading, I should be getting around 18 MPG, but I am getting closer to 10-11 MPG. I just replaced the IP. I do have 245,000 miles - but the truck runs great. Is there anything that would cause bad fuel mileage? I cant see anything else effecting this.
 

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Ya, 10-11 mpg's is gay.

There are lots of things. Injectors, tire pressure, maintanance items, tranny condition and lockup, fuel quality, style of driving, etc, etc.

Just tackle and test one thing at a time.....245,000 kinda raises a brow....have you done a compression or leakdown test?

If it poor MPG's started suddenly after IP replacement, I would investigate in that area first....where did the pump come from?

Good luck.
 

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Discussion Starter #3
Well I bought the truck about a month ago and it needed a pump, so I dont know what the MPG was before. The IP is a rebuilt from a certified rebuilder. Tranny is fine, as are tire pressures. How would injectors effect MPG?
 

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Injectors, yes.

Timing chain set, yes.

Air filter, yes.
 

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What did you do to reset the pump for the TDC offset?
 

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Not to say this well increase your MPG from 10-11 to 18MPG, but it sure isn't going to hurt...If I don't keep the fuel filter changed every 10-12,000 mile I'll lose 1-2 MPG. Since you just change the IP I'm guessing you changed the filter too? If not it would be a good thing to do. If your not using a additve you should start doing that as well it tends to help MPG aswell. I use Power Service in the White bottle, but Lucas makes a good one aswell. BTW the only diiference between Power service White or Grey that I know is the white bottle has Anti-gel and grey bottle doesn't.
 

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Discussion Starter #7
Lets see. Yes I replaced the fuel filter. I used a Tech II to do the TDC offset. I am wondering, how exactly can the injectors or timing chain effect mileage?
 

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If the timing chain is original, it likely has way too much slack to keep the IP in time properly. The injectors are known to be good for somewhere between 100-150,000 miles, and as I understand it, start to leak fuel and/or not atomize the fuel properly for good combustion.
 

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BTW, dumb question, but are you sure the speedometer/odometer is correct? No other problems with the engine- EGR, vacuum system, air filter? How about the drive train and brakes? Dragging rear brakes could hurt fuel mileage, and an automatic transmission with issues could do the same.
 

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Less power the engine makes, the more the driver mashes the accel pedal to keep up - bad fuel mileage.

Loose chain, worn sprockets = retarded camshaft timing = retarded inj pump timing = low power.

Poor injector spray pattern + altered injection pressure = low power.
 

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Discussion Starter #11
I will need to check the chain and the injectors. I compared to a 2000 with 65k miles and the power feels to be about the same, but I will check these things. I think I can hear the timing chain slapping around a little around 1700 RPM, so that might be my first thing to check. However, when I look at the specs for the injector pump, the actual and desired timing are right on the money.
 

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Won''t see it there, my man - only comparing that to a static timing device will show the degree of retardation.

PCM does it's own compensating act.
 

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Discussion Starter #13
I am now wondering if it could be leaky injectors. When I first start the truck after it sits a while, i get 1 small puff of black smoke, but I am not sure if leaky injectors would cause that. New to diesel :) Other than that it runs perfectly though. Idle is dead on acurate.
 

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has anybody noticed a mpg improvement running the gear drive instead of chain?
 

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good question. Mine needs to be replaced soon (300k) I would like to hear from folks that have tried it.
 

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Folks who replace worn with a new chain set report a very noticeable improvement.

Folks who replace worn with the gear set report a very noticeable improvement.

The only viable test to prove any difference would be to replace the timing chainset, drive it a few months noting the tremendous improvement over the worn chainset, then install the DSG, drive it a few months, noting any differences.

The really big advantage to the gearset is no more timing train deterioration - period.

And the noises comng outta the oil fill tube are a lot less scary.

.
 

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Discussion Starter #17
since i dont feel like doing this timing chain on my own, how much should i expect to pay for labor?
 

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How much $$$?

No idea, but suffice to say several hundred times more than you will ever recover in fuel savings.

There is a certain amount of slack allowed in the timing chain, about a half inch I think in a new chain, to 8/10ths in a worn chain, or in that general area.

There is probably a way to test the degrees of movement back and forth and convert that into chain slack, without exposing the chain. I would figure out a way, rather than to pay someone to replace the timing set.

Throughout this thread, there has probably not been sufficient mention made of driving habits.

Probably the single biggest fuel consumer of all.

Presuming, as you say that the engine appears running fine, I would leave the thing alone, and concentrate on driving style for fuel economy.

If you have calculated your mileage in stop and go city traffic, with long warm ups and extended idling, your mileage is not worth calculating, whatever you do get will be a disappointment.

Your best mileage in a 6.5 will be long trips on relatively flat terrain, and at around 1800 RPM.

With your 3:73 gears, that's around 55 - 60 MPH, or so.

Stop and go driving kills mileage, any amount of RPM above 1800 kills mileage, timing sets, injectors and the like are expensive, and to have installed at a dealership is downright prohibitive, at least to me.

If you are hell bent to change them, and have a set of wrenches, wait until you have the time, and with all the expertise in this joint, you can pretty much replace / repair anything on your truck.

I'm just a little worried that after you spend a grand on a new timing set, you may not see any difference in mileage if your driving habits aren't conducive to good mileage.
 

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Time chain I think runs about 6-8 hours labor. To get to the timing chain you have to remove the water pump, it would cost no additional labor to change the pump. It wpuld really suck to have to replace the pump this summer after doing the timing chain. For my money your on the last half of your engines life I would not put a gear drive in UNLESS you plan on keeping the truck along time and rebuilding the engine when the time comes. The gear drive cost about $200 (us) more than a chain and gears, I would rather put $100 of that in the water pump. These engines can last from 300K-400K miles.

Another item that can affect MPG is the SOOT trap (cat) they get plugged up and increase back pressure. Folks who have, replaced, "removed" (for test & off road purposes) or gutted the cat have reported increased mileage after doing so. IMHO with 245K miles on the truck Injectors, timing set and soot trap need attention, I would bet with those don you would get 17-19 mpg at 65-70 mph empty.

Regarding injectors, I replaced mine and timing chain at 158K miles. The vendor I got the injectors from had (now closed locally) test bench for injectors and pumps. Since I bought new injectors from them they tested my old ones for free and out of 8 only 3 had a "good" spray pattern, the other 5 pissed a stream, and I use fuel additive every fillup. My mpg had been slowly declining and it jumped back up 3 mpg after changing timing set and injectors.
 
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