Newbie Diesel Questions

dpkimmel2001 · December 15, 2008

New to diesel with a few of questions. Sorry if this is the wrong category to post these under.

Why are there two batteries?

The manual states that at some point the message center will indicate that I will have to change the fuel filter. The bleeding of the air concerns me. Is it something I should have done at the dealer or is it not really all that difficult of a procedure when following the instructions?

The last question that I have is on water in the fuel system. This isn't a common thing, is it? The manual mentions how to drain the water from the fuel system and I can't help but wonder if all you you have encountered this or is this extremely rare?

Thanks for any response!

merlin5577 · December 18, 2008

New to diesel with a few of questions. Sorry if this is the wrong category to post these under.

Why are there two batteries?

There are numerous reasons, biggest one being the draw on the starter motor when starting the engine.

The manual states that at some point the message center will indicate that I will have to change the fuel filter. The bleeding of the air concerns me. Is it something I should have done at the dealer or is it not really all that difficult of a procedure when following the instructions?

Changing the fuel filter is a breaze. It is similar to changing the oil filter but it has a water sensor in the bottom. It takes about 10 minutes with a good oil filter wrench. I pre fill the new filter with diesel before installing it and have never had to bleed any air out.

The last question that I have is on water in the fuel system. This isn't a common thing, is it? The manual mentions how to drain the water from the fuel system and I can't help but wonder if all you you have encountered this or is this extremely rare?

I have had my 03' for almost 2 years. I check the filter when I change them and randomly crack open the bleed valve and have never once had water come out. It is pretty rare, but it can happen.

Thanks for any response!

Welcome to the site!

masterjc · March 25, 2009

from what i understand the most common way to get water in the fuel is from the gas stations, usually when their running low on diesel and its sucking all the crap out the bottom of the tank.

pwall · March 25, 2009

Two batteries....needs lots of power to turn the diesel over. ;)

Regarding your fuel filter, the DIC will tell you how much life expectancy is left in the filter, assuming your truck has the DIC on the dash (if not, cheap and easy upgrade...run a search on this forum, lots of topics on this).

Water in the fuel...I agree with masteric's post above.

petep1 · May 21, 2009

Prefilling with diesel is not a good thing. Unfiltered fuel is getting by the filter that way and injectors do not like that. Very expensive to fix. Just do it the way the book says and pump it through. I remove the top plastic holders from the fender, pull it down some and you can get to the filter and connector and it makes it a lot easier to work.

paulzar396 · May 21, 2009

Prefilling with diesel is not a good thing. Unfiltered fuel is getting by the filter that way and injectors do not like that. Very expensive to fix. Just do it the way the book says and pump it through. I remove the top plastic holders from the fender, pull it down some and you can get to the filter and connector and it makes it a lot easier to work.

Good questions and great response. I am a diesel newbie as well and learned a good deal from this thread!

Silverado4x4 · May 21, 2009

Alot of the fuel depends on diesel you get in your area, stay away from the small mom and pop stations and stick with a station that turnsover alot of fuel. Diesel fuel that sits to long can get algae in it with water also. As far as the fuel filter its a easy change but you have to make sure you get a good seat on the O- ring if not you will stuck air into the system and thats a whole nother problem. If your un easy about it then let the dealer or a shop that does diesels do the filter changes which will be around 7000 to 15,000 miles max on a filter but that depends on the fuel your getting. If you change the filter yourself once you get the filter on loosen the air bleeder valve and start pumping the primmer bulb till fuel comes out on the bleeder valve then tighen the valve but be careful not to over tighten the air bleeder cap as it plastic and can snap off real easy.

nc6600 · May 24, 2009

Alot of the fuel depends on diesel you get in your area, stay away from the small mom and pop stations and stick with a station that turnsover alot of fuel. Diesel fuel that sits to long can get algae in it with water also. As far as the fuel filter its a easy change but you have to make sure you get a good seat on the O- ring if not you will stuck air into the system and thats a whole nother problem. If your un easy about it then let the dealer or a shop that does diesels do the filter changes which will be around 7000 to 15,000 miles max on a filter but that depends on the fuel your getting. If you change the filter yourself once you get the filter on loosen the air bleeder valve and start pumping the primmer bulb till fuel comes out on the bleeder valve then tighen the valve but be careful not to over tighten the air bleeder cap as it plastic and can snap off real easy.

If you have a truck stop in your area go there to get your diesel. Also look on the ground by the pump, there is usually a puddle on the ground. The bigger the puddle the more trucks filling up which is good. also if you see a tanker with the hose in the ground filling up dont get diesel there for a little while.

Shawn T · August 25, 2009

The DIC is based strictly based on mileage. It just tells you to change it every 15000 miles and you reset it when you change it, and so on. I have had a filter clog on me at about 7000 miles. The first indication you will get of a dirty filter is sluggish acceleration. The most prominant indication your filter is plugging is the shifting behavior of the allison. If it seems to "jump" into the middle gears and hover there it probably means your ready for a filter change.

1. remove intake pipe between air filter and intake

2. remove oil dipstick (it gives you that extra inch of room to remove fuel filter and I;ve heard of people snapping the yellow ring off)

3. Unplug wiring harness attached to filter. It has a 3" pigtail and is easy to reach

4. Use a large filter wrench to remove old filter and try to keep upright, not to spill all of the fuel out

5. fish filter out and remove the nylon nut attached to the bottom with the "water in fuel" float.

6. Attach sensor to new filter with new O ring and remember to attach new O ring to top of filter.

7. Install new filter in reverse order and crack the bleeder.

8. Pump plunger until bubble free fuel flows, close bleeder and crank the motor.

Hints: Get a filter wrench, makes it much easier. Be carefull changing sensor, the nut is made of soft nylon and can easily strip. Make sure O ring on top of filter is seated while tightening, it tends to come out of the groove easily. Don't overtighten and squash the O ring. After bleeding and during cranking: Crank motor continuously for about 10 seconds. It may take about 5 seconds to start, if it takes longer that 10, there is still air in the line, need to bleed again.

I've owned 2 duramaxes and changed about 6 or 7 filters and this is just from my trial and error on what works best for me.