Loss of power, again

[DuraDanMax]

Pardon me while I vent. 2003 6.6 DURAMAX NO MODS. A month ago had the power loss at 2,000RPMs. Truck just fell on its face. Code 087 I believe, 8 new injectors. While it was at the dealer, they mentioned a restriction in fuel from the tank. Have a Super Tank (62 gallon) tank, you can guess how thrilled they were to see I replaced the OEM. They wanted to remove the bed to clean the tank. Told them that it was not necessary, tank essentially comes out just as the OEM does. They said they would try blowing air back to the tank to dislodge what every may be causing the restriction, presumed to be at the screen at the sending unit. Was told they did that, paid $70 and was on my way.

One month later, and the truck had the same symptoms; fell on its face at 2K RPMs. Only this time quickly, within 3 miles, got worse until I could not keep it running at all. Replaced Fuel filter that had only been in less than a month. Also blow air back into the tank to make sure it was not plugged, all seem ok. Just to be safe, removed fuel in tank and replaced with new diesel. Was able to get fuel to the filter using the priming pump. Seemed to be suffering from fuel starvation. Had it towed back to the dealer. Tow truck operator mentioned that he could not hear the fuel pump initializing when we tried one last time to start the truck. Assuming that this engine has an electric fuel pump, it so can someone tell me where it is located? Temps have hovering around freezing for this period. Dealer has not had a chance to check for codes, but unlike last time the SES light did not come on. Cut the fuel filter open. There was a concentrated area of dark gray on one side of the filter about the size of your license. Air filter only 3 months old.

Checked the postings related to power loss, which date back to 2002, but could not pickup a pattern as to a common cause. Everything from fuel filter, bad fuel, injectors, air in the system, etc

[DmaxMaverick]

I don't want to get into all the possibilities, as the list could be rather extensive, so I'll throw in a simple thing to check.

When you installed your new tank, what hardware did you use? Did you use the OEM original plumbing? Or, did you use hose/barb type fittings? I've found that the hose/barb types, if not very carefully installed, can cut into the internal hose diameter, creating a "plug" in the line that can become tempermental. Your problem sounds like you are getting some restriction, somewhere, that reduces the effective usefulness of your filter. If the system already has a slight restriction, it would not take as much filter usage to cause enough restriction for the computer to see greater resistance, and set the code thinking it is plugged up.

Another simple possibility is the fuel cap. If it is not venting properly, too much vacuum in the tank will cavatate the pump, causing limp mode and setting the code.

Good luck!

[DuraDanMax]

Maverick,

Thanks for the suggestions. Used the OEM parts in the tank. Not sure I understand the issue of too much vacuum in the tank. Are you implying that the tank could be so tight that it restricts fuel from getting to the engine? What about the opposite, tank that cannot hold a vacuum, how would that manifest itself?

Dan

[DmaxMaverick]

A tank that holds vacuum will eventually starve the fuel suction pump, and set a code similar to that of a plugged filter. If your tank doesn't hold vacuum, for whatever reason, that will not be the problem. I'm just suggesting you might have a fuel restriction of some sort, whether it be a physical blockage (in the line or plugged filter), or vacuum preventing the suction pump from transfering fuel.

As you use fuel, the void in the tank needs to be compensated with air, or vacuum will occur.

[madmatt]

fuel in the oil? if so you may have a leak under the valve covers in the form of corroded fuel line sealing surfaces. I've seen similar cases and have replaced a couple sets of HP fuel lines because of this. thay don't leak nearly as bad as the injector failures but progressivly get worse.

[DmaxMaverick]

BTW:

Unless you've installed one, your truck doesn't have an electric fuel pump (missed that the first time around), or a lift pump, in the traditional sense, at all. The high pressure pump also has a built in low pressure suction pump that draws fuel from the tank. The entire fuel line is suction from the engine mounted pump to the tank.

[DuraDanMax]

Thanks to everyone for the education.

Fuel in the oil -- Not sure, will ask dealer to check and check myself once I get it back.

Now that I understand how the fuel system works, I have the following question. If I can pressurize the system with the primer pump, would that theoretically mean the primer pump should be able at a minimum to pull enough fuel for the engine to run? I ask, because that is the situation, the engine only stays running long enough to consume the fuel in the line / filter.

Truck went inside the dealer today, anticipate more information tomorrow.

[More Power]

Must have an airleak somewhere in the fuel lines. You could try pressurizing the fuel tank with 5-10 psi, then look for even a tiny leak in the fuel lines from the tank all the way to the injection pump.

MP

[DuraDanMax]

Wanted to wait some time before posting the status of my truck to have some level of confidence it is 100% fixed. Here is the story. According to dealer, who ever installed my after market fuel tank did not remove all of the packing (cardboard), and it was restricking the fuel from getting to the engine. Not sure I am buying that, but at the time I had no choice but to grin and bare it. Truck is running like it used to, better than it did following the injector replacements (which most likely did not need to be replaced), so they did something to correct the situation. Hope for the best.