Originally Posted by ExcursionDiesel
The trick is to not refill until as near empty as possible. This reduces mixing of old and new fuel. But yes, I'm expecting 3 to 4 tanks minimum if I can run it low enough each time.
Does anyone know if running our VMs bone dry creates a hard start situation? I know the old mechanically injected diesels require bleeding if run dry. It seems a common rail would pickup new fuel and reprime without issue. I'm thinking about siphoning my tank as low as possible, grab a 5 gal can of clean diesel then run it until it quits, refuel from the can and drive to a service station to refill. I can burn the old dyed fuel in my tractor.
Draining the tank and immediately replacing with new fuel won't cause a hard start situation, as long as you don't dry crank the engine. I've removed the fuel tank on my 05 CRD Jeep VM diesel, drained the lines, added an in tank lift pump, added fuel, primed the lines, then restarted and it fired up instantly. No injector bleeding at all, just key on a couple of times prior to starting it to fill the fuel filter.
Just avoid dry cranking it.
That's bad for both the electric lift pump in the tank and the aluminum Bosch CP4.2 HPFP. They both depend on the fuel for their lubrication and cooling. If they're activated without fuel long enough, it can cause far more serious issues than just a hard start.
There have been a few issues with the CP4.2 aluminum HPFP's failing due to low fuel lubricity and contamination, re VW TDI CR Jetta's as well as Ford and GM trucks using the CP4.2 with contaminated fuel. You certainly don't want to do anything that increases your odds of a dry start or increased moisture in the fuel.
Running your tank low during normal driving increases the chance of the ULSD absorbing more moisture from the air than it would with a full tank, as it's more hygroscopic than the old low sulfur diesel fuel. You probably already know that as long as you've been driving diesels.
Honestly, I think you may be a bit too anxious over the dyed fuel. As long as it's ULSD and clean, you're fine mechanically. Legally, if your documentation is good, you have nothing to worry about. Companies that make Red Solvent 164 advertise its detection at dilution ratios of 1 to 20,000. That's about 16/100 of an ounce on a 26 gallon tank, so you're not going to be rid of it at detectable levels any time soon. That much will be on the inside of the in tank lift pump. Even if you removed the tank, wiped it dry and clean, filled it full of new fuel, the dyed fuel is still in the lines, filter, injectors and HPFP - As soon as you crank it up, they'll return some fuel to the tank and you're going to be right back to enough to meet the 1 part in 20,000 for detection. Detection at those levels isn't by color, it's electronic and it's used by the fuel industry for marking fuel for theft identification. If they have them, the fuel dippers probably do also.
You many also find draining the tank a bit more work than just siphoning it out. Jeep has been using something in the fuel filler line and tanks since at least 2005 that prevents a normal siphon hose from being used, at least on some of their models. I tried to siphon D2 out of mine (Liberty CRD VM diesel) back in 2005 and the hose simply could not reach the fuel tank.
If you're determined to drain the tank, you might want to check out an electric fuel drain pump from somewhere like Northern Tools and try to see if some small diameter plastic tubing will reach the bottom of your fuel tank.