I cleaned my fuel system, replaced the hoses and filters. Before that my fuel was a dark blue and kinda dark gray. I found a silvery paste in my tank when I cleaned it which I'm still clueless about after asking this forum. After that I put clean diesel in and it showed a clear yellow color in my primary filter. Great.

Well now my fuel is slowly beginning to turn into a blue color and constantly getting dark, turning back into the old color of diesel that I had. Does anyone know what's going on??

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1983 300D turbo diesel

shot in the dark, but it could be that someone used a tank lining product that is now coming off?

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2004 VW TDI with lots of mods
1991 350SDL with a clean body and a bunch of miles.
1987 300D for parts (cracked head, bad trans)

i've seen that silvery paste in high mileage gasoline gas tanks before; i came to the conclusion (might not be correct) that the paste is from the gas pump nozzles; every time you put the nozzle in the filler hole there are some flakes (silver metal) coming off the nozzle and over time they accumulate in the bottom of the tank. since they're always suspended in gasoline (or diesel) it kinda makes that silver paste.

I'd say the blue or dark gray would be a fungus issue. Have you dumped biobor or startron in there at all? Can't hurt to give it a try and it'll kill whatever is in there anyways.

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TC

X2
You have an infection.
Post again when you have treated it !

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Grumpy Old Diesel Owners Club group maintainer/member

"Life is tough..it's even tougher if you're stupid." John Wayne

I no longer question authority, I annoy authority. More effect, less effort....






1980 300D now parts car 800k miles
1984 300D 400k miles
1987 250td 90k miles English import
2001 jeep turbo diesel

other toys ~J.D.,Cat & GM ~ mainly earth moving

I'm not sure you have an issue. Road diesel is dyed blue and off road diesel is dyed red so I'm thinking you may be fine. A photo of your prefilter might help. A few little black specks is normal, but if it's filling up the filter then you've got fungus issues.

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The primer pump could also be leaking engine oil into the fuel system, turning the fuel blackish.

I guess I'll get some startron just in case

There is nothing collecting in my filter that's why I didn't think it was a fungus thing.

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1983 300D turbo diesel

try some studjuice?

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85 300D turbo pristine w 157k
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parts for sale- pm me your needs.

a fungus among us? startron is the cheapest and easiest thing to try. fyi my diesel fuel as viewed through a transparent pre-filter is a golden color. i've never seen red, blue, green, or any other colors.

That is Close; it is the little O-ring in the Fuel Supply/Lift Pump that goes bad. When that happens some Members have had the Oil inside of the Fuel Injection Pump get sucked into and mixed with the Fuel inside of the Fuel Supply/Lift Pump.

If your Injector Nozzles are extremely worn or the Spring inside is broken (that would cause a miss) it is also possible for combustion gasses to get into the returning Fuel.

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84 300D, 82 Volvo 244Gl Diesel

I've seen it greenish (sort of like mountain dew) but I think that was due to the winter additive. The only time is has actually been dark was when I had some fungus in the tank. Startron took care of it immediately.

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TC

You know what oil sounds about right. When I changed my last filter it had a thin black coating on it. So did the tank strainer. No clumps at all, and the holes weren't clogged, just a thin black film. Do you know the part number for that?

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1983 300D turbo diesel

made me laugh. I've been working with commercial generators for lots longer than I have been playing with 123s. First time I saw the fuel filter in my 123 with the amber fuel I had to stop and think why the fuel was a funny color. I'm used to seeing red fuel in the gen sets....

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1998 E300D (wife's DD)
1987 300TD (17 yo son's DD)
1983 240D (sold to greazzer)

2004 Honda CR-V (mine)
Guess who's next for a mb?

2-stroke oil turns fuel blue and other fuel additives. Otherwise, straight diesel is yellow.

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85SD 240K & stopped counting. Looking for all 3 grey seats to go in my SD (anything from a 126).