Possible condensate in the fuel - PeachParts Mercedes-Benz Forum

Lycoming-8 · #1 11-02-2015, 01:48 AM

This is a follow-on thread to a previous one about an auxilixry fuel tank under the hood. The under-hood tank installation worked well after replacing the leaking primer pump with a newer black push style, and got me and the car home from the outdoor re-work location.

Now I am in need of advice on how to determine if there actually is water contamination of the main fuel supply and how to remedy the situation. Is the best route to flow the remaining fuel in the tank to a can or other container? Then check the contents of the external can or container for water. Or do I need to use some chemical means to tie up the water, assuming that there is an appreciable amount? Know this works for gasoline, but what about diesel??

I know that water going thru the injection pump is a real No No, because of the corrosion potential, and that was the reason for the original exercise. However, I can't drive on this 96oz under-the-hood container forever, so need to see some quality advice like the last thread.

This is on the '83 300D, and Thanks in advance.

mannys9130 · #2 11-02-2015, 02:03 AM

If you suspect you have water in the tank, my opinion is that you'll need to pull the tank and thoroughly clean and dry it. Yes, they make fuel drier for diesels but it's still going to emulsify the water and bring it into the IP. That's a very very bad thing, so I think pulling the tank is the best bet. You'll not need to worry about the tank having crap in it or the tank strainer being clogged.

I'd think it'd be a good idea on any of these cars.

Once you get the tank cleaned, dried, and reinstalled, change your spin on filter because it functions as a water trap as well as a filter. Then you'll be in business.

Lycoming-8 · #3 11-03-2015, 01:29 AM

mannys9130,

Thanks for your quick reply. Do you have any suggestions for verifying wether or not there actually is water in the tank. I agree that the tank removal and cleaning would likely be the best way to eliminate it. However right now I am not really sure there is a significant quantity of water in the tank, and would hate to go thru all of that, to then find no significant water.

mannys9130 · #4 11-03-2015, 02:17 AM

All I can think of is to remove the fuel level sender and suck the liquid at the lowest point of the tank into a container and see if you have little balls of water amongst the diesel. There's almost a 100% chance that you have water on the bottom of the tank. After 30 years of pumping fuel, you'll get a little blob here and there as well as condensation. It becomes a problem when it gets high enough to be picked up through the strainer and causes the fuel lines to freeze.

So I'd try the tank biopsy and see what you suction off the bottom.

Lycoming-8 · #5 11-03-2015, 11:35 AM

mannys9130,

Thanks for the suggestion. Will give that a try, and see if there really is a serious water problem. Hopefully it won't prove to be a terribly messy job.

mach4 · #6 11-03-2015, 12:27 PM

Not necessarily recommending this as a solution, but something worthy of consideration is a water separator, maybe something like this -

The advantage to this idea is to verify that you actually have a water problem without having to pull/drain the tank. If you do, then you can pull the tank to fix, and if not, you've got insurance against a future contmination.

It probably makes sense to encourage a strategy of prevention, specifically buying diesel only at name brand, high volume stations where the fuel is always fresh.... and try to put on lots of miles to keep the fuel from getting stale in your tank. I follow this strategy and have 90k miles on my main fuel filter with no measurable drop in pressure - yes I monitor fuel pressure continuously.

Lycoming-8 · #7 11-04-2015, 01:56 AM

mach4,

The water seperator idea is an interesting one, will have to look into that, especially for the long term. The concern for water came about because the car sat for several years, not because I did not follow your fuel purchase suggestions. However thank you for raising those issues, as others may not be as picky as I am about fuel.

vstech · #8 11-04-2015, 07:28 AM

Well... I actually pumped water into my fuel tank accidentally one time... It had my truck stranded for months... I ended up draining the tank repeatedly, and installing a HUGE fuel filter with a clear drain hose to see ANY water buildup in there...

OM617YOTA · #9 11-04-2015, 08:23 PM

Change your secondary filter. Tip your old filter over into a clear jar and see what comes out. The stock filters aren't water blocking, but there's a small settlement area in the bottom that should collect something. This is also likely a one-way solution - presence of water is obviously conclusive, absence may not mean anything at all.

I'm all about additional filtration - that one that Mach4 linked looks like a good option. I added a Griffin version of the Racor 500 with water blocking 30 micron element and large sediment bowl as a primary filter, and am in the process of adapting the stock fuel filter housing to hold a CAT 1R-0750 2 micron filter for secondary. A water-in-fuel sensor is on the list as well.