Water in Fuel

[mark2line]

I have a 2008 Gulf Stream Tour Master on a 2007 Freightliner chassie with a 330 Mercedes diesel. I have 6,500 miles on it. On my way back from Florida back in Janurary I had an alert come on the dash that said water in fuel. I purchased an additive that said it would remove any water. After I added this to the fuel it seemed that the alert went away. We had traveled about 500 Miles and again it seemed to go away. We went camping to a local camp ground about 30 miles away a couple of weeks ago and the warning came on again. Has any one had this problem. The engine seems to be running OK. Should I get it checked out at Freightliner. Should I try a new additive.
I am planning on a trip across the country next month and do not want to have any problems.
Thank You,

mark2line

[GaryKD]

Hi mark2line,
Does your fuel system, have a water/fuel separator? If would be a canister type device with a wire or two coming out of the bottom. If so, there should be a way to drain the water from the separator. It should be no more than a quart of fuel/water. There is also a maintenance schedule when this separator should be replaced. Consider replacing it during the annual maintenance of the oil and fuel filters.

The reason I mention this is the signal for water in the fuel (on my coach) comes from the sensor in the bottom of my fuel/water separator.

[mark2line]

I had the filter replaced this past december when I had the oil changed.
I will check to see if I can find what you are talking about

mark2line

[TXiceman]

I personally feel it is a good idea to carry a spare fuel filter on any diesel and replace it as soon as possible after you have a water in fuel light.

Ken

[RustyJC]

I don't know about the Mercedes, but Cummins includes a drain on the fuel filter/separator to drain any water that you may pick up through condensation or with a bad batch of fuel. As sensitive as diesels are to water, I can't imagine that Mercedes wouldn't have a similar provision. What does the Mercedes engine manual say?

Rusty

[RVDude]

Don't use additive, change the fuel filter(s). The filter(s) have water traps in them, you do NOT ever want to drag the water into a diesel engine by using an additive. Water, no matter how slight, in a diesel injector can cause serious damage. That's why the fuel filter(s) have built-in water traps - so the water never gets to the engine. Get the filter(s) changed ASAP. Since you have a water light, there is a water/fuel separator somewhere in the fuel line be it part of a filter assembly or a separate device. You'll need to find it and drain it as well.

[mark2line]

Thanks to all that replied. I am going to take my coach to have it looked at and serviced. I will also get an extra fuel filter to take with me just in case.
Again thank you to all that replied.

mark2line

[nsdienes]

We had the same problem on our maiden trip in our 09 Meridian. Bottom line, a little water got into the fuel at a less than prime truck stop. Every time the RV would tilt left or right, the warning came on. One parked, and once entering a driveway. According to Freightliner, the shaking moved the water over the sensor in the trap. Gave the drain a brief opening to let out a few drops and the problem went away.

Nick Dienes

[Gary RVRoamer]

The fuel system is supplied by Freightliner, not the Mercedes diesel. I've never seen a Freightliner without a water separator and am sure mark2line has one as well.

The separator needs to be drained of water. If the problem recurs, change the separator/filter. If it still persists, there must be a lot of water in the fuel tank and it may take a lot of fuel additive to remove it or may even require draining the tank. His problem doesn't sound anywhere near that bad, though.

[mark2line]

I took my coach to New England Detroit Diesel and they found that there was not any water in the fuel. They told me that it probably was a defective sending unit. They could not find any numbers on the sending unit and did not have one in stock. I called a local parts place and they had what they think is the correct part. Being that it is an electrical part they will not let me return it if it is the wrong part. I asked if this was a warrante item and was told that electrical parts were warrenteed for 12 months. Is that true. Anyone have any knowlodge if this is so.

mark2line

[EngineerMike]

My guess is the sending unit did its job and is working, and the water quantity was minimal & has now been passed thru the engine. If the tech tested the sender and has a basis for his statement, then I'd believe him.
When I had a 6.5 liter GM diesel, it had a water sensor at the base of the filter/separator but no drain. I got water in fuel from a Flying J that had snow on the ground and probably got some runoff into the tank fill or else got condensate. I used a quart of additive and the problem disappeared in a few miles and never returned.
Usually the quantity of water is minimal, and if you have a drain it is better to drain water till you get clean fuel & recheck again after a few miles to get a handle on the situation. If you get still more water you know you need to monitor it closely. If it is only a few drops then additive is a good solution IMO. You probably have a small amount in the tank that will get picked up from time to time, and the additive will eliminate that by incorporating it into the fuel & passing it thru the engine. You get a teeny boost from the steam that you will not notice, then it is gone. Additive is best if added to a tank you are about to use entirely and then fill up again, and IIWM- I'd use additive in the next tank also.
If you tap the drain and there is a lot of water, you need to get the situation remedied, as additive won't cure a large quantity of water in the tank, and you could damage your engine if you try. For this or algae, the tank needs to be drained & cleaned and filters changed till they don't get fouled (i.e. open the filters to check). A nasty process that hopefully won't happen to me or you.