Keep getting water in fuel

Hello.... Thank you in advance for any replies! I have a '96 Volvo WIA6 with a N14 red head. We use it to haul hay on a flatbed cross country. Here's the MAIN problem: We keep getting water in the fuel! Our last two trips out, once the tanks got down to around 50/60 gal. ea. the check engine light would come on, flash, and then the engine would start surging. Everytime we drained the filter, there would be water in it. The first trip, the truck had sat through some serious downpours. After this trip, we drained the tanks, and put clean diesel in. Truck operated just fine, test drove about 50 miles, and then went to a different station to fill up, just to be safe. Left out again with no problems, until we got half way to unload. At the half way mark it started to sprinkle, so we had to pull over to keep the hay dry. (My tarp had been destroyed, not a stroy thats realvent) Rain cleared we started back out. (Btw truck was sticking out in the rain, shelter wasn't big enough for truck and trailer.) Overnight, engine cut out 1 time, stoped early in the morning to sleep. When we got up there was a heavy fog, pushed on, unloaded, headed home. Just before we left for home, it started to down pour again, and rained off and on on the trip home. Again once the fuel level got to the magic point surging returned worse than the teip before. We have not had this problem in the past, have had the truck for several months, and have made several trips. (Including trips where we got rained on) Looking for any and all possibilities. Not seeing any cracks in tanks. Also, on the trip before this started, we lost just a little tread off our right steer, never paid attention before, but there is a breather line hanging from the top of our left tank, which comes out of a brass fitting. This line is missing on the right side, and hole in fitting is pointed toward front of truck. Inside diameter of hose is: 5/16 we have replaced it just incase. Tell me what you think. Is there any other way water could get into fuel tanks?

 

**UPDATE** Just finished draining tanks, did not find any water. Also pulled vacuum on the fuel line that runs through the block to preheat fuel, and it held. If it were condensation there would be water in the tank still, wouldn't there? Still looking for ideas. Is it possible there was water in the line somewhere? The only thing that makes me dismiss that idea is it ran fine on 50 gallon of fuel total when we test drove, and ran fine for an additional 600 miles after we filled up. It wasn't until after we unloaded and started back there was a problem. On the way back the problem got progressively worse. We started out having to drain filter every 100-200 miles, until the last 150 or so, then draining the filter did nothing. By the way, at this point Iit was around 2:00 in the morning. Once draining filter didn't help, we tried putting additive in. Condensation is one of my thoughts, but why is there no water in the tank this time? Also, this is a change, there was water in the tank the first time. Thanks again for any help.

 

We haven't ran the truck through any standing water recently, to the best of my knowledge. I am wondering if there is anyway we could get water in the fuel through the return lines. I an thinks about pulling a vacuum on the return line coming frim the head, if I were ti do this is there any possibility of causing damage in the engine? Keep the ideas coming, I am trying everything right now, even suggestions I don't think are the cause! Thanks again for any and all help so far and to come!

 

Sorry, I am a novice, but fortunately common sense will get you a long way in life. With that being said, I believe I have the "spin on" type, we don't have to remove anything to change the filter, and it just "spins on". The inlet line does go through the water jacket just before the filter. Which type does this sound like to you? If I haven't given enough information, what would a heated set-up look like? Thanks for the suggestion dirthaller!

 

Quick update for those trying to help.... Still having problems! It isn't cutting out quite as much, I put a fuel filter on that we had cleaned out with diesel 911 over a week ago, right before we put it on, we dumped some fuel in it, poured it out, no water. When we started the truck, it still cuts out from time to time. We opened the pittcock a few times, but didn't get ANY water until the truck had ran for an hour, hour and a half... then it was very little. The head gasket has a middle and rear head gasket have small leaks, just enough that water will bubble out the side (one bubble every 2-3 minutes). The nearest place to get a filter in stock is 2hrs round trip. My parts house ordered one for me, it will be here in a couple houts. Keep the ideas coming boys! We are baffled!