Fuel tank coating breaking down? Other fuel tank questions

[65-f100]

OK guys - have a strange one. Here's the rundown on what happened. Trip to NC beach 2 weeks ago. Had about 1/4 tank left so I refueled before heading back to SC - about a 3.5-4.0 hr trip. Gas station is a high-volume station - not a truck stop - but not a mom and pop either. About 2.5-3 hrs into the trip noticed that the truck starting surging. Felt similar to a gasser with a plug wire going bad. Still had good power under load, but was bucking under constant throttle. First thought was bad fuel or water in the fuel. Made it home no problem but she was certainly not a happy camper. After getting home - cracked the drain valve and got a nice steady stream coming out.

Next morning drove it to work and seemed to be running better - barely bucking at all = thought maybe it just had some water in the fuel. The following day - back to bucking again.

Step1 - Decided to change the filter last night and bought some Iso Heet to put in the tank. After pulling the filter - decided to suck the fuel out and have a look in the filter housing. Bottom layer had a layer of orange brown crud as well as little shiny flakes all over. Pulled the housing and looked closer. Thought metal flakes at first but really looked more like a film. Decided to look a little further.

Step 2 - since my fuel gauge has been bouncing for a while - decided I would go ahead a break down and replace the sending unit. I figured it was due after 300K miles. I was thinking maybe the tank strainer had started breaking down and was disentegrating. Got the tank out tonight and pulled the sending unit. The fuel inside has a lot of material floating around in it - the same shiny looking stuff from the filter housing. Looking closer - it is some sort of coating on the inside of the tank that is breaking down. You can see areas of bare metal where it has come off. This has obviously been causing my drivability issues. Can certainly tell the strainer has material in it.

Just FYI - I do not use any additives other than a little 2-cycle oil for lubrication.

Now - I have several questions:

#1 - Are the factory tanks coated with something on the inside?

#2 - The fuel that I got in NC is very green in color. I know diesel fuel can vary in color - but this almost looks as green as antifreeze. Could this have caused the coating to break down?

#3 - What to do now? Replace the tank with a good used tank or buy an aftermarket new one? I've noticed the aftermarket ones from Dorman and Spectra both indicate they do not have baffles. How important is this on our trucks? Mine is my wife's daily driver - mainly kid transport with the occasional camper pull.

#4 - Can I clean the injectors by taking them apart? If so - preferred method? Should the nozzles be replaced? I am planning on replacing the complete filter housing and will flush and blow out all the lines before reassembly as well. May also replace the lift pump.

#5 - Do I need to be concerned with the IP? Anyway to flush it out?

Thanks in advance for any help / advice you can give.

Brad

[DmaxMaverick]

I'm not aware of any OEM tank coating.

Chances are, you got a large dose of biological contaminated fuel (algae), or a high(er) concentration of bioDiesel, which will let loose 300K miles of naturally occurring tank coating. What you describe sounds a lot like a #2 junkie getting off the stuff for bio. The filter should catch all that is harmful. Chances are, if the remainder of your fuel system is healthy, you were experiencing fuel starvation from the plugging filter.

[65-f100]

Thanks dmax for the input. I had thought about biodiesel as well. There appears to have been some type of coating whether it was factory or not. Any advice on cleaning vs replacing? I've heard radiator shops may could clean it. My concern is that I'll have the same issues if I don't get it all removed.

Thanks

[greatwhite]

I've read some anecdotal stuff about a "silvery" coating on OEM tanks but I can't confirm it either way.

The main filter is 2-5 microns, depending on which manufacturer you believe, so I wouldn't be too worried about the ip.

How many miles on your injectors? If you're up over 100,000 on the current set I'd just buy a new set for $500-ish and be done with it.

As to baffling, if you run the tank on the lower half of the gauge it becomes a concern with aerating the fuel and air entering the fuel system. Now, the filter manager is going to separate most of that anyways, but it's a concern.

[sctrailrider]

When I got my 91 a few years ago, I pulled the tank down when I replaced the IP & injectors just to clean it and be sure it was clean. I got all the fuel out and then put 5gl of gas in the tank and sloshed it around for a while. My tank was clean and didn't have anything in it, I couldn't tell if it had a coating on the inside, it didn't look like it to me. I would try and flush it out with gas or purple power or something that will cot the junk that may be built up on the inside of the tank.

I drive a fuel tanker here in SC and there is a lot of stores using bio fuel now, most of it is some really nasty stuff.... and good diesel fuel will be green for the ULSD, a problem with a lot of store tanks is that alge will grow in it and cause what you might be seeing.

Drop the tank flush it with something and filter the fuel before you pore it back in the tank and you should be good, when you have the tank down you can clean the sock or replace it if needed.

[65-f100]

Thanks for the input guys. I've already ordered a new Delco sending unit with new strainer so I should be good there. My concern with the tank is that I'm not sure that I will be able to get the rest of the coating off and may run into the same problem again. I was looking at the aftermarket tanks but the no-baffle concerns me. Going to try to find a good used tank locally. Checked with a couple of mechanic friends and they both confirmed that most tanks these days do have a coating of some sort on the inside. Did not know the ULSD was that green - thanks for the heads up on that.

Thinking I may just get all new fuel anyway just to be safe. Now what to do with 20+ gal of diesel. Bonfire anyone?

[convert2diesel]

I agree with the bio-diesel scenario. Spent a number of years playing around with the home brew stuff and filtering and water were always a concern. By definition, bio-diesel is part alcohol. It's chemical name is "FAME or FAEE". Fatty acid methyl ester when made with methanol or fatty acid ethyl ester when made with ethanol. As such it is anhydrous (soaks up water) and a solvent. If there is any crud in the fuel system it will disolve that and take it into the filters. Always kept a spare filter in the vehicle.

The coating in the tank could well be polymarization (s?) of the bio-diesel. This happens when bio-diesel is stored in a tank for protracted periods of time. Essentially it creates a bio based plastic that tends to migrate onto the inner surface of the tanks its in. Allow it to mix with algea and you have a real dogs breakfast in there.

If your using B20 that is available commercially, don't assume that it's fine. While the rules and regulations exist as to product quality and water retention, the policing of these rules has been less than stellar. Commercial bio-diesel quality is still all over the map. Actually preferred my home brew over the commercial stuff. At least I knew what went in there and did my own testing.

Just have your local guy steam clean the tank and flush out the fuel system and your good to go. Use biocides if you live in a warmer climate to keep the algae at bay and don't let even B20 sit in your tank for more than a month.

Bill

[65-f100]

Bill - great info. Thanks! Sounds like exactly what happened. The "coating" looks almost like a thin layer of "plastic" that was sprayed on. My guess is that my last fill up must have had algae in it like you describe.

I do live in SC so very hot and humid - do you have a recommended biocide?

Also - would you strain and re-use the fuel I pumped out or just start with new?

Thanks!

[convert2diesel]

Any of the biocides will work equally as well. Algae lives in the transition layer between settled water and the fuel. Takes it nutrients from the fuel and its oxygen from the water. Only really a concern with static storage tanks, or tanks with lots of water in them such as marine tanks.

Not normally an issue with in-vehicle tanks that are driven daily as the fuel is replaced often and the fuel is sloshing around. Doesn't give the bugs any time to breed. They lead a very sedentary existance. You only need to treat if the truck is stopped or stored for awhile. I would think that in your climate, the supplier should be dosing his fuel with biocide already.

If you picked up some algae than it probably came from the in ground tanks at the filling station. More than likely you got a load from the bottom of the tank and the operators didn't keep up with his dipping regime. Should be done daily to indicate any water build up.

Straining and filtering the existing fuel is just not worth the chance. If in deed there is algae in it, all you'll do is introduce bugs into the next fill-up. These single cell creatures are invasive.

Bill

[65-f100]

Thanks for all the input. Found a good used tank locally for $100. Rinsed it out, blew out all the lines, new sending unit, and new filter assembly. Fired it up and is running great - smoother than it has in a while.

Really appreciate this forum and all the advice!