Need help with strange fuel problem

I have an M35A3. There is a brass check valve at the fuel tank which is giving me fits. If truck sits for any length of time, the brass check valve develops a green sticky coating which prevents the value from opening thereby starving the engine of fuel. I have to disconnect the fuel line and remove the check valve from the tank, soak it with various items until it frees itself up again, then reinstall it. After that it runs fine until it is parked for a few days/weeks, then the process has to be repeated. So - any thoughts on what causing the brass check valve to gum up with a green coating? Anyone run into this problem and what did you do to solve it?

pbranch since this is an A3 you are running straight diesel fuel correct, no strange additives or anything? Your issue is rather odd because it sounds like your check valve is reacting to something in your fuel to develop this sticky green substance. The truck is running fine? Have you ever had your fuel tank and lines cleaned? Not that they are dirty but is there something in the system causing this reaction? How long is "any length of time" is it a day, a week or a month? Is the truck sitting out in the elements or is it under cover?
A little more info Pbranch and we may at least begin to narrow this down for you.
Karl

Whats your fuel tank look like? Shine a GOOD flashlight down into it. Look all around. Drain some fuel out, but from the BOTTOM of the tank. Look at the fuel. Perhaps use compressed air, and blow back into the fuel tank, at the check valve, (remove it and open the fuel tank cap). Thats a good place to start.

You might want to read through these threads.

[h=1]Problematic M35A3 Fuel Tank Check Valve[/h]
[h=1]M35A3 - No Start - Lost Prime[/h]

Disconnect your supply line, keep it upright and cap.
drain your tank( it’s a pain in the wallet) pressure
wash the tank. Adjust the pickup tube while your
there
fill, then reconnect supply line, and fire up.
have done it to several “A3s” never had to bleed
injectors. and in colder climates add 10% gasoline
to your fuel to help it run better and the gas
also kills the diesel type “algae”.

To reply to Karl: The tank and lines have never been cleaned that I know of. The truck sat for quite some time before I aquired it. Have added fresh fuel since then but never really emptied the tank. Once started the truck seems to run fine but "greens up" in as little as one day. I have added some additive that is supposed to killl green algie but didn't seem to do any good. The truck is parked outside and has always been. Any thoughts?

that used to happen on diesel boats, like Sue said....its diesel algae and theres a good chance you'll need to change your fuel filters too. we had to drain and clean the tanks on them. most additives back then were preventative, not for cleaning it.

I had issues with the sending unit in my A3.
Slime build up on the unit.
Used Biorbor JF for diesels and it seems to have helped.

There is free fuel filters in Pay it Forward which will probably resolve your problem.
Sounds to me like she sitting and doing no work. The new "diesel fuel" is crap.
Put some real seafoam or my favorite homemade seafoam in the tank.
Just go to HD and get some naptha put it in the tank and drive it.
How many engine hours does she run in a month?

pbranch it sure sounds like your not the only one having this problem read the posts sounds like you should get some resolution to the problem!
Karl

pbranch said:

I have an M35A3. There is a brass check valve at the fuel tank which is giving me fits. If truck sits for any length of time, the brass check valve develops a green sticky coating which prevents the value from opening thereby starving the engine of fuel. I have to disconnect the fuel line and remove the check valve from the tank, soak it with various items until it frees itself up again, then reinstall it. After that it runs fine until it is parked for a few days/weeks, then the process has to be repeated. So - any thoughts on what causing the brass check valve to gum up with a green coating? Anyone run into this problem and what did you do to solve it?

Click to expand...

I have an A3 that I've had for almost 10 years now. I had the check valve plug up about once per year. I always carry wrenches to remove the check valve and clean it. The check valve would always be plugged up with what looked like tobacco from a cigarette and green slime, along with particles of rust. The tank is aluminum, but I found that the rust was coming from the vent spring in my fuel cap. I tried cleaning it, but it would almost immediately corrode again, dropping rust inside my tank. The inside of my tank looked very clean. Looks can be deceiving. I eventually drained the tank and pressure washed the inside. I also rinsed the tank out with isopropyl alcohol in a hand sprayer followed by a hair dryer to dry out the tank. I use Optilube XPD fuel additive in my A3. This product is a very good lubricant when using the low sulfur fuel. After I cleaned my tank a few years back I haven't had a single problem. I also replaced the fuel cap with a new one. I keep grease smeared over the spring in the cap to prevent rust. That spring should be stainless, but isn't. I should also note that I seldom have any issues starting the 3116 engine after filter changes or when I cleaned my tank. The best thing to do is open the drain petcock under the filter assembly. Turn the engine over via the starter for about 10 - 15 seconds and then let the starter cool for about 2 - 3 minutes. I repeat this until the engine starts, normally about 3 - 5 cycles. As soon as the engine starts, I jump out of the cab and close the petcock. Normally, the petcock is plugged up with dirt from the road. When I first open the petcock, I rod it out with a piece of welding rod. The 3116 engine in my A3 is the fastest starting diesel engine I've ever seen. All I need to do is flip the starter switch and it starts, not even turning over more than one revolution.

YEP.

Not algae, diesel evaporating and leaving behind goo. My A2 does it (plugs up filters) when I let it sit in summer unless I add a lot of oil to the tank or Optilube Summer blend.