Question about sediment/water in gas tank and poor performance when nearly empty (2 Viewers)

[Geezer Cruzzer]

I had previously asked about this problem without resolution, but now I have better possible handle on what is going on. So, here is the scenario... Miss Scarlet purrs like a kitten except when her tank gets down to about a couple of gallons. Then the engine will not run under load. It will start fine, no backfiring and idle perfectly but soon as I try to accelerate it shows classic symptoms of fuel starvation or water in the gas. Both times this has happened I've added HEAT and filled the tank. I let is sit overnight and everything is resolved.

After talking this over with a gear head friend, we're thinking that I've got sediment or water in the tank. I'm sure the tank has never been drained. So, what are your thoughts?

I looked under Miss Scarlet's dress and found what appears to be a large drain plug on the driver's side. It has a square 1/2" fitting. My Haines manual only shows a generic illustration of the gas tank. So, is this the drain plug? If it is, do you have any tips for removing it? Would also appreciate any tips on flushing out the tank after it is drained.

 

[coonassjohn]

It is the tank drain plug. You can use a 1/2 in. ratchet to remove it. Tie a rag around your arm unless you like gas on your armpit.
Drain it when it is at a low fill level. Don't smoke while doing this.

 

[coonassjohn]

You should have a filter between the tank and engine , if not you need to install one. I used an inspection mirror and flashlight to check the inside of my tank after I drained it. Try not to use ethanol gasoline, it makes water You can still buy non-ethanol gas at some stations. A little more expensive but worth it.

 

[40Man]

If you have sediment in the tank, removing the drain plug likely won't fix it. To do it right, you'll need to drop the tank and have it properly cleaned (many radiator shops have a heat tank that will work great, otherwise there are ways to DIY).

 

[Living in the Past]

If you let the 40 sit for a few days and loosen the drain plug if there is water in the tank it will be the first to come out. Big advantage is water that slowly drains past the plug is easy to dispose of verses contaminated fuel.
If it is water could get rid of most the water without draining the gas. Dependingg on the type of sediments would think those would plug the fuel filter.

 

[reddingcruiser]

You might run a tank of gas with some water-remover (STP, Valvoline, etc.) through the system before draining to improve your odds.
I'm sure everyone cleans their drain pans, but if you do start with a clean one you'll have a better idea of seeing how much crap comes out.
And yes, nothing 'burns' quite like gasoline in the armpit.

 

[Geezer Cruzzer]

Thanks all for your suggestions and insight. We're going on vacation for a couple of weeks. After I get back, I'll drain the tank and see what happens. I'll use a clean bucket to catch the contents. The last thing I want to do is drop the tank.

 

[reddingcruiser]

You can also look into the tank from the access panel in the rear bed. Get a flash light and look inside to see what is left after you drain it. You can also stick a clean shop vac in reverse on this port to ensure that all the water gets out.

Dropping the tank is fairly easy. Loosen the four rear body mounts, remove drive shaft and tank straps. It is about a two hour job.

Ummm. As a Certified Safety Professional (CSP), I HIGHLY recommend that you DO NOT stick a shop vac into a gas tank and turn the vac on, unless you are the proud owner of a highly expensive vacuum rated for hazardous/flammable atmospheres. Alternately, without bonding and grounding the tank you risk setting off flammable vapors with a static discharge.

Just my two cents worth.

 

[Geezer Cruzzer]

Ummm. As a Certified Safety Professional (CSP), I HIGHLY recommend that you DO NOT stick a shop vac into a gas tank and turn the vac on, unless you are the proud owner of a highly expensive vacuum rated for hazardous/flammable atmospheres. Alternately, without bonding and grounding the tank you risk setting off flammable vapors with a static discharge.

Just my two cents worth.

Makes sense to me. You could probably flick your Bic and have a good blow torch! Back in the early 70s I was an quality control inspector and had to crawl around in the wing tanks of military aircraft. Had to wear a grounding strap and did a lot of praying every time they sent me in. I was so lucky to be 5'5" and weigh 130 lbs. The old fat farts couldn't get through the access hatch.

 

[Splangy]

I don’t think that sediments and water care how much fuel is in the tank. If they’re present, they’re going to get sucked up no matter how much fuel is in the tank.

 

[WarDamnEagle]

You should have a filter between the tank and engine , if not you need to install one. I used an inspection mirror and flashlight to check the inside of my tank after I drained it. Try not to use ethanol gasoline, it makes water You can still buy non-ethanol gas at some stations. A little more expensive but worth it.

Ethanol doesn’t make water. Water is soluble in ethanol so if you use fuel with ethanol it will pick up the water into the fuel. On the positive side, if you have a clean tank and always use fuel with ethanol you will probably never have water accumulation in your tank. I’m not an ethanol fan but that’s the chemistry.

 

[coonassjohn]

Hate to start a peeing contest but your statement isn't quite factual. If you let the ethanol sit in the tank for awhile it will have water in it whether it makes it, absorbs it or invites it in for a ride, the water will be there.

 

[Splangy]

Hate to start a peeing contest but your statement isn't quite factual. If you let the ethanol sit in the tank for awhile it will have water in it whether it makes it, absorbs it or invites it in for a ride, the water will be there.

This is interesting. Does the ethanol absorb water from the atmosphere inside the tank? If so, does a tank full of ethanol allow more water vapor inside than a tank full of diesel or pure gasoline?

 

[Steamer]

I don’t think that sediments and water care how much fuel is in the tank. If they’re present, they’re going to get sucked up no matter how much fuel is in the tank.

Especially when driving and the fuel is sloshing around mixing up the sediments and water, making it available to the pickup tube.

 

[Steamer]

Vented fuel tanks breathe with temp changes which usually occur with alternating night to day. When the tank warms up, gas vapor is expelled. When the tank cools down, air with moisture gets sucked in. Then the moisture condenses and settles to the bottom. With Ethanol, a portion of the moisture gets absorbed, but it can only absorb so much. The rest settles to the bottom. The lower the fuel level in the tank, the more vapor there is, and the volume of the breaths are larger. Keeping tanks topped off will reduce the amount of moisture that gets in. That’s common practice in general aviation. Plane lands, gets parked and tanks are topped off very soon.

The homemade tank in my rig has the outlet on the very bottom and goes through a marine Raycor filter separator with a drain valve on it. I’m a weekend warrior and I drain out a fuel sample from the separator every trip. If I’ve topped off soon after a trip, I see no water. If I leave it at about ¼ full for a few weeks, I’ll see a small bubble of water in the bottom of the sample.

I believe all fuel tanks should have a drain valve on the bottom. The more convenient it is to drain a squirt, the more often it will get done. Of course location and clearances dictate whether a drain valve is feasible.

 

[Living in the Past]

Vented fuel tanks breathe with temp changes which usually occur with alternating night to day. When the tank warms up, gas vapor is expelled. When the tank cools down, air with moisture gets sucked in. Then the moisture condenses and settles to the bottom. With Ethanol, a portion of the moisture gets absorbed, but it can only absorb so much. The rest settles to the bottom. The lower the fuel level in the tank, the more vapor there is, and the volume of the breaths are larger. Keeping tanks topped off will reduce the amount of moisture that gets in. That’s common practice in general aviation. Plane lands, gets parked and tanks are topped off very soon.

The homemade tank in my rig has the outlet on the very bottom and goes through a marine Raycor filter separator with a drain valve on it. I’m a weekend warrior and I drain out a fuel sample from the separator every trip. If I’ve topped off soon after a trip, I see no water. If I leave it at about ¼ full for a few weeks, I’ll see a small bubble of water in the bottom of the sample.

I believe all fuel tanks should have a drain valve on the bottom. The more convenient it is to drain a squirt, the more often it will get done. Of course location and clearances dictate whether a drain valve is feasible.

From the early seventies all FJ40s had a non vented fuel tanks in the US markets. So a 82 if everything is working correctly will not be vented to the atmosphere. So shouldn't be pulling in moisture as the ambient temperature drops.

 

[Steamer]

From the early seventies all FJ40s had a non vented fuel tanks in the US markets. So a 82 if everything is working correctly will not be vented to the atmosphere. So shouldn't be pulling in moisture as the ambient temperature drops.

I never thought about it till just now, and don't think I'm being a wise a$$ because I don't know, but if a fuel tank is truly non vented, how does the gas get out? Wouldn't there be a vacuum in the tank as it drains? My little Honda generator will die in a few moments if I forget to open the vent. The pressure must get equalized somehow eh? I've seen large storage tanks collapse from the vacuum when drained and someone for got to open a vent. I'm just thinking here.

 

[Living in the Past]

If the gas doesn't turn to fumes I'm sure air can replace the used gas. But don't think the fumes are allowed to escape daily and be replaced by humid air. That would defeat the purpose of emissions. I doubt your Honda generator has emissions.

 

[Steamer]

If the gas doesn't turn to fumes I'm sure air can replace the used gas. But don't think the fumes are allowed to escape daily and be replaced by humid air. That would defeat the purpose of emissions. I doubt your Honda generator has emissions.

Yeh, I guess the vapor pressure goes through the charcoal canister and moist air going in is less but it must breathe some. I mean, a sheet metal tank can only handle so much pressure or vacuum. Sometimes I hear a little pressure equalization when I remove the gas cap on my non vented vehicles but it's not that much. I just think a system with a non vented gas cap has to be getting vented somehow. Maybe it's just restricted. I'm just thinking how much my plastic jerry cans change shape from late afternoon to the cooler am especially when they're partially full.

 

[WarDamnEagle]

Hate to start a peeing contest but your statement isn't quite factual. If you let the ethanol sit in the tank for awhile it will have water in it whether it makes it, absorbs it or invites it in for a ride, the water will be there.

Well it's a complicated subject. I don't think anything I said wasn't "factual" but let's go into a bit more detail.

Vented fuel tanks breathe with temp changes which usually occur with alternating night to day. When the tank warms up, gas vapor is expelled. When the tank cools down, air with moisture gets sucked in. Then the moisture condenses and settles to the bottom. With Ethanol, a portion of the moisture gets absorbed, but it can only absorb so much. The rest settles to the bottom. The lower the fuel level in the tank, the more vapor there is, and the volume of the breaths are larger. Keeping tanks topped off will reduce the amount of moisture that gets in. That’s common practice in general aviation. Plane lands, gets parked and tanks are topped off very soon.

Water is 100% soluble in ethanol (they do form an azeotrope at 95% ethanol and you need to take steps beyond distillation to purify ethanol beyond that percentage but that's irrelevant for this discussion - although it is why pure grain alcohol is only 95% pure, aka 190 proof). Ethanol is not 100% soluble in gasoline but is completely soluble at 10% solution (common E90 blend). The problem comes from mixing an ethanol blend with water. At 0.4% water contamination (3 tsp per gal) the ethanol/water mixture will separate from the gasoline and drop to the bottom.

Like Steamer said above, Ethanol can absorb a portion of moisture that infiltrates the tank but not too much. Here is a short article on the subject if you want some light reading: https://cropwatch.unl.edu/documents/Ethanol and Water Contamination 09052014.pdf

The major issue in my mind with ethanol (said I wasn't a fan) is that it has a shelf life of roughly 3 months vs 6 months for non-ethanol gasoline. Here is more of a layman's read on this subject (yes, Bob friggin Vila): How Long Does Gasoline Last? Solved! | Bob Vila

So when you let ethanol sit for more than three months or if it gets contaminated with more than 3 tsp of water (condensation or otherwise) then the ethanol/water mixture will drop out of the fuel (this will not be 100% but will be a very measurable quantity). So that "water" that coonassjohn observed is mostly ethanol but it will have whatever quantity of water that was in the mixture with it. Remember water is 100% soluble in ethanol and both are clear liquids so it will all look like water.

With non-ethanol gasoline, any water that gets into the system through condensation (and there won't be a measurable difference between ethanol or non-ethanol gasoline under the same conditions) will immediately drop to the bottom of the tank as water is almost 0% soluble in gasoline. The quantity will obviously be less typically in a non-ethanol gasoline tank as it won't have the ethanol volume with it; it will only be the water volume.

Bottom line for me, keep your tanks full, use whatever kind of fuel you want but use a fuel stabilizer if you are going to let the fuel sit for any length of time.

I have a 1985 4Runner and it routinely goes 2 years or longer with a full tank of ethanol gasoline without issue. I always make sure that the tank is full and I add a can of Seafoam to the topped off tank before I park it. I have also used Stabil without issue.

I will say that the first time I put ethanol fuel into this vehicle I had two plugged injectors within 20 miles of driving. (This was years ago.) The ethanol picked up the water in the tank and I had to have the tank drained, the fuel filter changed, and the injectors replaced (didn't have time or facilities to have them cleaned). Never had an issue since and I'm sure that most of the gasoline I have used has been an ethanol blend (Shell or BP mostly).