Almost messed up this morning

Actually I did mess up a little bit - sure could have been worse.

Low on gas and in a hurry this morning, went to fill up, opened up the flap and started to open the gas cap when I noticed the whole gasket area was full of rainwater from the storm last night.
Didn’t completely remove the cap, but enough to be concerned. Fished around in the toolbox looking for some baling wire, luckily found some and poked it down the drain tube. Rainwater drained away and I got the muck out of bottom as best as I could for the time being.

When I removed the gas cap, there was about 2 or 3 inches of water sitting on top of the inner flap - thank god there was an inner metal seal or I’d be screwed. Got a rag and wicked the water out of the filler pipe, finishing off with some paper towels.
Satisfied I’d got most, if not almost all of the water out, I filled the tank. Thought about getting some methyl alcohol later but remembered having some alcohol in the door pocket (covid thing, right) so put about an ounce or so in for good measure… what crossed my mind though was that gas these days is laced with ethanol so maybe water in the fuel ain’t such a big deal? Don’t know. Belt and suspenders approach was my solution.
Car seems fine after the experience but must check after heavy weather …the drain doesn’t block THAT often, but it does block.
Note to self - remember to check before opening gas cap!! :-1:

Good reminder for us all, Larry. I always check.that drain when I wash the car, and carry a coil of plastic weed trimmer line in the toolbox in my trunk (boot). The line is long enough to extend past the end of the drain hose that exits beneath the car.

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Huh! That was a close one Larry but you managed to save the day. :+1:t2:

Lads, I always check too, but for some reason I didn’t and it only takes one time … :roll_eyes:

I’ve been there and done that myself Larry. I usually make a point of checking under the flap after heavy rain but the one time I didn’t I found it full of water at the petrol station as I went to fill up. It was right up to the top of the filler neck, I quickly screwed the cap back tight and used a piece of guitar gut string I keep in the boot to clear it. I don’t know how much water managed to seep in, I was heading for a 160 mile round trip and it was on my mind all day but luckily the car ran fine.

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In my neck of the woods (Southwest Missouri USA) ethanol-free premium (91 octane) fuel is available and that is what I use, so keeping water out of the tank is perhaps even more important.

I run basic cheapest regular (and have done for years with no ill effects) after spending great gobs of cash on premium during my first few years of ownership.
Seems to make no difference to the way she runs. Plenty of oomph and never a ping.

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even if using low octane in the car most any hiccups can be rectified by adjusting timing or getting spark plugs with a different heat range.

You can’t adjust the timing on an XJ40, sorry!

well if you cant adjust the timing you can change the plugs heat range. i had a caddy that pinged so bad i thought it was going to blow up but at the time i couldn’t always afford premium so i put in colder plugs and it fixed it right up.

What you mean, you can’t adjust timing?
Xj40 have adjustable spark distributor cap.

The cap only distributes and the spark timing is created elsewhere… maybe you can adjust the pickup but turning the cap does not change the timing Janno

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What is the effect of adding alcohol…not being chemist myself?


The idea is that water doesn’t dissolve in petrol but it is mixing with alcohol. So if you put alcohol in the tank it will take the water with it and out the tailpipes.

So, adding alcohol will negate the hygroscopic effect of ethanol in petrol? Sounds too easy to be true!


No, the ethanol mixes with and breaks up the surface tension of water in the gas (as it too is alcohol) …no need for additional alcohol if you run with ethanol gas. Water can’t bead up and mess with the fuel system.

So alcohol will not negate the hydroscopic effect of ethanol, it will add to it. :wink:

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If you add 5l of alcohol to each E10 fillup you’re driving with E20!
We want the hygroscopic effect in a way. As long as it’s not sitting forever E10 might help remove the condensation from the tanks, a good thing

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Ethanol attracts moisture and over time that moisture may settle out as water at the bottom of the tank - in effect causing a rust risk amongst other things. This is why the standard advice is to fill up with ethanol free if you intend to lay the car up over the winter. Abercanadian added about an ounce of alcohol after rain water got into his filler neck - because “it will take the water with it and out the tail pipes”.

So, if water settles out of the E10 on to the bottom of the tank over winter why won’t a fresh dose of alcohol do the same and “take the water with it and out the tail pipes”?

Water goes into the ethanol and not out.
I guess if you had that problem you describe adding more alcohol would eventually take up water. I have no idea what happens if the alcohol is saturated or what happens with way too much alcohol. I don’t think an ounce will do much either way.

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Is it true that the 10% ethanol fuel makes the car a little less critical of the octane of the fuel being used? I’ve been using mid grade 89 octane (US measurement system) and seem to have no issues with my 1990 4.0 liter XJ40.