As more methanol is added to fuel it is becoming a greater consideration to the rallyist, particularly when visiting countries that use it in higher percentages. We first came across it in South America and more recently in Japan and we will soon be seeing more in Europe and the UK. In the UK we currently have E5 (5% ethanol) E10 isn’t far around the corner, it’s hard to find information about fuel in other countries. When we went to South America in 2011 we anticipated more problems than we had and in Japan we encountered more than we expected so from now on I will prepare cars on the basis that ethanol will be encountered.
It’s Nasty Stuff:
Methanol will make your engine run hotter, it is also hygroscopic and when mixed with petrol and water produces sulphuric acid, how much acid is produced depends on the amount of water the methanol sucks in from the atmosphere, this makes fuel with methanol more than just a very good cleaning agent, it will attack any rust you may have in your tank, gaskets and seals as well as eroding the lead solder that your tank may have been assembled with, and don’t forget your carburettor float.
All the years of good old fashioned four star fuel and damp garageing will have left deposits and rust on the inside of your fuel tank, while you may flush out the lumps there will still be a residue which the ethanol will turn into crud which will try to find it’s way into your fuel pump and carburettor, then the ethanol will wreak more havoc with older components as it gives them a good internal cleaning, often causing leaks where none were before. Fuel pipe can also be an issue, its best to use pipe designed for methanol fuel (teflon lined). Another point is that it gives the fuel a lower boiling point.
Give it a thorough flush out, preferably remove it, take out the sender and have a good look inside, make sure it is clean and rust free. You may choose to fit a new one or you could fit and auxiliary plastic boat tank.
This video clip is from a Ford flathead V8 that ground to a halt whilst climbing a hill due to fuel vaporisation, it probably took a good five minutes to get the carb stripped down to where you see it in the clip, and I was surprised to see it still boiling. There are things that you can do to alleviate the problem.
You can fit an isolation block and a heat shield between the carburettor and the manifold this will help, and is probably a good start.
Having the fuel pump in the engine bay doesn’t help either so if it’s electric it’s best moved to a cooler location where it can be readily serviced or replaced, the same applies to the filter which should be between the tank and the filter. Also note what sort of pump you have, is it a pusher or a puller, if it’s designed to push then get it below the level of the bottom of the tank so that it is constantly primed by the head of fuel from the tank, you don’t want the pump vapour locked.
You can also fit a fuel return pipe, your carburettor may have a port for this just before the float valve, if not just put a tee piece in just before the carburettor inlet, now you have constantly recirculating fuel back to the tank so the fuel is as cold as it can be when it goes into the carburettor. This is also an opportunity to get rid of your fuel pressure regulator if you have one by putting a restrict or in the return pipe to create a little extra pressure, a little experimentation with the size will help and loosing the regulator gives you one less thing to go wrong. The return can be braised or soldered into the filler neck or fuel sender with a bend pointing down, both of these are easily removed for safe soldering or brazing. A swirl pot will do the same thing.
Use Cunifer, copper or steel pipe as much as possible to minimise the amount of rubber pipe you need, and where you need rubber pipe it needs to be teflon lined.
Modern cars run fuel injection and pressurised fuel tanks, this raises the boiling point of the fuel, by sealing the tank and fitting a one way valve you can pressurise the tank as well. A pressurised tank will also reduce the amount of moisture the ethanol can absorb from the air.
Pumps and filters:
Fit a quality pump and carry a spare, select one that produces the correct pressure and volume for your carburettor, it’s pointless to fit a huge pump and then have to regulate it’s pressure down, all that happens is that both the pump and the regulator have to work hard against each other and will fail sooner.
It’s also worth noting that with most electric fuel pumps two or more can be connected in series (when switched off fuel can still pass through them). This is great because it does away with the extra valves and taps you need for a parallel set up and you won’t have stale fuel lying in the dormant pump also they flush each other and if both are weak they can work in tandem to get you home.
Carry plenty of cheap in line disposable filters fit one soon after the tank and be sure it has the right bore for your pipe size. Next I like to have a proper plant type filter with a water trap.
Fuel additives can help your engine to run more smoothly, octane booster however is not a panacea as many pre war low compression engines much prefer lower octanes, I remember running a three litre Bentley in Mongolia on 80 octane, we were hesitant to try it, she ran so well, it was like giving the old girl an extra gear.
The same applies though there will already be a return installed and the system will run at a higher pressure than a carburettor car giving the fuel a higher boiling point. You will need to have a good look at all the rubber pipes thar connect the injection system. Also don’t forget the fuel pump, it’s probably never given you any bother and because it’s made by Bosch you think you have no reason to doubt it. WRONG! when it encounters ethanol it could all go horribly wrong, first it gears noisy then grinding and hot and then it may start to leak