Miss-Fuelling (Putting in the wrong fuel).
What to do if you do it.
It was a Wednesday in the middle of August, a fine day and one I had planned to attend to the many family’s graves in Newport Pagnell. As I was to enter Milton Keynes, the town of a thousand round-a-bout with drivers who have no conception of the performance of 70 year old classic cars I fitted my ‘Slow Old Car’ warning sign to the rear bumper. The petrol tank gauge on my 1952 MG YB saloon was reading very low but there was enough for the sixteen mile trip. Later I pulled into the BP filling station in Tickford Street in Newport and proceeded to put in nearly 35 litres of ‘Ultimate’. Fuel. My odometer was reading 230 miles, which with an eight-gallon tank is almost 30 mpg. I always zero the odometer on filling up to keep a record of the car’s fuel consumption. There must haves only been half-a-gallon left in it before refuelling. With my new ‘BP’ points card I paid at the till and chatted to the lady about my old car she had observed at the pumps.
We left and drove into the cemetery across the road and attended to the family graves therein. We then drove to the High Street to a tea room for a cuppa and a bit of cake. But, as I drove past the Coop the engine began to seriously ‘pink’ (pre-ignition). After about fifty yards it just died on me. I though, ‘Oh hell, have I dropped a valve? Or burnt out a piston?” As we were opposite the *** public house I pushed the car into the car park adjacent, which only has a one-hour parking, no return for two hours. I was confused as once I turned the engine over with the starting handle it felt OK, compression on all cylinders. My wife by then had looked closely at the BP filling station’s receipt. It said “Die Ult” and not “ Un Ult” (unleaded).
DIESEL!! I had filled up with diesel. I’d never do such a stupid thing surely? Why did I not smell it when I operated the nozzle. I’m in the AA so phoned them, they told me it was not a break-down so they transferred me to their ‘Services Dept’. They would be with me in about 90 minutes but I would have to pay up front with my card, the £219 required. They would drain my car and give me two gallons of petrol. We retired to the tea shop and I went over the mornings actions. Why had I filled with the wrong fuel? I’ve had the car nearly 25 years, never done it before. When I arrived at the BP station, there was a big queue. I did not use my usual pump. When one became vacant I had pulled up to it, seen the word ‘ULTIMATE’ (which I usually use) and simply shoved the nozzle in the filler pipe and filled up. I had noted my tank was almost dry and that I needed about 30 litres. As my old MG has a big hole for a filler the bigger nozzle went in easy (modern leadfree cars have small opening that only the narrower leadfree petrol nozzle will fit into). I missed the fact I was holding a BLACK nozzle (diesel). There had been sufficient petrol in the pipe from the tank, and in the pump, to power the car over a mile into town as well as around the cemetery before it died.
The terrible noise the engine made was the last remains of the petrol/air mixture firing and that then exploding the diesel. Petrol engines use a spark to ‘burn’ the mixture, which does ‘burn’ and not ‘explode’. Your car’s ignition has a spark advancing system to cope with the piston’s speed as you go faster. The petrol/air mixture when it burns has a ‘flame-front’ that travels very fast but is not instantaneous. In a diesel engine it is the very high compression of the air in the cylinder (20:1+), reaching very high temperatures, that causes the diesel when it is injected at about TDC (top-dead-centre, the highest point the piston goes to before descending again) , to literally explode. For this reason diesel engines are very much more strongly built than your old MG’s engine (and why they cost a lot more). ‘Dieselling’ in a petrol, engine can wreck it by holing the pistons (but petrol in a diesel will certainly damage it as the petrol will explode far too early BTDC; Before Top-Dead-Centre, smashing into the piston before it reaches the top). Because the burning petrol in my engine had diesel in it, the ‘flame-front’ was an instantaneous explosion; that is the ‘knocking’ I heard where the force of that explosion was hitting the piston before it had reach TDC (doing this for a few minutes will do damage, so stop ASAP).
When the AA arrived, the operative had never dealt with an old car with a carburettor system. I explained I knew my car inside out and showed him under the bonnet. He then put up his safety signs (which were ignored by a least two people smoking cigarettes who came to watch and whom got the sharp side of SWMBO’s tongue) and ‘bonded’ his van to my car. Anyone who has worked on aircraft will instantly recognise the need for ‘bonding’. It’s a wire joining the two vehicles (or bowser to aircraft) to get them at the same electrical potential so there are no ‘static’ sparks when fuel is pumped. The car’s petrol tank was sucked empty but I had to remove the carburettor’s float-chamber top to enable him to suck out the diesel. I then switched on the ignition to pump the diesel out of the pipe from the tank to the carb for it to be sucked out of the float chamber. On a modern car with its fuel injection system and a pump to circulate the petrol this is not required (old cars simply pump to the carb; new cars pump fuel to the injection unit with excess fuel going back to the tank, so ‘purging’ the system). As the engine had burnt some diesel we removed the spark plugs and cleaned them. By now we had quite an audience who were impressed with the AA chaps care not to spill anything, using paper sheets under the car and engine, as well as under the carb’s float chamber.
He then put two gallons of petrol into the tank and asked me if I wanted the additive added, used to clean injector heads? This of course is not required in old coil ignition-carburated engines. I switched on the ignition and spun the engine over on the starter. It would not start. Then I thought of the jet-block in the carb that would still be full of diesel, albeit only a tiny amount. But it was enough to block the jet as diesel does not vaporise like petrol does. I pulled the choke out, this dislodged that diesel, and the engine burst into life with a big puff of white smoke from the exhaust. It had taken the AA 30 minutes to get us going again.
I drove back to the same BP garage and filled up with ‘Unleaded Ultimate’ this time. I saw that I had simply used the wrong nozzle from a diesel pump also called ‘Ultimate’. The same lady served me and gave me an odd look, wondering how I had used 30 litres in just three hours. I just winked at her.
If you see an old, bald-headed chap with a grey beard in a BP filling station repeating to himself verbally, Petrol,Petrol,Petrol; it’ll be me. My SU carburettor is now very clean and shiny, diesel is a good cleaning agent. I put this tale onto a couple of FB pages I use, no end of people came back and admitted they had done the same. It must be common for the AA to have specialist vehicles on the roads to deal with it. I asked the AA chap how many he did, he replied a regular four a day. It either gets ‘cleaned’ or sold to people who have dual-fuel engined vehicles. The best FB comment I saw was, “ There are two sorts of drivers “Those who have done It” and “Those who eventually will”. Not all will admit it.”
Neil Cairns.