TECHNICAL TIPS - FUEL

PETROL PUMP LEAK:  If you notice a fine petrol spray appearing under the AC fuel pump to carburettor pipe connection, it could be that the solder joint at the olive had cracked, but on closer in-spection if it is coming from the small drain hole in the fuel pump, it could be that the diaphragm in the pump has a tiny hole in it, allowing fuel to pass through into the lower section of the pump.  In which case, the simple solution is to replace the diaphram so it';s worth checking the diaphram first.  Gary Munn DA7C)
PETROL PUMP PRIMING LEVER: The first warning I had of trouble was the engine cutting out while hurtling down a hill. Then the engine cut out completely while running at full chat. Removal of the float chamber showed it to be empty. While exhibiting at the rally with the bonnet open someone must have operated the manual priming lever on the AC T-type petrol pump. The lever had stuck. This meant each stroke of the pump delivered a reduced volume of petrol. The car ran perfectly for miles and it was only when driven hard that the restricted petrol supply manifested itself. A few strokes of the priming lever making sure it was left fully down and we were away again. Examination of the pump showed the priming lever’s arms to be binding on the external spring which is meant to return it. Two bright spots on the spring showed it must have been happening for some time. Slightly widening the legs of the lever allowed it to miss the spring, the lever moving up and down freely. Many of our cars will have the T-type pump and could be at risk. I suppose the problem is most likely to be at the start of the season if the car has been standing. I understand the alternative M-type pump doesn’t have a priming lever. Essex A7C with thanks.
 PETROL PUMP - FUEL BLOCKAGE: After repeated stops due to a fuel blockage on the way home from a run (cured temporarily by blowing down the filler tube on the tank!) The following day I removed the petrol pump and split it into two by removing the ring of small screws, expecting to find a split diaphragm which in fact was not the case. As the two halves came apart, a very small screw could be seen drifting quite remotely from the pump itself. In the upper part of the pump is what appears a small gauze held in place by three small screws, one of which was my offending screw. The ‘repair' was a simple reinsert of the screw and a check of the other two. The two halves of the pumps were reassembled, including use of the new diaphragm, and then reattached to the car making sure the foot of the pump, which is reinserted first into the hole of the crankcase, rests on the cam and is not hooked under it. This can be checked by slowly turning over the engine with the starting handle. If the pump is incorrectly fitted the en-gine will jam solid. Peter Trebilco DA7C
FUEL PIPE OLIVE: Whilst travelling some 1300 miles over some terrible Irish roads recently, the only minor incident we had with the Austin was a solder fracture where the fuel pipe olive joins the pump.  Not having solder and a blow lamp to hand, I cleaned the joint up, ensured it was dry and mixed up a little araldite. This was wiped over the olive and pipe covering the crack and left overnight.  We are still driving about like this some 1500 miles later!  To avoid cracking solder when undoing the pipe from the pump, always use two spanners, one to hold the union tight in the pump and one to loosen the pipe nut.  Sod’s Law says that if you use just one spanner to loosen the pipe, the union undoes instead of the nut, twisting the pipe and breaking the solder joint!
OVER-FILLED CHUMMY: I had just completed rebuilding a Chummy some years ago and went on a maiden voyage to club night. I filled the tank and set off.  Immediately after braking for a roundabout,  the engine compartment burst into flames.  Luckily, a passing motorist phoned the Fire Brigade and it was put out, but not before destroying the loom and taking the paint off the bonnet and scuttle.  Observations: Do not over-fill the tank, ensure you have a good fuel tight seal on the cap with a screw cap, not the bayonet type, similar to the oil filler which presents more of a challenge.  Also fit plastic HT plug tops and discarded the bare brass type which are asking to cause a fire if fuel is splashed on them, non original I know, but ......  Finally ALWAYS carry a good and functioning fire extinguisher with you.
The RUBY FLEXIBLE PETROL FILLER HOSE is an exact match to FORD part number 1416973.
NEEDLE VALVE: If you have a fuel supply problem check the fuel-feed needle valve assembly from the underside of the fuel chamber lid, it might have a speck of debris trapped in it giving an intermittent feed.

S.U. FLOAT VALVE FOR SCUTTLE-MOUNTED TANK:  If you have an A7 fitted with an SU carb and have a front mounted fuel tank that sits higher than the float chamber, it will probably leak fuel. The answer is to fit a replacement float valve kit that incorporates a viton rubber tip. These are available from Burlin Services (SU Carbs Ltd) and I can confirm that they do work. Geoff Kingsland DA7C
HIDDEN BRASS SCREW HEAD: Austin Seven owners, using the Zenith 26VA carburettor and suffering from poor, erratic engine idling can now improve the situation with very little effort. If you look at the underside of the 26VA you will notice a brass screw head in a raised rib about 30 mm back from the manifold flange. This has always been considered in the past as a blanking screw covering a passageway within the body of the carburettor. This screw plug is, however, an access cover to a jet underneath. Apparently this jet 'bleeds' a small amount of air into the throat of the carburettor when the butterfly flap is fully closed. If you hold up the carburettor and look into the throat from the manifold end you will see two small holes. The furthest one of these is the entrance to the jet which can easily become choked with dirt and leads to the rough idling. It can be reached by taking out the blanking plug and, with a good quality screwdriver which is able to reach far into the hole the jet, can be unscrewed for cleaning. Do use a good screwdriver as the jet is easily damaged You will be amazed the difference cleaning this jet will make. Another useful tip in association with this jet is to have your car ‘gas analysed’ on a Crypton tuner or similar. You will then be able to set the air bleed screw on top of the carburettor accurately. Note the setting by counting the number of turns out of the air screw that gives the accurate setting and always use this setting. Malcolm Watts Cornwall Austin Seven Club  
FUEL LINE BLOCKAGE 1: Geoff Hardman (CA7C) had a fuel-line blockage which he effected a temporary repair by blowing back down the line with a foot pump fitted with a beach ball inflator as a makeshift airline.  However, after a repeat blockage amore serious attempt was made.  This time, he dropped the bung and removed the first curly section of fuel pipe just in front of the tank. After considerable prodding and shovingan inch-long plug of what looked like varnish shot out of the tank uptake pipe. Then a piece of Bowden cable was threaded through the offending pipe. and spun using a hand brace (too much petrol around to use the cordless drill!) in an ANTICLOCKWISE direction. It unwinds inside the pipe, spreads out and buffs the sidewalls a treat. A final puff with the airline and we’re done.  Geoff Hardman CA7C
FUEL LINE BLOCKAGE 2: Keep a bycycle pump in the car to help blow-through the petrol pipe. Henry Nicholson-Cole DA7C
TO RE-CORK A PETROL TAP, soak the new cork in water for 24 hours which will encourage it to increase in volume and make a good seal once installed. With many thanks to “Bumbling” (A7OC)
TANK COATINGS PROBLEMS: Over the last two years I have had three incidents which left me stuck at the side of the road because of flaked tank coatings blocking the fuel pipe inlet at the petrol tank. Short of removing the tank it is a difficult problem to deal with. Our Box Saloon had a tank coating done by me around 30 years ago. It has caused me to be stuck twice due to on-going flaking of the coating. I have flushed it out twice and have found a small suitable filter to slip over the inlet to avoid pipe blockages. This is cheap and easy to fit and will suffice to keep you rolling. I recommend that when the fuel level gets to around a gallon the tank is drained into a bowl a couple of times a year just to avoid any major build up. The filter cannot close off the inlet to the pipe as the pipe is held in place by a metal stay. This in turn prevents the filter from closing off the inlet. The area of the surface exposed to the fuel filter area is greater than the inlet area of the fuel pipe. The protruding filter sits comfortably into the recess in the tank drain plug. The filter can be obtained from Austin 7 Components (https://www.a7c.co.uk/spares.php#nogo) part no BE24f in the catalogue index. Scroll down to “Fuel System” and it’s listed as “Zenith 22ZF carb filter” about £8.  George Mooney DA7C

NEW PETROL TAP CORKS are available from Brit-Bits in Barrack Road, Christchurch. Before fitting them do not try and reduce the diameter even though they may appear to be too fat. First boil them in a saucepan for 10 minutes to make them pliable then fit them on to the spindle, smear a little Vaseline on to the cork and ease it into the body of the tap, it may be a little stiff at first but will soon ease up when in contact with the petrol. Glyn.  Brit-Bits is open Wednesday to Saturday 9-1pm for callers, tel 01202 483675 and has moved to the rear of Smart Riders on 185a Barrack Road, Christchurch. The website www.britbits.co.uk gives an idea of the range of items stocked which can be sent by mail order.
THROTTLE ADJUSTMENT:  Did you know the accelerator linkage – the bit that pushes the throttle flap open – is adjustable?  It has a brass head on a threaded rod that can be screwed in and out (after removing the connecting ball joint).  See Bob’s photos.Put a heavy weight or wife’s foot hard on the accelerator pedal and check to see if the throttle flap is wide open.  If not, screw out the accelerator linkage until it is.  The result? – instant performance.  From an idea by Bob Kneale in the Cornwall A7C newsletter with many thanks.
INDUCTION AIR LEAK:  Air leaks into the induction system downstream of the carburettor jets will weaken the air-fuel mixture and can prevent a smooth slow tick over. The most common point of air ingress is through a worn car­burettor butterfly spindle. This can be tested by putting a blob of grease around the spindle at the actuating lever end and another blob over the other end of the spindle. If the tick over improves then the air leak was past the spindle. The cure is to fit a carburettor without a leak! Another cause for an air leak is a bowed carburet­tor flange where it joins the manifold. Repeated tightening over the years against a soft gasket gradually bends the flange. Finally, the state is reached when the centre of the flange does not touch the gasket although the "ears" of the flange through which the bolts go are tight down. This fault can be proven by putting a generous layer of gasket goo on both sides of the gasket. Again, if the air leak is now blocked the tick over will improve. The remedy is to carefully file flat the flange. David Fulton - Solent A7 Club
If you suspect you may have an induction leak around the carb or manifold, spray on some carb or brake cleaner from a can whilst the engine is running and, if the engine is sucking in air, there will be an immediate and noticeable increase in engine revs. Colin Chalk DA7C
 
MECHANICAL FUEL PUMP BLANKING PLATE: A neat blanking plate can very quickly be sawn, filed and drilled from an offcut of 1/8” steel and it is an ideal opportunity to add a bracket to carry the bottom-end of a second throttle return spring as shown in the photo.Kindly reproduced from the Herefordshire A7C with many thanks.

REAR PETROL TANK LEAKS: When you service the car, check the tank for leaks and rust by stroking the underside of the tank with the palm of your hand feeling for any slightly raised bulges.  It is fairly common for a leak due to a pin-prick hole to be contained by layers of old paint.  However, there is a simple solution - use a product called Petro Patch Putty available from Amazon and motor accessory shops such as Motobitz.  Empty the tank and let it dry out; scrape off the old paint bubble; rub back to bare metal and apply the putty; when dry, sand back to smooth.  David Whetton DA7C

ETHANOL PROBLEMS: Ethanol dissolves the lead and tin in the solder on fuel float (and possibly fuel lines and carburettor) and causes it to sink and flood. Carry a spare float. Ethanol Mate or John Deere Mate are fuel stabilisers. Some plastic floats are now available and hopefully A7 will be available soon. Supplier: Burlen Ltd. Salisbury. DA7C TECH FORUM