Sod’s Law with Respect to Ignition

I don’t know if it has happened to you, but I find that my T-Type invariably breaks down at the most inopportune moment, usually it is raining hard, or it is dark, or worse – both! Over the years I have developed a quick diagnostic technique for breakdowns, I carry a cheap yellow plastic spark plug tester in the driver’s side door pocket. Up with the bonnet, pull off a plug lead, insert the spark tester in circuit, turn the ignition on and pull the starter knob. If the plug tester flashes yellow, then it’s not the ignition, but most likely the good old SU fuel pump. However if the spark plug tester does not flash it indicates an ignition problem. More often than not I have found that the most likely culprit is the rotor arm, so the first thing to do is replace the rotor arm with a new spare, this usually fixes the problem, if not it is most likely the CB points or the condenser.

Now that I am in the latter throes of middle age (OK, I am an old age pensioner but reluctant to accept it!) my eyesight is not what it used to be, nor are my fingers as nimble! When changing points and/or condenser at the side of the road (in the wet/dark) it is very trying. It is all too easy to drop one of the little screws, washers or spacers, and never to be seen again you end up stranded. So a few years ago I came up with a plan to help me in these situations and purchased a new distributor base plate complete with new points and condenser (see photo 1).

I fitted the new base plate, complete with new points and condenser, to my TA and adjusted the CB points gap to the correct 12 thou setting and ran the car to check everything was OK. I then removed the new distributor base, and replaced it with the original one. The new one is then stored in my tool box along with a new rotor arm in a re- sealable plastic bag ready for instant use. If I break down now and the fault is in the ignition, I can change the complete points/condenser/rotor arm unit in minutes, with no set-up required. Just remove the LT wire (secured to the distributor with an old SU petrol pump screw cap), remove the cap and rotor arm, undo two screws securing the base and swap the distributor base for the new one.

The distributor base for the TA is different from that required for an XPAG, but all are readily available on eBay or from Moss etc.

Now once you are back home with the car safely in the garage, it’s time to find out what failed and replace the faulty component, and set up the distributor base for next time. I find that working on the distributor in situ is not easy, mainly because of eyesight and bending down problems. I find it is much easier to remove the distributor complete from the engine, and work on it on the workbench.

Now for tip number 2, to help you make it easy to remove and replace the distributor without losing the timing. This is much easier if your distributor is fitted with a micro-adjuster attachment.

This is how I do it……………

Firstly remove the distributor cap and leads, and move them out of the way. Make sure the car is not in gear and then turn the engine over with the starting handle until the brass tip of the rotor arm is pointing to one of the distributor cap holding clips (see photo 2), and then remove the starting handle. Raise the two cap securing straps vertically and secure the two with an elastic band as in photo 2.

Then remove the bolt that secures the micro- adjuster to the engine block (see photo 3).

Carefully pull the distributor out of the block, noting that the rotor will turn slightly anti-clockwise until the distributor is free. Make a mental note of how far the rotor moved, as you will need this info when replacing the distributor.

You can now take the distributor to your workbench, clean it, replace the required components and adjust the CB points gap easily (see photo 4).

When you are ready to replace the distributor in the car, refit the rotor arm, refit the rubber band to the two cap securing straps and turn the rotor arm until it is between the rubber band and with the brass tip pointing as in photograph 2. Then carefully turn the rotor slightly anti-clockwise a small amount (as noted earlier when you removed it) and push the distributor back into the block. Finally, check that the rotor arm is in the correct position (between the rubber band), and replace the bolt securing the micro–adjuster to the block. Remove the rubber band, replace the distributor cap and start the engine to make sure it runs OK.

If you follow the above procedure carefully you will not have to retime the ignition as long as you have not moved or removed the micro-adjuster from the distributor, and you have not turned the engine over whilst working on the distributor. I have removed my distributor many times using this method without any problems.

The Lucas part numbers for the TA distributor base are as follows:

• Distributor base (complete) 400164 or a bare base is 400001
• Contact breaker points are 400415 and the condenser is 400308

If you look around at autojumbles you can often buy and old base plate with worn components for around £5. This will provide you with the wire link and LT connector for your new base, or you can make one with black wire and a couple of spade connectors.

For an XPAG engine it is best to buy a kit of parts that includes a new base plate with a non-soldered new condenser. If you search on eBay there is a seller called automobileelectrics who trades as Classic Automobile Electrics Ltd of Scunthorpe, U.K. He sells a ’distributor base plate repair kit MG TC TD TF’ for £35 which looks good value to me.

Brian Rainbow