Additional tips and checks

Realising that some of your vehicles may have been altered by previous owners, here are some original wiring diagrams and images that may help.

This advice stems from our experience with Jaguar V12 engines and relates primarily to that application. However, much of the advice is well worth applying to any vehicle installation.

Make sure original lead connectors and terminals are clean and protected from corrosion. HT leads and spark plugs should also be in good condition.

Where applicable, make sure the carburettor dashpots are filled to the correct level with the manufacturers recommended oil. Failure to do this can cause misfiring on light throttle due to the fuel mixture being too lean on acceleration.

Whether your engine has carburettors, or fuel injection, the fuel delivery system and the ignition system are interdependent. Many faults can be “Either/Or” scenarios, so ensure the fuelling system is also functioning correctly.

A known problem can be internal fracture of the amplifier connection leads just after entering the distributor. This is due to constant movement of the vacuum retard or advance unit. Hardening of the cable insulation from heat aggravates the situation.

The ferrite rods set into the outside edge of the distributor plastic timing wheel have been known to fall out. This is a very rare occurrence however. Be careful when removing the wheel, they can be difficult to lift off. Do not lever them on the outside edge or it may break. Secure any open-ended rod holes with a tiny dab of Araldite or similar. Do not use a large blob or it will set up a severe imbalance.

Another fairly common problem is the cracking of the mounting holes for the magnetic pickup inside the distributor. This can be fixed by using Araldite and a flat piece of similar plastic, about 3 or 4mm. thick. Remove the equivalent amount from the pickup’s mounting area on the carrier and glue the new material to it. When set, drill through to create holes that the mounting screws can bite into. If the new piece is carefully shaped, it can actually reinforce the “extension”.

A very common V12 problem is the centripetal advance weights in the base of the distributor and the advance mechanism being “stuck” with dried up grease. This will drastically affect the advance of the ignition timing and they need to be cleaned, freed, and lubricated with a high temperature lubricant. Again, be careful with the plastic timing wheel. Do not be alarmed by the fact that the two advance weight springs are unequal. This is how they should be. If you remove them, be very careful not to stretch them or reassemble them incorrectly.

The vacuum advance or retard module (carb. engines have retard, fuel injection has advance) is another weak point. The internal rubber diaphragm hardens quickly with age and heat then splits or cracks. This adversely affects engine performance, temperature, and fuel economy. New units can be bought, but I dismantled mine and repaired it.

The above may seem a bit daunting and you would be very unlucky to have them all. If you still have a problem after fitting the ReOpus unit, these are the items we would ask you to check thoroughly before you contact us for advice.

For more on ignition, carbs, and timing, visit Paul's Daimler Diary  Also, make good use of the Links To Friends page. You will find very extensive, useful, Jaguar V12 related information through these links.