+2S spluttering engine issues

[types26/36]

I have not done this before so any tips before I attempt to take the carbs off?

Disconnect the battery terminal before doing anything fuel related and have a fire extinguisher handy before restarting!

[512BB]

'Am about to embark on changing the fuel filter(!)'

Where is this fuel filter that you write about? You are not talking about the fuel pump are you, that you have already pictured? If you are, it is highly unlikely to be the cause of the problem. Much more likely to be an electrical fault with either the dissy cap, rotor or condenser.

Good luck with it.

Leslie

[Graham B]

Hi leedsj,
I can't help feeling this problem is electrical.
I have had a similar problem where my S4 would start and run for a couple of miles and then gradually start misfiring, getting worse until it would not pull in top gear. Like your car, it would recover after standing for a time but repeat the misfire next time.
After many attempts and changing lots of bits, I resorted to disconnecting and insulating the wires from the loom and temporally wiring the coil directly from the battery via a spare toggle switch and fuse (mine does not have a ballast resistor, if you have a ballast resistor then wire to the resistor terminal).
It ran perfectly. I finally traced the problem to a faulty ignition switch, I replaced the switch and all was well. It appeared that the switch contacts heated under load and caused the volts drop, it was over 30years old!!
Note that when measuring voltages at the ballast resistor or coil the points must be closed. The resistor will only drop the voltage when current is flowing through the coil. (Don't leave the ignition on too long whilst measuring, the coil may get hot). Other voltages will be read if the engine is running. You should be able to measure about 12v at the connection to the coil or ballast resistor when the engine is running, anything significantly lower indicates a voltage drop between the 12v feed at the starter solenoid and the coil/ballast resistor terminal.

[alaric]

I think Graham is right. With my car I used a digital multi meter to check the resistance of the leads and plugs, and found two of them were much higher than they should be. I found placing the plugs on top of the engine I could see that the sparks were not consistently there, and were not all strong. It may be easier just to buy a new distributor cap with leads, and new set of plugs, and new set of points, then you know it's all new. You'll have to check the ignition timing if you mess with the points I'm afraid. As they are fiddly to set up, it may be an idea to fit an electronic replacement for the points that goes into the standard distributor. There are lots of posts about the replacements for points.

All the best.

Sean.