Not Starting

[dave_kitson]

Cabrio with Rover V8 on carbs. Turns over and fires like it is going to start, but immediately cuts out again. Any suggestions gratefully received! The car has been used every few weeks over winter, with no indication of impending problem.
Thanks - Dave

[lizbillings]

Is it pumping fuel through?
Liz

[greyV8pete]

Fuel. Blocked idle jet. Fuel pump. Choke not operating correctly. Sparks. If it has a ballast resistor then suspect that circuit.

[dave_kitson]

The fuel pump is certainly running - usual clicking - and was only replaced last year. I'm a bit reluctant to pull off a fuel pipe without considering other options. If fuel not pumping through efficiently, I would expect it to start and run for a short while on what was in the carbs (4 of them!).
I am starting to think it must be electrical, as it cuts out suddenly and completely. Trying to start again, it fires and cuts again. Ballast resistor burnt out??? Thinking on my feet here - while sat down!
Dave

[danny_nelson]

What dizzy set up are you using Dave? electronic or points and condenser? Check spark and go from there.

[danny_nelson]

If ballast resistor burnt out engine would start if ign key held over in start position.in my experience

[greyV8pete]

Back to basics. (Assuming not electronic ignition.. ) Piece of electrical wire and 2 crocodile clips. Disconnect wire(s) to coil + terminal. Hotwire direct to coil from battery and see if it will run longer. Only for a minute or two mind, just to prove ballast resistor circuit duff. Any longer and 12v direct to 8v ballast coil will heat it up! Unclip battery croc clip to stop engine.

[dave_kitson]

Thanks for suggestions.
Running on Mallory twin points and condenser. Is there any danger to the starter motor by holding the key over after it fires? Also - could the ballast resistor be simply bypassed so that the coil has 12v feed even after starting - any short or longer term damage likely??

I'm not likely to get to look at it today, so it looks like tomorrows MoT will have to be cancelled! Great timing!
Dave

[danny_nelson]

Same as Peter above, do not hold the key over long, just enough to prove it runs and stops as soon as key is returned to ign on position.

[A_Hogg]

Ignition switch maybe. Had similar on one of the Cabrio's I owned. Sometimes catch and fire up , sometimes not

[dave_kitson]

Cancelled MoT, humph!
Holding ignition key over proved it would run longer - thanks for tip, Danny.
Ohmeter across terminals proved it was dud. Could even see the break in the wire. Easily removed and new one located on fleabay - just awaiting delivery.
These things seem pretty standard, and usually have a resistance of about 1.6 ohms. At 12v, that equates to a current of 7.5 amps - quite hefty I would say.
Thanks for suggestions - Dave