Starting problem

[HarryW]

My E is reluctant to start; on turning over on the starter, it seems dead; then after a few attempts it appears to almost catch - bumbling for a second or two at a two or three hundred revs, then nothing. On a couple of occasions it has eventually coughed more and more and then fired up, run upto 3k revs for 15-20 seconds, then simply died with no misfire or splutter and is unresponsive when a restart is tried.
I've worked over ignition and fuel; there is spark at plugs and fuel is delivered to the carbs (but what then?)
The coil (Lucas Sports), points, condenser and plugs are all virtually new; I cleaned the petrol tank sump (it wasn't bad) and put a new filter in over the winter.
My next step is to rework everything again :( but before I do has anyone any ideas that might help. Thanks in advance

[Heuer]

Harry

1. I assume the fuel pump is working correctly and delivering sufficient pressure?

2. How old are the ignition leads and caps? A new set of Moroso or standard ones is worthwhile if they are more than 6 years old.

3. Have you checked the SU carb filters? There is one in each fuel inlet port.

4. Always worth swapping out those almost new parts with known good ones to eliminate anything faulty. Coils in particular can fail from new.

[christopher storey]

Have you made sure that the rich mixture device is working? The brass pushrods which actuate the jets often seize in the carb bodies , and then you have a real problem trying to start from cold ( assuming this is a 3 SU car)

[HarryW]

David, Christopher,
Thanks for such prompt replies;
1. The petrol pump (via a Filter King) is delivering a pint in 30 secs or so to the carbs.
2. The leads and cap are 2-3 years old and 'look' OK
3. I checked the front carb filter - clean as a whistle- and didn't check the other two; but I shall.
4. Failure of 'new' components has been in my mind (I discarded my old coil as it was giving problems), but what particularly puzzles me is why on 3 or 4 occasions it has run, but then cut out in identical circumstances each time after 15 - 20 seconds. I'd be slightly less puzzled if it never kicked off at all!
5. Is the 'rich mixture device' the choke? All visible parts of the carbs - I've had the dash pots off and reset the mixture screws ( they didn't need it) - look clean and feel free. -And yes, it's an SU carb
Would trying a 'Cold Start' spray possibly overcome any symptoms, or is that best left alone?

[christopher storey]

Harry : it's certainly worth giving it a squirt or two of a cold start spray, but if it will run for 10 or 15 seconds in any event, it is unlikely to make much difference. The obvious cause of the problem is fuel orientated of some sort, but the tests you have done already seem to militate against this . Have you checked float levels - it sounds at least possible that the mixture is rich enough to get an initial start but that the engine is then choking itself ( overrich) to death , which would also explain why it is reluctant then to start at all again. Also check the needle valves, which if defective can produce the same result through flooding . Just another possibility - the exhaust is not choked up is it? No one playing silly buggers and stuffing new potatoes up it? Yes, the choke operates by pushing those brass rods up, which are attached at the base of each carb to a bell crank arrangement which pulls the jets down. It is worth removing all the dashpots and pistons and checking that the jets are all working correctly - both going down to provide rich mixture, and equally importantly, coming up again when the choke is turned off . You should be able to see fuel in each jet just below the orifices on normal mixture , and perhaps just, and I mean just, welling over the orifice on full choke. Check also that the pistons are moving freely in the dashpots

Having said all that, never forget the old adage that 90% of problems with SU carburetters are in fact attributable to Lucas ignition! particularly check the points

[HarryW]

Just a quick follow up to the start up prob.
I trawled Jaglovers to try to identify whether anyone had had similar symptoms to mine; the nearest I could find indicated a possible problem with the coil lead connection to the distributor. I had another look and while it wasn't perfect it seemed reasonable; then the acorn end crumbled as I manipulated it, so...
I'd thought of going over to electronic ignition, but haven't been totally convinced about the 123 system, so I bought one of these at http://tinyurl.com/28r39eh - thanks for the tip off, David!
Set timing statically (10 degrees BTDC) before removing the (original) distributor and plonking in the new one, lining up no.6 plug as near as possible to where it should be; good spark from coil, good spark to plugs - good, I thought, to go.
Turned the engine over - nothing except a very isolated loud bang. Further research suggested I might be 180 degrees out with the new distributor; I switched no. 6 plug lead for no. 1 etc, fired up - went first touch!
Still to finalise timing dynamically, but tick over seems smoother than before. Result! :D