plus 2 stops after approx 10 miles

[ian]

Car runs fine for about 10 miles then loses power and stops.
Runs for short time when cool then same thing happens.
I have checked points, changed condenser, plug leads, and coil.
The problem persists.
Any ideas would be gratefully received.

[PeterK]

Has this suddenly started ?
Any recent changes to the car preceding the fault ?

Anyway, my initial thoughts while waiting for a call are....
Possible fuel related issues
- fuel filters blocked
- tank vents blocked, and vacuum build up in fuel tank reduces flow to carbs (leaving the fuel filler cap open would prove / disprove this one)
- fuel pump worn and failing to keep up
- float heights wrong, needle valves sticking

Ignition related issues
- balast coil system fitted but with standard 12v coil - after engine warms up, switches to 9V and not sufficient to power 12v coil reliably

[ian]

Not had the car for long but it had not been used since rebuild in 1995.
Was fitted with an electrical fuel pump but I fitted a new mechanical one.
Checked carbs for poor fuel, dirt etc, but seemed OK.
Have drained fuel tank - no sign of muck!
Thanks for response.

[roblotus79]

Just pop your head under the rear wheel arches and make sure there are no corks in the gas tank vent tubes

[ian]

They are clear - but good thought - thanks.

[ericbushby]

Ian,
Mine did that! Turned out to be the rotor arm which failed short circuit from arm rivet to shaft when hot. It started immediately once cooled down. A burnt bubble inside was only visible with a lens.
Or, just because your pump is new doesn`t mean it is any good. If you have webers check the fuel level through the jet cover with a torch. Mine was intermittent and pumped if it was having a good day, although it was very old.
That took some finding.
With these two faults both on at once it seemed like the car liked going out but was reluctant to go back home.
Best of luck. Tell us how you get on.
Eric in Burnley.
1967 S3SE Type 45

[archigator]

I had the same problem and found it was fuel-related. I have a mechanical fuel pump and had recently fitted an additional in-line fuel filter between the tank and the pump, where there was none before. However, apparently the filter was too fine and would not allow the proper fuel flow. Any trips under about 5 miles, no problem... any farther than that it would die on the road and not restart. Got rid of the filter... it runs like a scalded cat. Do you have an additional in-line filter fitted?

Gary
'71 Sprint FHC
Miami, Florida

[jerryh]

Hi

As Eric mentioned check the rotor arm there have been lots of problems with the riveted type, get a quality red one from the Distributor Doctor they are not cheap but this will solve the problem, the amount of people I know running classic cars that get the same symptoms as you and it's nearly always the rotor arm.

[ian]

Thanks for your responses.
Car does have an in-line fuel filter fitted between tank and pump (before my time) so will remove that.
I purchased a new rotor arm from Sue Miller but will check it.
Will let you know how it goes.

[Andy8421]

Not that Lucas were a shining light (no pun intended) of quality, back when I was a young man I only changed a rotor arm or dizzy cap when I trod on it.
Recently I have had no end of trouble with both rotor arms (burn through at the rivet) and dizzy caps (becoming conductive when hot). The rotor arms lead to complete failure, the dizzy cap had me puzzled for weeks. Drive for a few miles, car would cut out, leave it to cool and it would run again. Ended up having to drive it until it failed, strip the ignition system down by the side of the road, and measure the resistance of all the components.
When I found the problem, I could replicate it by putting the dizzy cap in the oven at home. I tested a number of new caps using the 'AGA' technique, only NOS Lucas caps passed the test. ALL of the new caps I tried had the problem to a greater or lesser extent.
The tell tale sign was a oblong moulding sprue about 2mm x 4mm on the outside top of the cap directly above the centre brush. All the caps I tested that had this sprue became conductive at high temp.

[ian]

Thanks Andy- I will check the dist. cap and rotor arm.

[alan]

have you flushed and cleaned the petrol ine from the tank to the pump. This is in a low position and sediment can build up in it reducing flow rate

[ian]

Thanks Alan, I have plans to replace the pipe.

[oldchieft]

When I found the problem, I could replicate it by putting the dizzy cap in the oven at home. I tested a number of new caps using the 'AGA' technique, only NOS Lucas caps passed the test. ALL of the new caps I tried had the problem to a greater or lesser extent.
The tell tale sign was a oblong moulding sprue about 2mm x 4mm on the outside top of the cap directly above the centre brush. All the caps I tested that had this sprue became conductive at high temp.

This forum is in my experience unique in the level of engineering excellence and scientific method.

Another example of fine, detailed work, well done that man!

Jon the Chief