Club Triumph

Engine very reluctant to start when warm. Starts no problem from cold, and runs very well otherwise. Any ideas?

Can you clarify what you mean by "reluctant"? Does it crank very slowly when hot? Churns over really fast but no sign of firing?

The former is probably a weak starter or a bad connection between it and the battery, or the engine earth strap. Heat makes things expand and a slightly-loose-but-not-a-problem connection could become a very poor contact on a hot engine.

The latter could be an over-rich mixture or a problem with fuel evaporation. You have a non-standard carb setup so excessive heat soak is plausible. Couple that with a worn fuel pump and you'll have lots of trouble with hot starts.

Hi Rob, 

Thanks for your input. The engine turns over at good speed, hi-torque starter and new battery see to that. I too suspected fuel evaporation and re-routed fuel line etc. At the mot, two weeks ago, the tester.commented that emissions were at the lean end of the range and could possibly be richened up a little, hence the confusion. It also has had new plugs and leads and uses electronic ignition.

Possibly the same problem as I had with the Holley I had fitted years ago. The fuel boils in the carb after switching off the engine. The fuel vapour is heavier than air and fills the inlet manifold driving out all the air.

This makes a super rich mixture that will never fire when hot.

Best cure I found was a readily accessible switch to the fuel pump. Switch the pump off about 15 seconds before switching off the engine so the level of the fuel in the float chambers is much lower and therefore there is less to boil away.

You can test this by pulling up the top on the inertia switch when the engine is hot and see if it helps.

My switch used to be on the dash where the choke knob used to be and was marked as a cooling fan to confuse potential thieves.

I have long since converted to efi so don't need the switch any more.

Neil

I found half throttle does the trick when warm.

Andy

Quoted from Andymoltu-

I found half throttle does the trick when warm.

 

Andy

This is a good tip.

First eliminate ignition problems as the cause.

Second, if you have a non-standard type fuel pump, then check the fuel pressure. Normal is 2.7 psi.  If it is much more than that it could be the cuase of hot starting problems.

Problem solved, fitted Filter King and hey presto, now starts easily hot or cold.

Thanks for advice.