Volkswagon Polo 1993 Wont start if left a while when hot?

Question

The car starts ok when cold and if left for only a few minutes. If left for about 30 minutes it will not start until it is cold. I have changed the coil, leads and plugs but no luck. Anyone got any ideas. It is early fuel injection 1050 cc model.

Answer 1

A hot engine is hard to start if there's too much gas getting into the combustion chambers. That can happen if you have a leaking fuel injector. To see if that's the case, try holding the accelerator pedal all the way to the floor and crank the engine for up to 10 seconds. That tells your computer to default to the "clear flood" mode which stops any more fuel being injected and opens up the throttle plate for full air intake to lean out the mixture. If the hot engine starts easier, you can pursue an overly rich fuel mixture problem with your mechanic. A second possibility would be a heat sensitive electronics sensor or module like the ignition module etc. Finally, have your ECT engine coolant temperature sensor checked or changed. Remember "no start" means the engine cranks and the starter motor runs normally, but the engine won't fire and run. Make sure your air filter isn't clogged. Replace at 15 to 20K miles depending on driving conditions. Refer to your owner's manual for replacement intervals.

Answer 2

Sounds like a "heat soak" condition....what happens is when the engine is cold the starter will turn freely but when the engine gets hot, the heat transfers into the starter from the engine or the exhaust pipe and expands the armature causing it to seize up and not turn. Get a heat shield for the starter or wrap it in "header tape" which is a heat resistant tape that is used around headers...most parts stores or performance shops carry it. Good luck, Paul

Answer 3

As soon as you stop take the spark plugs out and perform a compression test, then do it again when cold, if you have low compression when hot, this is suggesting that the valves are being held slightly open, if it has followers and shims check the valve clearances to see if they have closed up, particularly when it is hot, if it's hyd tappets suggest you replace them or at least the ones in the set you suspect I:e ex or inlets. failing that squirt some oil down each s/plug hole and test compressions again, if improved suspect piston rings.