annoying hot start issue

[86corolla]

I have a rather annoying hot start issue with no real pattern...
my car is an 1986 toyora corolla.with a 1.3 2e engine...
cold start up is fine it fires right up..
If i drive it then shut it off..Then go to restart with in say 2 mins then it will fire up..
but if I leave it for say 5-10 mins then it will crank and eventually fire...
iv tried holding my foot on the acclerator On the floor..iv tried half way up.quarter way up..pumping it a few times.
leaving the ignition on for a few secs before starting...
iv checked the tank breathers...
vac lines on the carb...
changed the plugs.leads.dizzy cap.air filter...now I'm at a stop.
can anyone help

[Kieran]

Had similar with my Scimitar.

Changed battery and it sorted it. Think the hot starts needed a few cranks and that was bringing the voltage down for the aftermarket elec ignition.

[86corolla]

Mar 8, 2015 19:52:59 GMT Kieran said:

Had similar with my Scimitar.

Changed battery and it sorted it. Think the hot starts needed a few cranks and that was bringing the voltage down for the aftermarket elec ignition.

That was my last suspicion cheers

[taurus]

Or it may be a vapour lock forming in the fuel line or pump. It will form a few minutes after stopping with a hot engine, then clear once it cools down.

[nomad]

^ had the same problem on my 60's Cortina (always started 1st hit from cold, when hot it either caught 1st time or just spun till battery was flat)
Never found the cause but a few folk thought fuel vapourisation.
For info, replacing normal fuel pump with 'leccy one made no difference.
Fitted 'leccy ignition - no difference.

The only thing I found that helped mine - remove airfilter before trying a hot start, then it normally fired ok.
Maybe flooding past a hot carb and pooling inside the manifold somewehere???

Hope you get it sorted, mine drove me bonkers for years!

[86corolla]

Mar 8, 2015 20:59:14 GMT nomad said:

^ had the same problem on my 60's Cortina (always started 1st hit from cold, when hot it either caught 1st time or just spun till battery was flat)
Never found the cause but a few folk thought fuel vapourisation.
For info, replacing normal fuel pump with 'leccy one made no difference.
Fitted 'leccy ignition - no difference.

The only thing I found that helped mine - remove airfilter before trying a hot start, then it normally fired ok.
Maybe flooding past a hot carb and pooling inside the manifold somewehere???

Hope you get it sorted, mine drove me bonkers for years!

Haha I love my car but the hot start is driving me mad...
would an exhaust fan in the engine bay help or is there a way of bringing the engine temps down maybe a bonnet riser kit like some fords had...
iv tried running duct work to force some air onto the carb but made little difference

[Kieran]

As said, could be vapour lock, but the carb should be full if it's running ok.

i only solved it after carrying another battery around and putting 12 volts straight onto the coil with jump leads.

Always fired straight up first cranky then, after spinnng over for ages.

[taurus]

How are you running it - standard or have you modified it? To me it sounds like a fuel vapour lock but generally there's three usual causes:

1. Vapour lock
2. Weak battery - can't cope with hot starting due to compression (a new battery ought to solve it - so you'd soon know if this was the cause. Check battery voltage at rest & cranking).
3. Over-rich mix, plug gaps wrong

In terms of vapour locking look at the fuel system being prone to heat, is a fuel line running near the exhaust, is there any reason why underbonnet temperatures are higher than they ought to be - etc.

You can try putting some heat wrap on the exhaust to prevent insulate it. The duct doesn't work once the car is stationary so it won't prevent the temp. rising. You could try rigging an override on the fan so it can run after the engine is switched off - that's one way to prevent hot spots forming.

It can be a pain to sort until you find the problem. I had a Cavalier with a mechanical pump that did it, a new pump did exactly the same, the third pump (different brand) was fine. Never found out why the first two did it though.

[86corolla]

Mar 8, 2015 22:17:53 GMT taurus said:

How are you running it - standard or have you modified it? To me it sounds like a fuel vapour lock but generally there's three usual causes:

1. Vapour lock
2. Weak battery - can't cope with hot starting due to compression (a new battery ought to solve it - so you'd soon know if this was the cause. Check battery voltage at rest & cranking).
3. Over-rich mix, plug gaps wrong

In terms of vapour locking look at the fuel system being prone to heat, is a fuel line running near the exhaust, is there any reason why underbonnet temperatures are higher than they ought to be - etc.

You can try putting some heat wrap on the exhaust to prevent insulate it. The duct doesn't work once the car is stationary so it won't prevent the temp. rising. You could try rigging an override on the fan so it can run after the engine is switched off - that's one way to prevent hot spots forming.

It can be a pain to sort until you find the problem. I had a Cavalier with a mechanical pump that did it, a new pump did exactly the same, the third pump (different brand) was fine. Never found out why the first two did it though.

Hi the engine is stock..
its done it since I bought it I think a battery will be next on the list.
and no reason y temps should be any hotter.
The exhsust is at the front of the car near the rad..
and all the fuel lines are yo the rear of the car along with the carb and intake..
iv noticed that my lights get brighter from idle if u rev it slightly

[taurus]

In which case it makes sense to begin with the battery. One thing I found with 80's cars is they sometimes like a bigger capacity battery than standard spec.

But you might want to also check the alternator output - check it's in the region of 14v.

Also - remember that an alternator won't recharge a flat battery to full capacity. Dynamos do but alternators don't. If a battery on an alternator system is low the alternator will replace the charge used to start the car, but it doesn't take it up to full capacity. Might be worth trying giving it a trickle charge and see if that improves it.

(You get folks on holiday and the battery goes flat at the airport. They get a jump start, drive 100 miles home and find the car won't start the next day. So they assume the battery has had it and replace it. In reality all they needed to do was to give it an overnight charge and the battery might have lasted them for years. They just assume the alternator would have fully charged the battery driving home - but they don't work like that.

[86corolla]

Mar 8, 2015 22:44:50 GMT taurus said:

In which case it makes sense to begin with the battery. One thing I found with 80's cars is they sometimes like a bigger capacity battery than standard spec.

But you might want to also check the alternator output - check it's in the region of 14v.

Also - remember that an alternator won't recharge a flat battery to full capacity. Dynamos do but alternators don't. If a battery on an alternator system is low the alternator will replace the charge used to start the car, but it doesn't take it up to full capacity. Might be worth trying giving it a trickle charge and see if that improves it.

(You get folks on holiday and the battery goes flat at the airport. They get a jump start, drive 100 miles home and find the car won't start the next day. So they assume the battery has had it and replace it. In reality all they needed to do was to give it an overnight charge and the battery might have lasted them for years. They just assume the alternator would have fully charged the battery driving home - but they don't work like that.

Will check the outputs tommoz and report

[86corolla]

Mar 8, 2015 23:02:45 GMT 86corolla said:

Mar 8, 2015 22:44:50 GMT taurus said:

In which case it makes sense to begin with the battery. One thing I found with 80's cars is they sometimes like a bigger capacity battery than standard spec.

But you might want to also check the alternator output - check it's in the region of 14v.

Also - remember that an alternator won't recharge a flat battery to full capacity. Dynamos do but alternators don't. If a battery on an alternator system is low the alternator will replace the charge used to start the car, but it doesn't take it up to full capacity. Might be worth trying giving it a trickle charge and see if that improves it.

(You get folks on holiday and the battery goes flat at the airport. They get a jump start, drive 100 miles home and find the car won't start the next day. So they assume the battery has had it and replace it. In reality all they needed to do was to give it an overnight charge and the battery might have lasted them for years. They just assume the alternator would have fully charged the battery driving home - but they don't work like that.

Will check the outputs tommoz and report

At rest the battery is reading 12.58 volts
and with the engine running it reads 14.36 volts

[taurus]

Sounds healthy enough, it's not like there's a dud cell in there. I'd still give it an overnight charge though and see how it goes after that. Also - make sure it's at least the right Amp Hour battery fitted.

[86corolla]

Ok will do
any other ideas if it's not the battery.
carbon build up..
old fuel pipe..
old fuel lines
curse word in the tank..
seems to do it less on premium fuel :/

[nomad]

Should have mentioned I often swapped batteries on my problem car, alternator always seemed to charge fine and the problem wasn't just one of our batteries.

Mar 8, 2015 22:44:50 GMT taurus said:

Also - remember that an alternator won't recharge a flat battery to full capacity. Dynamos do but alternators don't.

Live and learn - I thought once the motor started an alternator would charge the battery to full capacity. Am always happy to get edumacated
Guess my emergency routine about bump-starting old bangers then taking them for a good long drive to charge the battery isn't the best idea after all. Doh!