hot start problem

Hi all,

This has probably been covered a million times but hope someone can help.

A couple of questions………

Just finished rebuilding the top end on my 1.8 cabby carb and also installed a new weber conversion kit as the Pierburg had a few faults with it - 3 point unit and cut off etc - if anyone is interested in it for spares, let me know.

1. The car starts on the button from cold (obviously with the manual choke out a bit) and also after being switched off for a few minutes.
However if I leave the car for 15-20 mins the car struggles to start. It eventually starts and then runs fine. Any ideas?
Have come across some posts on here mentioning the fuel running back to the tank or evaporating etc?

2. Also tested my coolant temp sensor (black 2 pin, only a few weeks old) in a pan of water and heated it up to 90 degrees and the resistance was around 80-85 ohms.
I have read somewhere on here that at around 90 degrees the resistance should be around 125 ohms? Is this correct? Tested it as my last post on here was regarding my temp gauge maybe reading incorrectly. With a thermometer in the expansion tank the fan cuts in around 88 degrees so I know the fan switch circuit is operating correctly.

Thanks in advance,

Ricky

Could be vapour locking, have you still got your vapour separator plumbed in? A valve in the pump could be bad. Are you getting any vacuum in the tank?

Hi Steve,

Thanks for the reply. Yes, still have the vapour separator plumbed in. Was thinking of fitting a non return valve in the fuel line to the carb from the separator??
If that works, it would point towards the tank/pump?
I have noticed there is a non return valve fitted in the return line back to the tank. That would eliminate it draining back wouldnt t? Unless that has failed which would be unlikely. Will wip it off and test it to make sure.

I have not checked for vacuum in the tank. Probably a daft question but whats the best way to test this?  

Cheers

Ricky

Don't know if it changed between years but my tank has a breather underneath the car. Some were vented through the filler cap. If the tank can't vent it will be under vacuum which will cause fuel to be sucked back. After the car has run for a bit, check for a WHOOSHING sound when you take the cap off. Can't say I've ever noticed a non return valve on mine so not sure if it should be there.

Still running the mechanical pump on the block?

If so it might be worth checking it.

Have you had the car set up by a professional? Sometime the wrong jets may cause issues with hot starting due to flooding the engine or indeed by not giving enough fuel at idle.

The fuel does indeed evaporate from the bowls of the carbs, that's why it may take a while to start. Give it a couple of pumps of the throttle cable before trying to start. Each set up is different and you almost have to learn what it needs to start in different conditions. If you use an electric fuel pump it can help with this problem as it effectively 'primes' the carbs prior to starting. With the mechanical fuel pump it takes the engine turning over to get the fuel up to the carbs.

A non return valve can help if you want to stick with the mechanical fuel pump.

Ian

Hi Steve,

Thanks for the reply.

I am not sure on the breather so will have a look into that. Have fitted the non return valve in the fuel line to the carb and it has sorted the starting issue so must be tank end like you say.

Hi Ian,

Thanks for the reply.

Yes, still running the mechanical fuel pump. Since fitting the new weber carb I have not had it set up yet. Have adjusted it slightly just on sound and runs nice but will be the first job when everywhere is back open.

In regards to my question in my original post about the coolant temp sensor, where would you guys recommend getting one from? Got mine from the local motor factors but it isn't giving the correct resistance.

Cheers  

Aha, sorry mate. For some reason I read your post as twin carbs.

In that case you can pretty much ignore what I said!

Ian