Technical Needs a lot of choke when cold

[btmaldon]

I know it needs choke when its cold but this 1988 45S needs it on full untill it warns up to at least quarter the way up the temp gage. Its a little embarrasing as it is reving the nuts off until I can put the choke back in.

There is no power without full choke until it has fully warmed up. Once it has reached temperature it still holds back a little (especially in third for some reason) but clears when I apply more gas. Its also fine when cruising at normal road speeds.

The car was off the road for 4 years and has only done about 50 miles since I restored it.

Its had new plugs and airfilter. Ive put Redex in the tank to try and clear it. Could it be a dirty carb, or do you recon it could be the ignition electrics?

Many thanks:worship:

 

[Chas Uno]

Is the ignition vacuum diaphragm working correctly?

 

[Chas Uno]

Oh yes, forgot to ask:

Does it tick over ok when warm? If not, is the idle speed set correctly?

Have you checked the ignition timing?

Has this only started since the weather got cold? If so, is your hot air flap in the air box working correctly and do you have the silver foil pipe connecting the airbox to the exhaust manifold?

Knowing the answers to these questions should help pinpoint the problem

 

[btmaldon]

Hi

Thanks for the responses.
I checked the timing Yesterday and its spot on.
It does have the silver pipe running from the manifold, However I haven't checked the flap in the airbox. Will have a look when I get a chance.

Im pretty sure the vacuun diaphram is working OK.

Did these distributors still have bob weights in the bottom of them? As I suppose these could be sticking a bit.

Cheers

 

[EssexUno]

I think they might as RandomSpeedFreak managed to break his dizzy when messing with the bob weights lol, search the forum and have a look.

Dan

 

[randomspeedfreak]

I think they might as RandomSpeedFreak managed to break his dizzy when messing with the bob weights lol, search the forum and have a look.

Dan

its true its true,
they do have bob weights, although mine is the 70, so i dont know about the specifics. all i can say is be very very careful, you cant find them for toffee (i guess finding them for a 45 would be a little easier, but still not something you want to be doing) - i had to bend mine back in the end.

It sounds like an advance problem to me. although its late and i cant think of a solution right now...

 

[btmaldon]

Thanks again guys.
The flap in the air box was loose and hanging open. After a bit of adjustment and a couple of washers its now closed. I just hope it opens when it needs to.

I found a split in the pipe from the back, lower part of the carb to the carb side of the air box. This fell apart when I started pulling at it, so have replaced it.

It should be OK now. Will find out tonight if I get a chance to use it.

 

[Chas Uno]

Make sure the flap is allowing warm air in from the manifold rather than only cold air, especially with winter approaching. The carburettor FIRE models are notorious for 'carb icing' often caused by a faulty hot air flap in the airbox, giving similar symptoms to that which you describe.

Make absolutely sure that the vacuum diaphragm is correctly working and that the vacuum pipe connecting it to to the carburettor base isn't split or leaking. The timing is drastically affected if the vacuum diaphragm isn't functioning. Talking of the timing, you did check it with the vacuum diapragm disconnected and the vacuum pipe plugged? It won't be set accurately otherwise

And yes, there are bob weights in the distributor but I doubt if there would be anything wrong with them as they're generally very reliable. In 70K of driving FIRE engined Unos I've never had problems with the bobweights - they only fail if you poke around with them (ahem RSF! )

 

[btmaldon]

I did check the timing with the vacuum pipe disconnected and plugged at 750 to 800 rpm with my trusty strobe gun. It took me back some years as it has been a long time since I was able to use any of my old tuning gear.

The air box doesn't have a flap on the manifold intake, only on the cold air intake.

All the other pipes I have either replaced or they are good. This includes a fuel pipe which had gone and could have ended with a rather hot feeling.

Hopefully I will get a chance to give it a run tonight to see if there is any improvement.

 

[Chas Uno]

I did check the timing with the vacuum pipe disconnected and plugged at 750 to 800 rpm with my trusty strobe gun. It took me back some years as it has been a long time since I was able to use any of my old tuning gear.

The air box doesn't have a flap on the manifold intake, only on the cold air intake.

All the other pipes I have either replaced or they are good. This includes a fuel pipe which had gone and could have ended with a rather hot feeling.

Hopefully I will get a chance to give it a run tonight to see if there is any improvement.

The thermostatic flap works on both intakes depending on whether it is fully open or fully closed. With the engine cold, the cold air inlet should be closed by the flap to allow only heated manifold air into the airbox. As the temperature rises the flap should move towards the hot air intake to allow a greater amount of cold air in, eventually closing the hot air intake off depending on the air temperature inside the air filter housing.

What did you set the timing to? From memory a 999cc FIRE should be about 2 - 4 degrees BTDC (I forget exactly which!)

 

[btmaldon]

I set it at two degrees BTDC.

Ive just been out for a run in it, and its much better when on choke now. I can push it back in earlier and no loss of power (if you can refer to 45bhp and power at the same time).

Still pulling back a bit in third and seems to be running a little rich. Maybe the thermostatic flap is not opening enough now.

I will check the timing again and the vacuum diapram as it was also pinking a bit when I put my foot down in the higher gears once it had warmed up.

 

[alexGS]

I guess you know that the timing must be set to 2-5 degrees with the vacuum advance disconnected - when you connect it, idle speed should increase quite a lot and you should have ~13 degrees advance. It's VERY common for the diaphragm to have a split in it. Also the thermostatic flap capsule usually fails -jam it in the hot air position for winter, it does make a difference. And the cooling system thermostat usually sticks open, so the engine takes much longer to warm up. All these factors combine to make the FIRE bog down really easily! They can run fairly well when running right, but there's always some need for the choke for it to pull smoothly when cold. It's not just for starting the engine (as it was on some cars).

-Alex