Carb Heat for Sierra.

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gwagensteve
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Re: Carb Heat for Sierra.

Post by gwagensteve »

I doubt there is much heat transfer from the head to the fuel via the fuel pump.

It's not the temperature of the fuel thats the problem, it's the temperature of the inlet air as it mixes with the fuel - this is freezing the water vapour in the air. The atomised fuel along with the pressure drop across the venturi (vacuum) is chilling the air.

I think the last carburettor car for sale in Australia was a mitsubishi triton or similar, probably late 1990's. No, fuel hasn't changed since the introduction of unleaded in 1986, unless you're using E10 as this will exacerbate the problem as the ethanol is hygroscopic.

Just to be clear, are you still picking up your inlet air from the back corner of the engine bay between the battery and the guard?

I didn't think there was cold weather petrol, only diesel, but I could be wrong - this is because diesel waxes at very low temperatures, not a problem with petrol.

I know you've done quite a lot of work to your carb, are you still running stock jet sizes? Are you still running a stock thermostat and is the engine getting up to temperature when the ambient is low? If the engine is running cold, the carby will be too.
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luigi
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Re: Carb Heat for Sierra.

Post by luigi »

Hi Fellas.
Hi Steve.
The airbox, air filter and intake are stock standard.
The air into the airbox comes from 2 places. From behind the battery and from the hot air pipe, which comes from the exhaust manifold.(extractors on my engine) I can control the amount of hot / cool air with a 3 position switch. Its a manually operated lever. Position one is for ambient temp above 15 C. In this position it takes all its air from behind the battery box. Position 2 is for middle range. Position 3 is for temps below zero. In this position it takes all its air from the hot air pipe. Its still the stock system, except I have fitted a larger diameter pipe and extractors. On cold mornings I use the below zero setting.

I have never changed the jet sizes. As far as I know they are stock. I suppose some new jets would be worth a try?

I have changed the thermostat (about five years ago). The engine ran cooler with the old thermostat. It runs a bit warmer with the new one.
I don't know if the thermostat is a stock Suzuki Sierra one or not. But because the temp gauge sits nicely on half I think its working fine? Also the cabin heater works very well too. I have never had any overheating problems with my Sierra.

As I mentioned before, I have tried removing the fan and using electric fans only and also tried partially blocking the air to the radiator. The problem still happened.

As far as mods to my carby. I have removed the auto choke and the idle up. I removed the auto choke because I thought it was the cause. But it made no difference. It starts ok without it, so I left it off.

I will see how the new alterations work tomorrow morning.

Regards. Wayne.
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christover1
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Re: Carb Heat for Sierra.

Post by christover1 »

My 1.0 L did this. 2 things I did which solved my issue, was to turn off snorkel at the air filter, and fit the spacer in the carb that many lose or forget. I'm with Steve, probably not getting enough hot water to carby, for a number of possible reasons. I did see one carb heating badly due to excessive use of gasket goo :oops:

Until repairing mine, I found stopping a minute fixed it, as engine heat could migrate to carby, then off I went.
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luigi
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Re: Carb Heat for Sierra.

Post by luigi »

Hi Fellas.
Yes, attaching a hot water pipe to the side of the float bowl has had a very encouraging result. :D
I was able to drive as far as Spargo Creek before I had any freezing and even then it was acceptable (on a very cold morning)
Normally on such a cold morning I would have to stop at Bachus Marsh and again at Ballan and again at Daylesford.

I don't have a spacer between the carby and Manifold. I can remember there was a fiber spacer there originally. It looked very much like a heat isolating spacer. Which I thought was not what I wanted, so I left it off.
It looks like water heating to the base of the carby, or in my case, a lack of it is the problem.

I am very happy with the result.
Thanks everyone for theories, suggestions and help.
Regards. Wayne.
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