Cold start efficiency deteriorating

Dave3066

Dave3066

Well-Known Member
Hi gents

Just lately I've noticed that my car doesn't seem to start as well on full choke as it used to. Previously, to start the car in the morning I would pull the choke out to full and crank the engine until it caught, with no throttle applied. After several cranks the engine would fire up first time every time and idle nicely at fast idle. After a few second of this I'd release the choke to the mid position and it would happily idle at 900-1000rpm and off I would go.

Now when I start the car using the same method it doesn't seem to catch as well as it used to and when it does the idle varies from about 1000 down to 600 for the first few seconds, sometimes even cutting out. Once the car gets going I can push the choke all the way back in and the car runs fine. I suspect it's something to do with the choke and I've checked the operation on both carbs. All seems to be well visually.

I've done a bit of reading on how the choke works on these carbs but most of the stuff I've read relates to HS6 carbs. Mine has HIF6 carbs which I gather has a different cold start mechanism from the HS6. Looking in the workshop manual hasn't given me any clues as to how to set up the choke, but I did read something in a previous post on here about some 'o' rings on the cold start mechanism that have a habit of perishing. That post was about an engine cutting out when warm and mine does not do that. This only happens on cold start. When warm it fires first time every time with no choke needed and after a single crank. I also read somewhere that simply lubricating the cable can cure many choke problems, but the cable operation seems to be ok.

Any thoughts on where to start (no pun intended :D )?

Dave
 
Hello Dave,

When were the carburettors last overhauled in terms of having a new seal kit fitted throughout? If more air can be drawn into either, then the air / fuel ratio will change weakening the mixture.
How are the gaskets which link the carburettors to the tower looking?

Even though the engine starts normally when hot, this is less of an issue compared to when cold as the air/fuel mixture is also battling against condensation during that initial phase which is not an issue once warm.

Ron.
 
Ron

I've no idea when the carbs were last overhauled. It's on my list of things to do though. I've only had the car a little over a year and I can't find any evidence in the receipts I have to suggest an overhaul has been done recently. The gaskets look ok but looks can be deceiving.

Guess I'll be doing that before the winter then. Another first as I've never stripped and rebuilt a carb, now I have 2 to do :)

Dave
 
Have you tried using less choke to start ? There's no hard and fast rules with these, in very warm weather you shouldn't need as much choke. Plus if you give it too much to start with you do have the danger of flooding the engine. I generally start cranking with no choke and pull it out until the engine starts, then adjust from there.

Just my technique though ! :LOL:
 
I generally start cranking with no choke and pull it out until the engine starts, then adjust from there.
Click to expand...
That way gives the oil a chance to circulate before the engine fires as well
 
Dave,

Assuming your ignition set up is standard, I'd just give it the once-over. Give the engine a really good service, including tuning, but also new filters all round & new or reset plugs & points.

I did this with mine when it was rough & it transformed it, curing many ills in the process!
 
Phil Robson said:
Dave,

Assuming your ignition set up is standard, I'd just give it the once-over. Give the engine a really good service, including tuning, but also new filters all round & new or reset plugs & points.

I did this with mine when it was rough & it transformed it, curing many ills in the process!
Click to expand...

Phil

I have a pertronix kit fitted. The air filters are only about 4k miles old. I have a set of plugs I've been meaning to fit for a while so I'll do that ans see if it improves things.

Richard

I'll have a go at your method of starting and see if that makes a difference too. The carb refurbished kits are on the way so I'll be stripping them down soon.

thanks guys

Dave
 
You must log in or register to reply here.
Back
Top