Amazon: really cold operation ?

[gjr0]

It was only about 4°F ( ~ -15°C ) this morning and the car was a pig to start. Granted I didn't go anywhere for almost a week but I had to resort to starting fluid get get so much as a pop out of it. Once it started and ran for a while, I think the carbs took a long time to quit icing up (no/very low idle with the choke in).

Any ideas to get it to start better ? Anybody figure out something to give the carbs a little warm air ?
Thanks
Greg

[Ron Kwas]

Greg;

"Any ideas to get it to start better " Presuming a good general state of tune...assure electrical connections are clean and tight, to minimize VDrops to Starter, Batt condition and State of Charge are acceptable, oil is winter weight, all which will allow decent cranking and Choke is well adjusted. See: https://www.sw-em.com/checkchoke.htm

"...something to give the carbs a little warm air ?" ...partially block Radiator and drive gently with partial (well adjusted!) Choke until Temp Needle is off the peg...

Reminder: The computer in the car, which senses operating conditions and adjusts for them, is YOU!

Cheers

[142 Guy]

Switching to NGK iridium or Denso iridium plugs can help with starting. The iridium fine wire center electrode is more resistant to fouling and will reliably generate a spark with lower system voltages that occur during cranking. NGK and Denso are the only brands that I am aware of that offer iridium plugs in the correct size and heat ranges.

Check to make sure that your electrical system is in good condition so that the coil is getting the highest possible voltage during starting. If you are prepared to spend some $, switch to the later permanent magnet starter motor. The permanent magnet starter motor spins the engine a little faster with the same supply voltage (which helps with starting) and it draws less current which means the internal voltage drop in the battery is less which means the voltage supplied to the coil is higher which also helps with starting.

What is the condition of your carbs? There is no one thing that can fix hard starting. It is a bunch of small problems which add up to a big problem which is effectively Ron's message.

With respect to air preheating systems, depending on your carb arrangement you might be able to retrofit the air filter box with air preheater arrangement from a 140. However, the air preheater will do nothing to help with starting. It is primarily there to improve cold weather operation and fuel economy.

[samaron]

Picked up my Amazon from a paint shop today. Been sitting outside overnight and all day in freezing temperatures. I only pulled the choke and turned the key. Had probably 1,5 revolutions on the starter when it fired. This has been my experience during the winter last year as well. No incense, Michael Jacksoning the accelerator pedal or any other trickery needed.

My car still has a 6 volt system and the carburetor has some vacuum leaks, but I have adjusted everything the best I can. All the electrical connections have been cleaned and the battery maintained. I keep the radiator blind pulled half way in the winter for quicker heating.

I do agree with Ron and 142 Guy. Make sure things are properly adjusted and that the electrical is in good shape.

[Derek UK]

Amazons don't mind cold weather but the choke settings must be correct. First 1/8" should increase the revs and the rest of the pull should pull the jets down equally. Full choke is OK but be prepared to push it back in again as soon as she starts. Don't pump the pedal. SU's don't have an accelerator pump and rely on the small gap between the piston and the bridge to provide increased suck to to bring more fuel out of the jet. After a getting her on the move push the choke back in to the 1/8" position ASAP. Might not work the first time.
If the car has been sitting, it's not uncommon for it to need up to 20 seconds of churning to get fuel to the carbs so don't get too worried unless your battery is rather tired.

[gjr0]

The car starts fine when the temperature is in the mid 20s (-4-5°C) for days at a time. Full choke pulls the jets down 5/16". Once it runs a bit the high idle is about 3000 rpm. Half choke drops the idle speed but then it falls on its face and stalls. Pulling the choke out just a little doesn't do anything until it has warmed up a bit. Then it works as advertised.

I'm tempted to try mixing half a tank of 87 (R+M/2) with the premium that I have been using to see if the more volatile fuel helps with starting. The drawback is that the motor has been bored out to 2 L and still has the 1.8 L head.

The calculated compression ratio is >11:1 (cc'd the combustion chambers). Burning a hole in a piston to get it to start does not seem like a good trade off. Or if the high octane fuel is even problem.

[gjr0]

12°F (~ -10°C) It started on the second try this morning. I had driven it yesterday.

[142 Guy]

Do an internet search on volatility versus octane rating and you can find about just any answer that you want. Some of those answers are legitimate and reflect the fact that refiners can change the octane rating by different means. So, maybe lower octane rated fuel is less volatile and maybe not. Minnesota probably qualifies as 'cold climate' and in some cold climate regions refiners create winter fuels which have a higher vapour pressure (more volatile) to improve starting. Sometimes they get this by blending more butane into the fuel which also boosts the octane rating, so depending on which refiner produced the fuel and what chemistry magic they carry out the high octane fuel might actually be more volatile. There are lots of octane enhancing products (ethanol, toluene, MMT .....) so impossible to be definitive.

If the premium you are using has high volatiles like butane added to boost octane and improve cold starting, one thing that might happen with the Amazon's vented fuel system is that the volatiles might be evaporating during warmer temperatures leaving you with a less volatile fuel blend in the tank. How old is the fuel that you are trying to start the car on?

Personally, I would not chase trying to alter the fuel volatility as a remedy to the cold start problem unless it was a case of replacing skanky 12 month old gas where all the volatiles had boiled off with new fresh gas.

I have a 1971 142 with B20E which has a 10.5:1 CR. Down to -20C it has been a reliable and quick starter. I have not tested below -20C because the 142 is stored during the winter months. The B20E has fuel injection which can make up for a lot of cold starting issues. All carbs need air flow through the carb to generate fuel flow and the SU is doubly cursed by liking a nice manifold vacuum. I have had a number of Honda four cylinder motorcycles with a similar carb design and really cold weather starting was definitely not their forte. If you want to help the SUs with starting an engine that spins over quickly to generate good airflow with good vacuum would be desirable. The path to that is:
- an electric system that is in good condition
- consider that switch to the more effective permanent magnet starter which will spin the engine faster
- run a full synthetic motor oil with a 5W-40 (or 50) viscosity rating. Full synthetics are better at maintaining the specified viscosity as the temperature drops. Conventional 10W- oils tend to develop a very molasses like consistency at around -20C.

If you are not doing it already, I would switch to a 5W- synthetic before I would ever mess with a home chemistry experiment of trying to blend fuels to increase their volatility.

[Derek UK]

"Pulling the choke out just a little doesn't do anything"

That means that the choke cables aren't set properly to just increase the revs before they start to pull the jets down. Explanations and diagrams in the manuals are often not very clear but if you follow them word for word it usually works out. It's the relationship of the adjuster screw to the small cam that is important. Using those screws you can adjust the revs to about 1200-1500 before the jets go down. That usually means that after a minute or two or a few hundred yards you can push the choke in from the enrichen part to the high idle part. The higher idle will usually keep it running with none of the usual hiccups. It's easy to forget that the choke is out that little bit until you come to a junction, or much further into your trip, but once the needle on the temp gauge starts moving it will usually mean you can push the choke fully home. With the choke fully home there should be a few thou between the adjuster screws and the small cams. Have fun.

[simonvolvo]

I have painted a line on the shank of the choke pull, to make it easier for the “computer” behind the steering wheel to tell at what point the jets are starting to be pulled down. (Requires proper set up of the adjuster screws-to-cams.)