hot weather starting!!

[johngosnell]

In the last 4 years That I have had 1B1257BW she has always started on the Button, even now when starting in the garage from cold she starts first time, but after getting her out of the garage and being let in this hot sun she is having real problems firing up again. Once she does start she is fine with no issues, so I know some cars suffer from vapour lock but I am not sure. We in the UK are not used to 30deg (86f) temps. when starting I always allow the fuel pump to stop before starting.

Regards John


1B1257BW
19972 rover P6

[cass3958]

John it might be a conflict between the heat and your otter switch which runs the automatic choke.
The otter switch is a bi metal switch on top of the intake manifold, triangular in shape. ie three small nuts holding it in. The automatic choke or AED (automatic enrichment device) is powered when cold and allows the engine to start. When it reaches a certain temp the otter switch heats up and breaks the ground or earth stopping the AED from running. So the otter switch is closed to earth when cold and open not to earth when hot.
What you might be finding is that in the heat we have been having the AED is running first thing when the engine is cold and the otter switch is closed but the ambient air temp is such that the choke (AED) is not required and the engine is being over fueled. The otter switch which at this time is in cold water and is closed allowing the AED to work until the engine gets a little hotter and then it will break the circuit to earth.
If you disconnect the wire from the otter switch the AED will not work and the car should start first time again.
A lot of people including me have put a switch in line with the otter switch so it can be turned on and off from the dash alleviating this problem. The otter switch is on some older cars prone to staying closed as well meaning the AED does not switch off and the car will run very rich and burn lots of fuel.
Hope this makes sense.

[johngosnell]

Hi Rob thank for the detailed info, the car already has had a mod done so the choke is turned on or of by a switch. Not having an adjustable choke is an issue as the mixture cannot be adjusted. Ironically I did ask questions a while back about any mods so that an adjustable choke could be fitted.

Best wishes john

1B1257BW
1972 Rover P6

[NigelW]

My car had a bit of a problem in the heat yesterday, on the way to the Wroxall JEC show we stopped at a services on the M1 and when restarting it was running rough for a minute due to vapour lock. On the way home the heat in the car was terrible, it was painfull just touching the gear knob that felt red hot as it's an all metal item from an XJ6 with the O/D switch on the top. The engine ran fine at a constant 70mph with the water temp at or just below 70 deg and the oil temp at at around 95 deg for about 100 miles nonstop.

Can anyone suggest anything I could do to reduce the radiated heat from the engine/gearbox entering the cabin? It has all the standard sound deadening around the transmission tunnel etc. The gear stick and knob are a lost cause I think.

Out of interest there was only one other S Type (Register member) at the show out of about 1000 Jaguars.

[cass3958]

Most of the heat is possibly coming from the exhaust rather than the engine. Have you tried wrapping the manifold and down pipes in heat shield wrap. We used this stuff on my Lotus seven and our racing mini to cool the engine bay down with great results.

One in a thousand Jaguars. That sounds about right. I went to a Jaguar JEC event a couple of weeks ago and there were three S Types out of 500 Jaguars. Lots of E Types and Mk2s. Two a penny as they say.

[orlando]

Mine was the other S-type at Wroxall. Outnumbered by 420s! Phew, wot a scorcher of a day!

Firstly, on the subject of heat in the cabin, I took it fairly easy on the way home. My temperature gauge showed 80C. I have an AC Delco TF2 sleeved thermostat (68C) and 7lb radiator cap (tested at 5lb), but the heat from that engine is phenomenal. In traffic jams, my gauge will rise to 90C or just above, but it never seems to boil. I don't have an electric fan.

In 1992, my dad fitted a Double S stainless exhaust, which seemed fine when we put the car back on the road in 2015. But it was pretty boomy, had been knocked about a bit during the restoration and, after one 20 min traffic jam, the passenger footwell was so hot that my wife couldn't put her feet on the floor! A new exhaust from SC Parts last year helped immeasurably. The downpipes are further away from the floor. I also found that the heater air vents in the footwells were clogged up with leaves and not opening properly. Both now fixed.

Secondly, on hot weather starting. When my car was first on the road, I did have this problem. My AED is also on a switch, so that's never been a factor. I'm now at a stage where it starts on the button when cold and hot and after a few seconds churning when warm, which is good enough for me. Here are the things I did, in order of cost:

1. Depress the accelerator by an inch or two whilst pressing the starter. I think we probably all did this back in the day when starting carburettor-fitted cars, but fuel injection means you must never do it on a modern car, so we are probably out of the habit.

2. Use super-unleaded fuel. This seems to be less volatile and less prone to evaporation because it usually has less ethanol than ordinary unleaded. I have found Esso to work best, but ethanol percentage varies by region, so that may not be the same for others.*

3. Fit a 123 Distributor. Spot-on timing all the time. No points to worry about. Smooth tickover. Better economy. Better starting.

*A caveat to this is that, while standing under the car contemplating wheel alignment last week with Supertracker's expert, we were doused with about an egg cup of fuel which fell from the carbs (or more likely the AED) after about 30 mins of standing. So, super-unleaded is not the complete answer, I think.

I've also found in this 30C weather, mine doesn't really need the choke even from cold and, if I get her out of the garage and leave her for a few minutes, doesn't need it to restart (and will struggle to restart if I leave it on).

[NigelW]

Rob - the manifolds have been coated at Zircotec that reduces radiated heat by 20%. I might well try and wrap the downpipes as you suggest. I will also look into using a modern heat shield material fitted to shield the catalytic converters as fitted to my modern VW's

Orlando - really good to meet you at the show and get to look at your marvellous S Type. I'll post a link to a video of the show as soon as the replacement parts arrive to fix my brand new computer that failed today.

[orlando]

Thanks, Nigel. You too. I'll look forward to the video link.