My Mk9 is very difficult to start. Ok while the AED/hisser works, IF I donˋt touch the gas pedal. When that shuts off at 32dec C, it likes to stop. If I then push the pedal half way and let go beforev I press the button, it will start and run for a few secs. Car is stored in a heated garage.
So I need to enrich the mixture! The carbs have a larger screw on the front, right of side the carbs, and and a small screw on the near, left side of the carb. Which one do I turn clockwise and by how much? (I think the small one by a quarter turn), but thought I´d check.
Thanks,
Peder
In my experience, if the SU carburetors are adjusted correctly then the engine will not be able to run very well when it is at 32 degrees C. When I rebuild Otter switches for local restoration shops I set them up to shut off at 60 deg. C. When starting from cold, the starting carb stays on for another minute or so but when it shuts off the engine is warm enough to run perfectly.
Enriching your mixture on the SU’s will perhaps mask the problem and allow the engine to run when it is cooler but at the expense of running rich when it is at proper temperature.
You are so right Mike. I will look into this. I know that the AED is adjustable by means of the screw at the top, but this might be foe enrichment only, when your point is abour increasing the time, in degrees, when the AED shuts off.
I have now read the section about the AED in chapter 3 in the Service Manual. The solution seems to be ”keep the hisser going for longer by short circuiting the Otter switch, after it has decided to cut off the fat mixture”.
Or shall I turn the screw anti-clockwise by half a turn?
On several other cars, which start easily, I stop the hisser by turning the ignition off very briefly. When I immediately turn the key again, the engine continues to run , and I avoid a bore flush. A few more minutes of warming up, and I am fine to drive.
whichever tuning compromise you settle upon, would it not be best to add a manual overide switch,
I have not seen any (older Jag) out here without one fitted, unless concours
I made a manual over ride for the AED by using the cigar lighter button. I am not a smoker and pressing it in activates the hisser and once I am moving above 30 I turn it off unless I get to a traffic light in the first few minutes and I can reactivate it as necessary. This prevents cylinder washing with excess gasomene that is not needed.
Gerard
A manual switch to operate the hisser is a common addition. On my car, using the under-dash manual switch to turn on the hisser requires the engine be off. Once running, the engine vacuum can pull the hisser closed with enough force that powering the manual switch will not re-open the hisser path. For me activation and re-activation of hisser by manual switch requires engine be off so as to open the hisser path on switch activation. A benefit of manual switch is the electrical lines to the hisser can be completely unpowered in the engine bay except when hisser is activated by manual switch, thus reducing a chance of spark-induced fire along those wire lines.
Roger. The trick to engaging the hisser while the engine is running is to energise the hisser and then a couple of seconds later blip the throttle. This will redice manifold vacuum enough for the solenoid to pull up the blanking disc. Geoff.
Hi Geoff, thanks for the tip about how to re-activate the hisser without turning the engine off. I tried re-powering the hisser followed by a throttle blip while coasting in neutral and it brought the hisser open again. Cheers.
Glad it worked for you. I found out about it by accident when I converted my series 2 from strombergs to hd8’s many years ago. I had a bit of trouble figuring out mixture strength and being able to engage the starter carb while driving was a big help in sorting it out.
Ok, this sounds exactly what my Mk9 needs, when it will typically stall at a red light when it turns green and I push the pedal…(this is of course during the first 10min before it gets thoroghly warm).
So this calls for a manual hisser switch. Fine, but then what? I turn it off when the engine can cope on its own, and running in N?! I then drive away without the hisser, but engage it ahead of that red light?!
But where does the engagenent by pressing the gas pedal come into play???
Peder
Peder,
The solenoid in the hisser isn’t strong enough to open the disc valve while there is much engine vacuum. Blipping the throttle reduces the vacuum, allowing the solenoid to lift the valve disc at which point the hisser starts operating.
An override switch allows you to energise the solenoid, but the hisser doesn’t actually start working until the disc valve is open.
here is how almost everyone I know in Oz wires there Jags up.
completely bypass the thermoswitch, and run a wire in the cabin to a lighted “choke” switch
To start, turn the switch on, and drive away, when the car is warm enough, depending mainly upon ambient temp, but also load, turn the switch off, which you will remember to do because it has a light!
If for any reason the engine vacuum is too strong the allow the ASC disc to be pulled open, blip the throttle, and engine vacuum will be overcome by the energised solenoid. This is rare
The main reason I dislike the ASC/HD arrangement, is that it is a compromise tuning that tends to be over rich, so if, like me, you do mainly short trips, that is a problem.
I do really like my HS8 conversion with manual choke, overcomes the issue completely
(and the open fuel vent in the engine bay to!)
Interesting, as always, Mike.
As I have several Jaguars from the 50s and 60s, I can chip in saying that some engines are ok with me stopping the AED, by quickly turning off and on the ignition, whereby they continue to warm up, but with less petrol washing the oil film off the cylinders. Other cars, esp the Mk9, would benefit from your 60 deg Otter switch. Today I attached a wire from switch to ground, to let it run for a few more minutes. BUT this car needs a richer mixture as the stalling at red lights, efen when fully warm, is very annoying. If on 4th, which is OD with my GM T700 box with the adaptor plate from Johnˋs Jaguar in Houston, and low revs, the engine will spit and sputter when I press the pedal. Going back to 2nd or 3rd is the solution.
So this engine might want the 60 deg Otter switch, and a slightly richer mixture…
I could be wrong, but turning off the ignition might foul the plugs and carbon them up and cause spitting. Are you able to go to neutral and blip the throttle (like a race car driver!) while waiting for a green light. I hard wired like Tony and sometimes have to flip the chock back on for 10 seconds at a traffic light.
Gerard