1967 Jaguar 420 cold start problem
Discussion
Hi,car has done this since i bought it and i'd like to get to the bottom of it.Car has the XK 4.2 engine with two carbs.It has an otter switch setup which operates more fuel to go in at cold.Car will start,run up to where revs would be with choke on then it dies after about 6 or 7 seconds.It will do this two or three times until it eventually will continue to keep running.Car starts better from cold though blocking off the air intake going to the air filter housing.When warm the engine idles spot on and revs cleanly,anyone any ideas?Thanks.
Sounds like your car is fitted with an AER (automatic enrichment device) which works off the engine water temperature.
These are basically a small carburettor that allows extra fuel when the engine is cold. They are notoriously unreliable and yours probably needs dismantling, cleaning and setting up.
They are not very complicated and if you're at all handy you can do it yourself if you have the details. Try googling if you don't have a workshop manual.
These are basically a small carburettor that allows extra fuel when the engine is cold. They are notoriously unreliable and yours probably needs dismantling, cleaning and setting up.
They are not very complicated and if you're at all handy you can do it yourself if you have the details. Try googling if you don't have a workshop manual.
mph said:
Sounds like your car is fitted with an AER (automatic enrichment device) which works off the engine water temperature.
These are basically a small carburettor that allows extra fuel when the engine is cold. They are notoriously unreliable and yours probably needs dismantling, cleaning and setting up.
They are not very complicated and if you're at all handy you can do it yourself if you have the details. Try googling if you don't have a workshop manual.
Didn't know they were servicable!I'll do that tommorrow.It is fed from the cooling system by an otter switch in the cooling system,are they liable to break down?These are basically a small carburettor that allows extra fuel when the engine is cold. They are notoriously unreliable and yours probably needs dismantling, cleaning and setting up.
They are not very complicated and if you're at all handy you can do it yourself if you have the details. Try googling if you don't have a workshop manual.
The otter switch is a simple thermocouple switch which is fairly reliable. Not sure your symptoms would match that, unless the switch keeps cutting the AED/starter carb out. It sounds more like the starter carb that is the problem. Covering the air inlet would increase the vacuum and this could probably increase the fuel flow I guess. I can't remember which device is fitted to the 420, Jaguar switched between two devices at some point, but I can remember when.
There is a Haynes manual for SU carbs, but Amazon is wanting silly money for them second hand.
But I seem to remember the starter carb being very simple.
There is a Haynes manual for SU carbs, but Amazon is wanting silly money for them second hand.
But I seem to remember the starter carb being very simple.
http://www.ebay.co.uk/itm/JAGUAR-MK2-S-Type-420-MK... It's su hd8 carbs on mine (2 of) and here's a link to the enrichment solenoid thingy that sits between them.
rumpelstiltskin said:
Didn't know they were servicable!I'll do that tommorrow.It is fed from the cooling system by an otter switch in the cooling system,are they liable to break down?
They are very likely to break down. Worst case scenario is that your AED stays energised even when the engine warms up.
Back in the day many people would wire in a simple toggle switch under the dash so that the AED could be "switched off" manually.
When the engine is cold you should hear a distinct click under the bonnet as the solenoid is energised.
mph said:
They are very likely to break down.
Worst case scenario is that your AED stays energised even when the engine warms up.
Back in the day many people would wire in a simple toggle switch under the dash so that the AED could be "switched off" manually.
When the engine is cold you should hear a distinct click under the bonnet as the solenoid is energised.
Ive never really listened closely for a click,but when started from cold there is a hissing noise for a few minutes, then a pop noise like you do with your mouth then it feels like thats the choke off and when it behaves it will idle fine.This is when everything goes well!:-).I've taken wires off this solenoid with the ignition on, then put them back on, there is a click when reconnected.Worst case scenario is that your AED stays energised even when the engine warms up.
Back in the day many people would wire in a simple toggle switch under the dash so that the AED could be "switched off" manually.
When the engine is cold you should hear a distinct click under the bonnet as the solenoid is energised.
Sounds like it's working but needs setting up.
It so long since I worked on one I can't remember which type is fitted to your car.
This link may help, if not there is plenty of info on the web.
http://www.claymore.co.za/sherekhan/tech.html
It so long since I worked on one I can't remember which type is fitted to your car.
This link may help, if not there is plenty of info on the web.
http://www.claymore.co.za/sherekhan/tech.html
mph said:
Sounds like it's working but needs setting up.
It so long since I worked on one I can't remember which type is fitted to your car.
This link may help, if not there is plenty of info on the web.
http://www.claymore.co.za/sherekhan/tech.html
The one on that site is far more complicated than the one thats on mine.I posted an ebay link earlier to the type that's on mine.I think my one just basically lifts to let fuel in when it gets current from the otter switch, and shuts off when the water temp from the otter switch tells it too?There's a small 8mm nut on top of my Aed/aer, might be for some kind of adjustment?It so long since I worked on one I can't remember which type is fitted to your car.
This link may help, if not there is plenty of info on the web.
http://www.claymore.co.za/sherekhan/tech.html
rumpelstiltskin said:
http://www.ebay.co.uk/itm/JAGUAR-MK2-S-Type-420-MK... It's su hd8 carbs on mine (2 of) and here's a link to the enrichment solenoid thingy that sits between them.
That is just the solenoid that sits on top of the carb.it goes with one of these.
The bit on the right is a starter carb its sitting next to an HD8.
rumpelstiltskin said:
Here's a pic of my one.Looks the same,hard to tell as pics are at different angles.Top of my one seems to get wet when trying to start?You can see its damp in pic,side of solenoid damp as well.
MPH is talking about the wrong thing here. The AED unit was only fitted to the XJ6 from late Series 1 on.Edited by rumpelstiltskin on Wednesday 6th November 10:26
To check your auto choke unit is drawing fuel you have to short the terminal from to the Otter switch to earth. That will bring on the solenoid with a loud click. If it doesn't you have a simple electrical problem. If the switch does not activate the solenoid when cold it is faulty. If it does and the engine does not pull extra fuel and air through the 2 holes in the choke body it is likely that the rubber hoses under the inlet manifold that take the enriched mixture to the the engine are blocked. They go squidgy and close up over time. Renew these and then adjust the choke to the optimum setting by running the engine at idle, activating the solenoid and turning the small brass nut in the centre of the 2 holes in the unit until you get a perfect fast idle. You do this with a warm engine surprisingly; anti-clockwise will make the mixture richer; clockwise leaner.
J
Had a bit of a breakthrough,tested Otter switch and it was making the solenoid click,also listened for a click when i switched ignition on with everything wired up,it clicked!Then i decided just to try enriching the adjustment with the brass nut a little and it fired right up,ran with the choke(starter carb manual calls it) on for a few minutes,choke came off,idled fine,if a little low and lumpily!But im planning to rebuild carbs soon anyway just as a matter of course. One thing i did notice was the little glass bowl on the inner wing on the right hand side just has petrol in it,shouldn't there be a filter in it?I've ordered a fuel filter off Ebay but can't see in the manual where it goes,it just mentions a gauze filter that should be in the glass bowl,not the little paper element with a spring on top of it i've ordered below?
http://www.ebay.co.uk/itm/JAGUAR-E-TYPE-MK2-V8-420...
http://www.ebay.co.uk/itm/JAGUAR-E-TYPE-MK2-V8-420...
jith said:
MPH is talking about the wrong thing here. The AED unit was only fitted to the XJ6 from late Series 1 on.
To check your auto choke unit is drawing fuel you have to short the terminal from to the Otter switch to earth. That will bring on the solenoid with a loud click. If it doesn't you have a simple electrical problem. If the switch does not activate the solenoid when cold it is faulty. If it does and the engine does not pull extra fuel and air through the 2 holes in the choke body it is likely that the rubber hoses under the inlet manifold that take the enriched mixture to the the engine are blocked. They go squidgy and close up over time. Renew these and then adjust the choke to the optimum setting by running the engine at idle, activating the solenoid and turning the small brass nut in the centre of the 2 holes in the unit until you get a perfect fast idle. You do this with a warm engine surprisingly; anti-clockwise will make the mixture richer; clockwise leaner.
J
If you want to be pedantic it's not called an automatic choke either. To check your auto choke unit is drawing fuel you have to short the terminal from to the Otter switch to earth. That will bring on the solenoid with a loud click. If it doesn't you have a simple electrical problem. If the switch does not activate the solenoid when cold it is faulty. If it does and the engine does not pull extra fuel and air through the 2 holes in the choke body it is likely that the rubber hoses under the inlet manifold that take the enriched mixture to the the engine are blocked. They go squidgy and close up over time. Renew these and then adjust the choke to the optimum setting by running the engine at idle, activating the solenoid and turning the small brass nut in the centre of the 2 holes in the unit until you get a perfect fast idle. You do this with a warm engine surprisingly; anti-clockwise will make the mixture richer; clockwise leaner.
J
I did say the link may not be from his model as I wasn't sure when the later type was introduced. Now I know that it's from the XJ6.
In my original workshop manual it's called an enrichment device or auxiliary carburettor.
It's an enrichment device that works automatically. Call it what you will.
To the OP I can scan the relevant pages if you need more info.
My workshop manual is for a Mk2 Jaguar but I now assume it's the same type as fitted to your car, it's certainly the same as your photograph.
Edited by mph on Wednesday 6th November 15:03
mph said:
jith said:
MPH is talking about the wrong thing here. The AED unit was only fitted to the XJ6 from late Series 1 on.
To check your auto choke unit is drawing fuel you have to short the terminal from to the Otter switch to earth. That will bring on the solenoid with a loud click. If it doesn't you have a simple electrical problem. If the switch does not activate the solenoid when cold it is faulty. If it does and the engine does not pull extra fuel and air through the 2 holes in the choke body it is likely that the rubber hoses under the inlet manifold that take the enriched mixture to the the engine are blocked. They go squidgy and close up over time. Renew these and then adjust the choke to the optimum setting by running the engine at idle, activating the solenoid and turning the small brass nut in the centre of the 2 holes in the unit until you get a perfect fast idle. You do this with a warm engine surprisingly; anti-clockwise will make the mixture richer; clockwise leaner.
J
If you want to be pedantic it's not called an automatic choke either. To check your auto choke unit is drawing fuel you have to short the terminal from to the Otter switch to earth. That will bring on the solenoid with a loud click. If it doesn't you have a simple electrical problem. If the switch does not activate the solenoid when cold it is faulty. If it does and the engine does not pull extra fuel and air through the 2 holes in the choke body it is likely that the rubber hoses under the inlet manifold that take the enriched mixture to the the engine are blocked. They go squidgy and close up over time. Renew these and then adjust the choke to the optimum setting by running the engine at idle, activating the solenoid and turning the small brass nut in the centre of the 2 holes in the unit until you get a perfect fast idle. You do this with a warm engine surprisingly; anti-clockwise will make the mixture richer; clockwise leaner.
J
I did say the link may not be from his model as I wasn't sure when the later type was introduced. Now I know that it's from the XJ6.
In my original workshop manual it's called an enrichment device or auxiliary carburettor.
It's an enrichment device that works automatically. Call it what you will.
To the OP I can scan the relevant pages if you need more info.
My workshop manual is for a Mk2 Jaguar but I now assume it's the same type as fitted to your car, it's certainly the same as your photograph.
Edited by mph on Wednesday 6th November 15:03
The old choke device, and from memory Jaguar called it the Auxiliary Starting Carburettor was a great device and so easy to repair and set up with complete reliability.
J
rumpelstiltskin said:
Had a bit of a breakthrough,tested Otter switch and it was making the solenoid click,also listened for a click when i switched ignition on with everything wired up,it clicked!Then i decided just to try enriching the adjustment with the brass nut a little and it fired right up,ran with the choke(starter carb manual calls it) on for a few minutes,choke came off,idled fine,if a little low and lumpily!But im planning to rebuild carbs soon anyway just as a matter of course. One thing i did notice was the little glass bowl on the inner wing on the right hand side just has petrol in it,shouldn't there be a filter in it?I've ordered a fuel filter off Ebay but can't see in the manual where it goes,it just mentions a gauze filter that should be in the glass bowl,not the little paper element with a spring on top of it i've ordered below?
http://www.ebay.co.uk/itm/JAGUAR-E-TYPE-MK2-V8-420...
Glad you have made progress with your starter carb! Have set up, sorted out and reinstated quite a few of these on XKs and MkIIs etc, and one thing they most certainly are not, is unreliable, especially when measured against the mass infestation of so called 'automatic chokes' that followed on through the seventies. Some owners do indeed prefer to do without the otter switch and control from the cabin instead, no real need to at all though.. http://www.ebay.co.uk/itm/JAGUAR-E-TYPE-MK2-V8-420...
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