Cold starting

[Ken Nelson]

Greetings from Michigan. It is starting to get cold around here this time of year, and I am experiencing a problem with cold starting. When the weather is above 50 degrees F., or when the car is warm, it starts readily. Otherwise it doesn't seem to get enough fuel, even with the choke (?"strangler" in Queen's English?) fully pulled out and functional. Is there anything besides the choke that could be affecting this? The engine is fully tuned with new points, plugs, coil, & wires, and the carburetor has had a new seal and jet kit put in 2 years ago. It otherwise runs flawlessly. Thanks for any help.
Ken Nelson

[Phil Nottingham]

Hi and welcome

Actually its the Cold Start in Roverspeak and is not even a true strangler as in the HD SU carb the jet is lowered and this often seizes partially in its tube due to petrol gum or hardening of the diaphram. Was the diapragm replacedwith NEW item not old stock and does it flex sufficiently

These cars should start very easily in very cold weather even on the handle if its not mixture it could be worn bores or tight valve clearances Check the compressions. Are the carbon plug leads new?

Tell more about your you and your 3 Litre

[stantondavies]

Battery performance can be an issue in cold temperatures. The engine is harder to turn over as the oil is thicker, and the battery voltage drops with the temperature.
What specification of battery do you use, and is it in good condition?

[Ken Nelson]

Thanks Phil and Stanton; The battery is quite new and turns the engine over readily, so that does not seem to be the problem. The engine has been rebuilt with new rings and bearings and the valves were lapped in so that is not likely to be the problem either. The valve clearances were reset, altho I haven't rechecked them lately. The carbon plug leads (ignition wires on this side of the Atlantic) are all brand new. However, it is perhaps likely related to the HD SU carburetor jet being gummed up or diaphragm stiffening, as the engine does not get regular use so far. I bought this car several years ago for $100 as a rusted out car with a seized up engine, and have been slowly rebuilding it over 5-6 years. The body is finally all welded up with 4 good used fenders purchased from California and the car has been completely repainted. I just finished putting the stainless trim and bumpers back on (would love to find a better rear chrome bumper bar) and will be starting work on the interior soon. The engine was rebuilt by me 4-5 years ago, and has often sat for weeks or even a few months without starting it up, since I haven't been able to drive it yet on the road. Is there any particlular place I should look to get a diaphragm from to be sure it lasts long if this one is bad? This particular car is a left hand drive 1966 3 liter Coupe that was originally sold in West Germany per the Heritage Trust certificate. It is standard shift with overdrive, and the speedometer is in kph and not mph. I believe they said only 25 cars were built to this spec, but have no idea if that makes it particularly rare or unusual? I shall try to investigate the carb diaphragm soon. Any other advice? Thanks, Ken.

[Phil Nottingham]

Interesting car. Three Litre Coupes in your part of the world must be extremely rare - manual as welll!

How long does it take to start - two or turns of the motor should be enough - 10 max

Assuming the timing is OK and the distibutor is earthing properly it could be just stale petrol. I do not know what sort of petrol you have out there but our unleaded goes off in about 6 months and does cause gums and resins that are difficult to shift.

The ignition switch can wear/corrode causing high resistance and thus low coil voltage when starting - this is easily checked by hotwiring but I do not intend to tell you how on this forum


It may be just lack of use.

The diaphragms can be got from Burlens and they will take unleaded fuel.

If yours is newish it would be well worth dismantling the carb to ensure you are getting full "choke" ie max downward jet movement, The fast idle linkage and cam can seize partially preventing full movement. If the diapharagm is flexible, not leaking or perishing it should last many years.

I assume you can hear the pump ticking on switch on to give full float chamber?

[patrickswan]

Phil, changing the subject slightly here , but you may have the solution the a very long poor starting saga on my mk2 3 litre with your comment on the ignition switch. Basicly the car has been almost impossible to start for ages, but particularly when warmed up. Often when cranking it over on the key, if I let go and let the key spring back to the `run` position the engine then attemps to,and sometimes does, start purly on the momentum of the flywheel. I have changed everything bar the back seat to try and solve this and am now tearing my hair out!!!!!

[Phil Nottingham]

The ignition switch may not actually be faulty! It will behave like this if the connextions to it are incorrect!

I do know this as I replaced one once and got the same symptons. Its just a matter of swapping them round

I assume you have checked your coil?

Note that wiring/switches on these cars can be well over 40 years old now - house wiring is condemned after 20 years max!

[stantondavies]

I had a lot of trouble starting my 3 litre when hot a while back. Changing the connections round on the coil solved the problem instantly. No idea how they came to be reversed???

[Ken Nelson]

Thanks again Phil and all.
I will try dismantling the diaphragm on the SU to check this out, since the engine certainly acts as if it doesn't get enough fuel in the cold. It will fire readily if I spray ether into the carb in cold weather, so I assume the electrical circuits are all working.

I am sure you are correct about my particular car being quite rare for this part of the world. One of my other cars is a 1954 Riley RME 1 1/2 litre, which is also uncommon here. I've seen them scattered here and there occasionally, along with an occasional Rover P4, but have yet to come across another P5 at a car show. I'm looking forward to driving this one next season to a few car shows and changing some of that! ;D Ken

[Phil Nottingham]

I hav eheard that once a car gets a liking for ether its hooked for ever and I do agree it does sound like a mixture problem.

Its easy to test this - next time its cold lower the jet screw manually by two turns AND pull the cold start fully open it should start immediatly as long as the float chamber is full

[Ken Nelson]

Hi Phil;
I'm happy to report that you were correct about the diaphragm not being fully pulled down when the choke was on . I have some more fiddling to do to reset the throttle advance, but I think this will solve the starting problem. My prior exposure has been with the earlier non-diaphragm SU carbs which seemed a bit easier to figure out. Thanks again, Ken

[Phil Nottingham]

Good - I hope it starst on the button from now on

Many an engine has been replaced and large bills paid out for unnecessary parts when its the simplest and cheapest things that go wrong and these should always be elminated properly first

[Ken Nelson]

Thanks Phil; It starts fine in the cold now. But I find that I can't slow the idle less than 1200 rpm, even with the throttle linkage removed and the butterfly valve apparently closed fully! It's obvious that this is just in the adjustments (ie it runs great). Any further advice? Ken

[Phil Nottingham]

The base idle speed is set by a separate mixture screw its quite large. The fast idle is also set separately this is on the dogleg bracket just under the cam for the choke cable.

These engines will idle as low as 350rpm if properly set up but somewhat highr is better to give oil splash - say 550 rpm