Cold Starting Fail..

[adam73bgt]

Well its getting colder and its getting ever harder to start my MGB..

It started happening a while ago, start the car on choke, any throttle input before the car was warm would result in the engine dying and stalling if the throttle was held down for any length of time.

Bought a new 6v battery as one of the ones on the car was pretty dead and the cold starting improved, but now it seems to be getting a bit worse again.

the car works fine once its up to temp.

Its the standard B series engine running SU HS4 carbs, except for K&N filters, a lucas gold ignition coil and an accuspark stealth electric ignition system.


I'm a novice when it comes to driving old cars in cold weather so if anyone could suggest what might be up with the car (or my expectations of it running from cold) please help!

Things that I think arent helping are the fact that the throttle cable is poorly setup to the point where full throttle at the pedal gives about 1/2 throttle at the carb (tried to sort this before but it didnt go too well...), I thin the valve clearances may have opened up a bit since they were done over the summer or perhaps it could be a mixture issue?

also the engine ran on a bit when I turned it off yesterday..

so yeah any help is appreciated, even if its just telling me to be patient and let the car warm a bit before I go anywhere

adam

[jrevillug]

Ignition timing by the sound of it. I've experienced situations where the car will just about idle with a lot of choke, but the engine won't make any power unless you put the choke in - correcting the ignition timing cured the fault every time.

Also, Bs do like to ice the carbs, especially with K+N filters - soem ducting feeding warm air from round the ehxuast manifold to the filters might help a bit.

[adam73bgt]

Hmm it does misfire (i think) a bit if you drive it when cold so timing could be an issue, which is annoying as i had the timing done over the summer, though the garage who did it hadn't used their timing gun in some time...

Ah i hadn't considered carb icing, perhaps i could modify the exhaust manifold heatshield slightly, plus the car currently has no bonnet insulation as it pretty much fell off so that might not be helping either lol

[adam73bgt]

bit of a noob question to follow on from this... but can the timing be wrong for when the car is cold but fine for when its hot? cos the car will only be difficult to start and try to stall when its been sat overnight. Starting and driving it when warm, or even if its been only sat for a few hours is (usually) no problem at all..

any suggestions anyone?

[bortaf]

If it's anything like the MGB i rebuilt last year then give the throttle spindles a very VERY close examination, fitted new carbs and TBH it was transformed !
It now starts on the button with no choke and only needs the choke to be drivable IE no hesitation or spitting back, gained over 5 MPG as well on it's daily run, at that rate the carbs will pay for themselves

[adam73bgt]

hmm id like to have the carbs off for a proper inspection/clean up but what with the car being my daily its a bit tricky, i might try driving with the choke out a bit when its really cold too, up till now ive only really been using the choke when stationary...

haha 5 extra mpg would be a dream come true

[adam73bgt]

Slightly different issue now but i thought i might as well use the same thread as its relevant

The car decided not to start at all today, what exactly happened was:

turned the key to ignition, little red light comes on, then try to turn key to start and nothing happened. red light went out and nothing at all.

after a couple more tries and holding the key in the starter position for a little while, a faint noise could be heard, like something that had been stuck to something else being peeled away (random metaphor i know..)

after a short while the starter slowly started working and turned the engine over (just about)

engine would turn over on starter and coughed a little bit every now and then but wont start

does this sound like a battery issue with not having enough CCA? (it has two newish 6v batteries) or perhaps a starter issue?

i had been considering getting a 'high torque' starter and i may consider switching to one 12v battery if it helps (even though i just replaced one 6v )

any help is really appreciated as i need to use the car most days!

thanks, adam

[andyborris]

If it starts fine with a jump, then I'd look at the battery, if it makes no difference. starter motor or solenoid.

12v battery is a good conversion, if you Goggle it, you'll find lots of advice on sizes and fitting.

Do you know if the carbs were re-jetted when the KNs were fitted? They (the carbs) could be running a bit weak.

Look on the bright side, at least you can get all the parts very easily and at a reasonable cost!

[monkeep]

also, check the oil level in the dash pots in the SU's... do you know what oil is in there???
if it is too thick or if there is not enough of it you will have poor mixture control which will make the engine not respond to throttle input - like when you say it starts and then you press the throttle and it dies...

With regards to the choke, you should pull it full out to start and then gradually push it back in as the engine warms up. Its not a case of only using it when you're stationary to help the car idle...!

With regards to turning the key and nothing happening - check the batteries - but also check there are no shorts to earth in the wiring loom and make sure you have a good earth from your engine!

Otherwise some good advice on this thread so far! :-)

[Kieran]

2nd'd for checking battery - engine earths, and also the starter cables.

[trouble]

Nov 22, 2012 10:35:27 GMT adam73bgt said:

hmm id like to have the carbs off for a proper inspection/clean up but what with the car being my daily its a bit tricky, I might try driving with the choke out a bit when its really cold too, up till now ive only really been using the choke when stationary...

haha 5 extra mpg would be a dream come true

So the minute you pull away you just push the choke back in ?

You need to leave it out longer, and make adjustments when your driving. I use to push min in a little every time I stopped. Guessing the choke would be in operation for the first mile or so.

[adam73bgt]

I'm gonna borrow a jump starter off a mate to see if that'll get it started, id be annoyed if it was the batteries as they're pretty new!

i have to confess i didnt bother changing for richer needles when i fitted the k&n's as i was gonna wait until i fitted my freer breathing exhaust first to save changing needles again.. (still havent fitted it lol)

I've kept the dashpots topped up with SAE 20 oil (3 in 1 oil) which ive seen recommended in a few places on the net and in the owners handbook

Ah i probably didnt say that very clearly before, the car will idle without choke, but ive been using it while stationary to warm up, as moving off even with the choke out can still cause the car to bog down or stall :/

i shall be going round and checking earth straps to make sure they're all fine (or still there)

i had waited until the engine got up to about normal temp. then pushed the choke all the way in and the car would usually drive fine, i guess this is what you get when you plonk a young driver in a car with manual choke when they've been used to the 'turn key and off you go' method of modern cars

[adam73bgt]

got a 12 volt battery on order now, will boost my CCA from 290 to 400, should have done it in the first place really, ill be renewing some of the battery cables/ earth straps too. if its still sluggish to start then ill look at getting a better starter but i don't think (hope) it'll have to come to that

thanks for all the replies, ill let you know how i get on

[bortaf]

The trouble wit hthe twin 6V set up is if one battery is slightly dodgy it not only doesn't work as well it drags the other down so compounds the who saga one the one i rebuilt last year we had exactly the same problem, come time to start one of the battery has gone so we replaced the pair.

[optimusprime]

Nov 30, 2012 10:04:38 GMT adam73bgt said:

I shall be going round and checking earth straps to make sure they're all fine (or still there)

For a 'quick' test, use a jump lead from the engine block to the neg connection on battery, if it makes a difference you know you have an earth issue.
I used to have at least 3 earth straps on my 'old' cars.

[monkeep]

I don't think "3-in-1" is the same as SAE 20W...

And hence, when you open the throttle you're getting a mixture that goes very lean, combined with a slow airflow as the dashpot moves up too quickly - cue trouble pulling away when the car is cold!!

I would suggest something slightly thicker in the dash pots... but don't go wild, I ran out of straight 20W and used 10W30 motorcycle fork oil from Halfords - seemed to do the trick and worth a shot for a few quid... Was this a problem before you fitted the K&N's??

Sounds like a combination of at least part of all of the above suggestions so far! New battery will be a good start :-)

[penrhynrallycentre]

Right then lets start from the beginning

loosen the throttle cable on the carbs,make sure yoiu have 2 throttle return springs on the throttle bar,get a pair of pliers pull on throttle cable till you haer the pedal hit the top of it's travel....in other words rights at the top and NOT bottom where you would get full throttle,now make sure hte throttle spindel is SHUT on the carbs,if so tighten up the throttle cable.This is now set .
Make sur enow that the choke cable is fully in and that the choke is OFF on the car,if not adjust as necc....same as throttle !!!

Now look at the carbs and you will see a tickover screw screw it till you see the throttle spindle move whne you do unscrew it till it moves no more then screw back up by 3 FULL turns, this should give you a baisic setting,start car up on choke and let the engine get warm,you should notice that the idle of hte enginge is rather high,to adjust this you will need to adjust the tickover by means of the throttle tickover screw,set the tickover to around 800 to 1000 on your tacho and you wont go far wrong.


Dave

[adam73bgt]

after looking about the internet, it was suggested that that was the weight of 3 in 1 oil and many seem to recommend it, but i might try thicker oil and see how if it helps things at all

its hard to remember how it was without the k&n's as it was a while back now, though to be fair it was running fine on the k&n's when it was warmer so i think the cold air is having an effect (could be leaning the mixture as you say?) (might need to accept that i need to get richer needles also)


I had tried most of that procedure for setting up the cable, i found that it was very difficult to pull the cable any further through than where it already was. The pedal is a bit odd as you can pull it right up to the top, but then when you let go, it drops about an inch or so (maybe less) to where it wants to rest. I tried chocking the pedal up at its highest position and then pulling the cable through but it still wasnt having it..

the throttle spindle is shut when the pedal is at the 'top' of its travel, but going to full throttle doesnt seem to give full throttle at the carbs?

I shall have a closer look at the choke mechanism just to make sure thats not doing anything odd, and that its set up right

ill have a look at the idle screws too, i need to replace the nuts that currently hold them with a spring anyway

cheers for the replies guys

[ChasR]

If you need a hand I am willing to give you that (I do have a few items like a Timing light and an ignition tester at my disposale) if you are willing to throw a few beer tokens my way.

On both of my 'Bs engine oil worked fine for damper oil (20W50) although I have used ATF fluid in other cars with success (well, it worked a treat in the Dolomite Sprint).

Even with a weakish battery my 'Bs used to start on the button. Whilst the weaker needles will not help matters it should still start up fine unless the car was running super lean beforehand. I am tempted to go with an ignition issue.

[adam73bgt]

A hand would be much appreciated, as a beginner to this sort of thing, it really helps to watch what i actually need to do first hand, youtube and guides online/in books are only so good and I'm a student, my money is used for almost exclusively nothing but beer so that wont be an issue

hmm may have to try some 20w50 then, I'm fairly certain its the batteries as the car will start fine once the jumper pack is on there, ill know a bit more once i (finally) get the 12 volter in there, just gotta think where to relocate the earth strap