Here Goes!

[Tanky]

Hello all,

Firstly can I say how great it was to meet so many great and kind people at Duxford on Sunday. I was my first ever classic car show and what a great time Alli and I had. Bernie and Martin manning the shop certainly enjoyed my visit I think! Everyone we met was so lovely to us newbies and Duxford is certainly in the diary for next year.

I won't tell you all my woes, but on the way up to Duxford the Spit started misfiring quite badly. I pulled the leads as I thought that was the problem and with a nail file, my keys and my trusty teeth, I trimmed back all the ends of my leads and re-crimped them. This cured the problem for a while, but it returned. I spent Saturday morning in a taxi visiting all the motor factors in Cheltenham looking for new leads to no avail.

So arriving at the show on Sunday I duly bought new leads and rotor arm and fitted them. This seemed to cure the problem for a while but on the way back it started to misfire again, all the way home. It only starts to misfire when it gets up to temperature and it gets worse going up any kind of slope or hill, when it's cold it runs beautifully so I am now starting to think it may be fuel related, could this be true? When I pulled into the services and opened the bonnet, I could see fuel dripping from both overflows from the carbs.

So, if you would be so kind, could you start me off please, where to look first and what should I do? I hope this query does't send John's wrath my way again.....:)

(he is a terribly nice chap by the way). 

Thanks in advance......

Charlie

 

 

[Casper]

Clive, your cue I believe

C.

[Steve P]

My Herald does this going uphill,and i found the front carb overflowing,when i took the top off there was a release of pressure and i got a coating of petrol.Haven`t got to the bottom of this yet.Brand new pump with too much pressure?.

Steve

[Colin Lindsay]

Possibly just carbs running rich and requiring the mixture weakened; although one thing struck me about any kind of load on the engine ie going uphill - have you checked the timing?

Have you checked the plugs for rich running? Pull one and see if it's black and sooty.

[dougbgt6]

Dripping overflows means reservoirs are overflowing, because carb inlet valves aren't working. Could be stuck open or jammed with debris in the fuel. Is there a fuel filter? Normal place is just before the fuel pump, sometimes they're just before the carbs. If you haven't got one put it on the list. This may need a carb clean up, I'm not an SU expert, I have Strombergs, an SU Guru will be along shortly.

Doug

[KevinR]

Misfiring when hit could also be due to an overheating coil.

[Pete Lewis]

for repeated  flooding SU's   due to very fine ridged wear on the float needle valve platform   minor fettling wont solve this and needs a good magnifyer to spot the wear,  new float solves this .and the float valves dont last for ever

Floating slivers of hose ,, nasty little sods float about and randomly jam in the back of the float valve

 miss fires under load  dump the plugs and fit new , never with a R in the suffix, our   HT  doesnt work well on a resistive plug.

Pete

 

 

[yorkshire_spam]

I've been running bpr6es resistive plugs for well over 10k miles without issues. Your mileage may vary. 

[Pete Lewis]

Ive come across too many misfirer's with R in the plugs , if youre on megajolt with a higher HT fine but 

From experience with problems I hate them seems they put a cork in the pipe with our 22kv HT 

Let alone the insulation glaze being porous and accumulating  particle shorts to the plug gap where modern plugs are not suited to carbs and chokes fueling.

Its a first stop in any cough and hic up cars I end up with on the  drive and always solves the problem

Pete

 

[Tanky]

Good morning everyone. Thank you for your replies and expertise. So, to surmise....

1) Check Timing

2) Check plugs for soot. I (bought some from the shop whilst at Duxford)

3) Carb vales may be stuck/open/jammed. How will I tell, or is that a stupid question?!

4) Debris in the fuel filter. (I bought one from the shop whilst at Duxford)

5) Overheating coil. How can I tell if it's overheating? Should I just buy a new one?

Anything else?

Thanks lovely people..

Charlie

 

 

[johny]

Certainly for the cost of a coil its easiest just to buy a replacement and then you always have a spare if that isnt the problem. However there are two types used on our cars so make sure you get the right one.

With the carb flooding the float and valve assembly are in those pots next to carbs. Its a bit of a fiddly job as you have to disconnect the fuel supply and remove the top lid where inside youll find a float that when the chamber is full (it probably will be when you open it) push on a little inlet valve to stop more fuel coming in. If the float gets punctured or stuck it doesnt float anymore so cant operate the valve. You can inspect the floats and gently check their movement plus look in the bottom of the chamber for dirt. Then if all this looks ok a faulty valve is the remaining possibility and will have to be replaced along with the lid gasket that will probably have been damaged when you lifted it off.

Its unusual to have both carbs overflowing so I think either the car hasnt be used for quite a while and the floats/valves have got stuck or a lot of dirt has come through and affected both carbs.....

[Paul H]

Suggest getting carburettor cleaner aerosol . Ideal for carbs and cleaning off brake assemblies . Toolstation and Screwfix has this and it’s cheap . When I had carb issues a squirt in the air filters would assist starting especially in the winter 

If you post a pic of the plugs one of the gurus will give you the lowdown as to what tweaks might be required 

Paul

[Pete Lewis]

coils do get pretty hot ,some designs  are attached  to  the engine to act as a heat sink.

hot to hold, if it sticks to your hand it  too hot , do check the 1500 like many has a ballasted coil  this is a 6v coil the ign is via a dropper cable , when you crank the feed comes from the solenoid and gives the coil a 12v feed when you crank it up 

if this has been modified and by passed the dropper you end up with a 6v coil running on 12v   ye hah  really hot and this can blow points , condensers and rotors.

just to make it confusing some ballasted 6v coils are marked as 12v being the base electrics on the car 

a ballast coil is 1.5ohm on the ign.  terminals  and a 12v is 3 ohms 

there you go a bit more confusious

as for flooding just by a set of floats and new valves  *(dont get Grose valves   have a ball rather than a needle , used to be better but not now)

burlen fuel systems about the best in fueling  parts  they do a stay up float thats ethanol proofed

pete

 

[Tanky]

You guy's are brilliant! That's my Sunday sorted then......The car wasn't used properly for at least a year, but I have done in excess of 600 miles so far..

Charlie

[JohnD]

That's more like it, Tanky - investigation and observation!

And you have overflowing carburettor float chambers (almost as dangerous as the split hose!).     It all fits with your previous discovery of that, and repalceming it.     Small bet that you'll find pieces of rubber in the valves, so that the floats don't close them off as they fill and the pump keeps pumping until they over flow.   May not happen for a while, so appears to happen when hot, althougth the heat is irrelevant.      Overful chmabers might cause excess fuel in the mixture, which can choke the engine and cause a misfire and reduced power.

Carb cleaner won't touch rubber granules - you would need to remove the float chambers (oirkshop manual!) and blow through the valve orifices (airline, tyre pump, or tube in mouth!)   Look for fragments in the bottom of the chamber.   .

John

 

[Pete Lewis]

with supply disconnected when playing , crank or hand prime the pump and catch fuel in a jam jar . look for tiddlers , they hide

when refitting the hoses ....you can make some more ..... club shop new decent barricade hose is tougher and less of a sliver maker  dont get rubbish R9 from the fleabay

always check air filters are fitted so the vent holes line up with the carb face,  upside down gives major grief.

Pete

[Mark B]

My experience with misfires intermittent or not has been a faulty plug or plugs. First thing I would replace, despite if they look good or not. Didn't seem to be a problem years ago, but I've had cars that have been running fine then laid up and unused for several months, that have then developed a misfire on start up. Plugs looked like new, replaced and the car ran fine again. The only thing I can think of is damp and moisture gets inside the plugs and degrades them.

Mark

 

[Paul H]

Here’s a pic of slivers caught in the filter . Each sliver is enough to block the float valve and stop the petrol getting through . My issue was caused by fake R9 tubing from Fleabay , you need Gates Barricade from the Club though if buying quantity Moss is cheaper 

Paul

[dougbgt6]

4 minutes ago, Paul H said:

Each sliver is enough to block the float valve and stop the petrol getting through

Or, enough to wedge the valve open and cause flooding.

Doug

[Pete Lewis]

Mark  i guess your plug problem  is down to the makers not glazing the centre porcelain as reported in the spark plug post,

it makes sense as many of us are seeing unexplained early life plug failures due to modern made plugs not suiting carburetor fueling 

certainly ngk being the popular leader are now getting unreliable with the  many  .

 

Pete

[Dick Twitchen]

1 hour ago, Pete Lewis said:

certainly ngk being the popular leader are now getting unreliable with the  many

Several years ago Mark Fields (Jigsaw Racing) told me that NGK were being plagued by fakes.  At the time one thing to look for as starters was did it have 'Made in Japan' stamped on it.

Dick

[JohnD]

Spot on, Dick!   Here's NGK's own webpage on how to spot a fake:

http://www.ngk-sparkplugs.jp/english/techinfo/fake/index.html

John