Past her MOT... but..

[guymcc]

You will all be very pleased to hear that last Saturday 'Jemima' passed her MOT!!!

This has been after 18 months SORN'd and recently a lot of hours sorting out a back axle leak and a complete overhaul of the brakes that various cylinders seized and shoes worn etc etc.. oh and a dodgy fuel pump!

So to get it through the MOT was a huge sigh of relief to say the least, as i had i to drive it from Troon to Aberdeen on the Sunday after moving out of the house on the Sat!!!

but... after 5 mins of driving as she was getting up to temp everything was fine, even the extra temp gauge that the previous owner had had put in was working (seems to be temperamental!) until after that it seemed every time I applied more than half throttle it began to splutter and I would describe it as if the choke had been pulled. It was fine on only part throttle openings though. This proved a bit of a problem when climbing the large hill after Achterarder and also whilst navigating the numerous roundabouts in Dundee!

So any thoughts on the problem?
Mt own thoughts are (and I haven't had time to check it out!) are that it is something to do with the throttle rigging. I do know I have a problem with the choke cable, which I think is seized within itself and if operated it remains stuck out until one goes under the bonnet and physically resets it.

Any ideas or comments welcome!

Looking forward to some sunny days out in the North East!

[PAULJ]

Have you got a fuel filter? sounds like fuel starvation. Will it rev fully when not driving??

[bmcecosse]

Was the fuel consumption 'normal' ? Could be piston sticking in carb/fuel pump not delivering enough (what was done to fix it?)/points gap/ignition timing/choked air filter (try without)/vacuum advance not working....and so on. can't be too bad if it drove from Troon to Aberdeen! It certainly won't be the acc cable..........

[guymcc]

Still got this problem of when she is up to temp, she seems to cough a lot on more than half throttle. It sounds like maybe it is running too rich? Like it has the choke out? The ignition timing when last checked by a very helpful aa man was said to be very good.

I've ruled out the choke cable problem.

So yeh any pointers to a very amateur mechanic with the Haynes Manual!!

[bmcecosse]

What colour are the spark plugs? White = weak and black = rich. How did the AA man have nay idea what the timing should be ? Have you checked if the carb piston rises and falls freely ?

[kennatt]

check the oil in the dashpot

[robedney]

Pull the air filter off so you can see the piston in the carb -- as others have suggested. Stick your finger in (engine off) there and lift it (the piston). You should feel some resistance but still be able to lift it freely, and it should drop back down gently on its own. Yes, check the dashpot oil.

You can try warming the car up, then (bonnet open and you standing in front of carb) rev it up with the linkage at the carb. Can you reproduce the problem -- or does it only do it under load? If it starts to cough give it a shot of carb cleaner (the type that burns like petrol) and see if the coughing stops. If it does, it's lean and not getting enough fuel. If it gets worse, sounds like it may be too rich. And yes -- as suggested above -- have a good look at the spark plugs.

You're going to work your way through a proper diagnosis here -- like checking any fuel filters/screens, checking pressure/delivery at the pump, etc. There's also no guarantee that this is fuel related, so don't get stuck there

The smell of the exhaust might tell you something too.

[bmcecosse]

Actually - I suspect weak sparks under load - try a new condenser and reset the points gap.

[guymcc]

Thanks for all the suggestions guys.

When I get a chance to look at her then I'll start with the diagnosis from these helpful tips! Then n doubt come back with some more questions!

[chickenjohn]

Sounds like the points have closed up or as Roy said, weak condensor.

Check the points gap first.

[guymcc]

Hello all! Been too long!

Finally started having a look round the problem. So I've started with the spark plugs... They are black! Definitely! So I gave them a wee clean with some emery paper. Went for another run and maybe felt marginally better. But this won't be the cause of the problem.

So next up is to check the carb piston to see if it rising and falling correctly.

Thoughts on the black spark plugs would be great. TIA

[mike.perry]

Running rich. Try getting up to operating temp then adjusting the carb mixure nut.

[guymcc]

Ok so been out for a run and established that the spluttering only happens under load.

Also the carb piston is lifting with a bit of pressure and falling under its own steam.

How is the carb mixture nut done? Which bit am I looking at? Cheers!

[JOWETTJAVELIN]

Did you ever put fresh petrol in it after such a long lay up, or is it the old tar still in the tank?

[guymcc]

Petrol wise it sshould be fine, it's had a couple of fresh tanks and the problem is still there. It will be and easy fix for someone. It will just take me a bit of time to do my wading of the Haynes and wading on here and asking questions!

[guymcc]

Ok so been doing a bit of reading and this thread has caught my eye! I may try and have a look at this tomorrow!

Any thoughts?

http://www.mmoc.org.uk/viewtopic.php?f= ... s&start=15

Cheers!

[bmcecosse]

Running rich will just eat up petrol, and 'bore wash' the engine causing massive wear..... Start by removing the air cleaner element - is it clogged with oil fume and flies? Does the car run any better without the paper element in the case??

[guymcc]

I went for a short run with the air filter off, and still the same, stuttering under load. It was a short run though. Would I need to take it for a few miles so that things worked in, settled down, as it were? The air filter seems fairly clean. I will take some photos tomorrow of spark plugs and inside of distributor cap, plus air filter, see what people think.

[bmcecosse]

Is the fuel level too high in the carb? If you switch on the Ignition - does the pump 'tick' continuously?

[guymcc]

The pump clicks a few times slows then stops.