Spluttering and backfiring

[Roy Hudson]

Thought I would give the mgb roadster a quick run today but when I tried starting it up it began spluttering and struggling ( like it was running on three cylinders ) and backfiring out of the exhaust
Looking for a bit of inspiration if anyone has any ideas

[Peter Cresswell]

Hi Roy,
The first thing I would do is try some fresh fuel. Modern fuels with Ethanol don't have a long shelf (or should that be tank?) life, can be less than 3 months before it starts to degrade I believe. Add about the same amount again in fresh Super-unleaded as you already have in the tank. Try this before you start taking things apart or making adjustments!

[Roy Hudson]

Thank you Peter
I will take your advice and give it some fresh fuel , it doesn't seem to want to run so I will have to put 5 litres in and try it again before I can run it to the fuel station .

[Peter Cresswell]

Hi Roy,
If the fresh fuel doesn't help, some more details might help everyone who contributes to the forum to provide further advice. So if you need to, let us all know:
1. How long has it been since the car was last started?
2. Do you hear the fuel pump ticking, initially very fast then slowing to a tick about every 15 seconds?
3. Can you smell petrol when trying to start it?
4. Did it run smoothly and normally when last used?

I think these pointers would help identify your problem if the fresh fuel doesn't help. Remember it might need a few miles to clear itself.

[Roy Hudson]

Hi Peter thank you for your advice so far
The car was starting and idling perfectly on the Wednesday evening in the garage , then when I tried starting it on the Saturday evening it just started splitting and backfiring and was definitely not firing on all 4 cylinders.
Just had the nationwide recovery guy out to it and he was absolutely useless ( said he couldn't help me because he didn't have a new coil pack to try )
The car has lumenition electronic ignition fitted if this helps ?
Regards
Roy

[Peter Cresswell]

Hi Roy,
I notice from your other posts that you have not owned the car for long, and it is one of the last LE spec cars. Sometimes it helps if you provide your general location within your profile as another member living close by might be able to help you to resolve your problem.

Assuming some new fuel hasn't changed the problem, when you started the car last Wednesday, did you start it and leave it running for a little time (say up to 5 minutes) or did you it take for a reasonable run (say 10 miles)?

If it was just a start up without a run, I am thinking that there may be a condensation problem (the weather has been somewhat damp lately!), which is affecting the ignition leads somehow. This might be inside the distributor cap, or on the outside or on the leads if they are touching one another. To localise this firstly take a visual look at how the leads 'sit' with each other. If any are touching, then try and move them apart. Using a pan scourer (from the kitchen!) will help with this, then try starting it again. You could also try starting the car in the dark to see if there are any sparks between the leads. If the result is the same misfire/backfire (or there are no visible sparks when starting it in the dark) then move on. If it is ok the you need to get either some ignition lead spacers or new leads.
If the misfire still exists then try spraying the outside of the distributor cap with WD40, as this will disperse any moisture, and may solve the problem. If it still exists try spraying inside the distributor cap and again try starting to see if it clears. If either fixes the problem you might need a new distributor cap, in which case make sure you order one for a late model car (I think they are a 45D4 distributor and have a different cap from the earlier ones).

If you took the car for a run on Wednesday, then we might need to think some more. If it was running fine then, there is no obvious reason why it shouldn't run right now!

Personally I have had a few cars (but not MGs) fitted with Luminition systems and they haven't given any problems but I did encounter a problem with the ignitor type system (not Luminition but the Luminition Magtronic is this type) but then the car wouldn't start at all. I have had several 'older' MGs ( 3 x MGBs, 2 x MGAs and an MGC) all with standard ignition systems and they have been very reliable at starting.

One further thought, did you buy the car from a dealer or privately?

Let us know how you get on!

[Roy Hudson]

Hello Peter
Thankyou again for giving your time to help solve my problem , it is much appreciated
I will update my profile asap , I live in Rossendale Lancashire and bought the car from Graham Chapman classic cars who described the car ( runs like a new car ! ) I have a feeling you might be right about the damp issue as I seem to recall it being a wet damp evening.
The car was delivered on a trailer so I have not had a chance yet to give it a good run out
I will check the leads like you said and let you know how I get on

[Peter Cresswell]

Hi Roy,
It could have been standing around at Graham Chapman's for a little time, so try the new petrol first, then the ignition side. Might be worth a call to Graham to ask how long it was in stock, as it doesn't run right....!

[Roy Hudson]

Hi Peter
A quick update and much better news , I checked the HT leads like you said and took each one off and visually inspected it ,whilst they looked ok a couple of them have a damaged connector on the plug side and I cannot get them so they don't touch each other though ? . I then cleaned each plug and refitted them , when I started the car up it no longer backfires and sounds much healthier ( still not as smooth as I would like though but a hundred times better ) I am going to order a new set of leads and might invest in a new coil as well
Really appreciated the help though , thankyou again
Roy

[ROGER COOPER]

Just a little worried, chaps, about the use of a pan scourer to separate HT leads. Did you know there are metallic pan scourers as well as the plastic ones? - and, NO, I don't mean Brillo Pads.
Can't be a barrel of laughs holding a metal pan scourer between two HT leads with poor insulation!!