MGB Ignition Woes
Discussion
Hello all,
I am having problems with my '77 MGB. I have recently fitted Lumenition Optronic ignition and the car has now started running rough once it gets hot - misfiring and spluttering. I was idling well and had a slight misfire, as i am not sure i had the timing set perfectly after the install, but then almost suddenly it just struggled to idle and got worse.
I have swapped out the coil, and the new coil doesn't get as hot as the old one did. I put a timing light on. It was really advanced and I can get it to start, but it is struggling to idle at any static thing (5/10/15/20).
It is cooling down now, then I'll try again, after setting the valves.
Any ideas?
Richie.
(The worst bit is - it was running pretty well before the switch to Lumenition)
I am having problems with my '77 MGB. I have recently fitted Lumenition Optronic ignition and the car has now started running rough once it gets hot - misfiring and spluttering. I was idling well and had a slight misfire, as i am not sure i had the timing set perfectly after the install, but then almost suddenly it just struggled to idle and got worse.
I have swapped out the coil, and the new coil doesn't get as hot as the old one did. I put a timing light on. It was really advanced and I can get it to start, but it is struggling to idle at any static thing (5/10/15/20).
It is cooling down now, then I'll try again, after setting the valves.
Any ideas?
Richie.
(The worst bit is - it was running pretty well before the switch to Lumenition)
That may be the next step. Oh, it's a bank holiday. Boo.
Anyhow, just adjusted the valves and set the timing (again) and it runs, but there is still a tiny misfire are the initial point of throttle. I am wondering if it is just because it has cooled a little.
I am going to go for a spin and see if it is still there.
Thanks for your help.
Anyhow, just adjusted the valves and set the timing (again) and it runs, but there is still a tiny misfire are the initial point of throttle. I am wondering if it is just because it has cooled a little.
I am going to go for a spin and see if it is still there.
Thanks for your help.
if you get a new HT lead set - always a good idea if you don't know about the present ones - these are very good indeed I was very impressed with these as an upgrade from 2 and a half year old silicone leads and the company is impressive with good customer service - performanceleads.co.uk
you may not have heard of them because they’ve not long been doing retail but check out what they do here – Fastlane
P&P isn't cheap but they're still very good value even allowing for that as they are very god lead sets
Misfire –
you’ve done tappets so it’s check plugs and HT leads (and their boots and 10 connections, burp boots) then check timing again and finally the mixture and set up of carbs
check all wires and connections are clean, secure and protected – you might have disturbed something
also check the small delicate igniter wires inside dissy head that they are not knicked or rubbing or moving about with too much or too little slack
check those small delicate igniter wires outside the dissy head that they are not knicked or rubbing or moving about with too much or too little slack
you could go back to what was fitted previously to possibly confirm if the new stuff is faulty or damaged
bear in mind although the igniter head is new the dissy is not and possibly has not been oiled and lubed as required at services so do that if you’ve not already done so
oh, what about dissy cap is that new - a new ingniter with new dissy cap and new HT lead set would set you up for a few years then it's plugs as service items
ETA: big thumbs up for 123 dissys
you may not have heard of them because they’ve not long been doing retail but check out what they do here – Fastlane
P&P isn't cheap but they're still very good value even allowing for that as they are very god lead sets
Misfire –
you’ve done tappets so it’s check plugs and HT leads (and their boots and 10 connections, burp boots) then check timing again and finally the mixture and set up of carbs
check all wires and connections are clean, secure and protected – you might have disturbed something
also check the small delicate igniter wires inside dissy head that they are not knicked or rubbing or moving about with too much or too little slack
check those small delicate igniter wires outside the dissy head that they are not knicked or rubbing or moving about with too much or too little slack
you could go back to what was fitted previously to possibly confirm if the new stuff is faulty or damaged
bear in mind although the igniter head is new the dissy is not and possibly has not been oiled and lubed as required at services so do that if you’ve not already done so
oh, what about dissy cap is that new - a new ingniter with new dissy cap and new HT lead set would set you up for a few years then it's plugs as service items
ETA: big thumbs up for 123 dissys
Richie, hope all's well + just read the thread. Is all okay now? The small misfire could be the old girl either needing a good run to clear her bits, small adjustment to carbs, or small adjustment to timing though you've said you've covered this. BTW, are you running an SU fuel pump with contacts or a 12v constant pump?
hi andrew.
it's still misbehaving. it seems to be intermittant, varying from the slightest of misfires at the first touch of the throttle only, to the full-on popping/banging/kangaroo hopping. if anything, it's worse below 3000rpm and seems to happen uphill. it seems to only happen after warming up, too.
boy - It doesn't seem to be affected by the timing, either. i took the dizzy out when I put the lumenition in, and set it statically, then with a light.
na - i have order a set of leads from perfomanceleads - thanks.
i will put the new leads on, and have another look at the internals of the dizzy, but i think that is pretty much everything replaced. as i mentioned, it was running really well before the switch to lumenition, so i am a bit annoyed and a bit stumped.
thanks again for your help.
it's still misbehaving. it seems to be intermittant, varying from the slightest of misfires at the first touch of the throttle only, to the full-on popping/banging/kangaroo hopping. if anything, it's worse below 3000rpm and seems to happen uphill. it seems to only happen after warming up, too.
boy - It doesn't seem to be affected by the timing, either. i took the dizzy out when I put the lumenition in, and set it statically, then with a light.na - i have order a set of leads from perfomanceleads - thanks.
i will put the new leads on, and have another look at the internals of the dizzy, but i think that is pretty much everything replaced. as i mentioned, it was running really well before the switch to lumenition, so i am a bit annoyed and a bit stumped.
thanks again for your help.
okay, if not ignition/timing side it can only be fuel. with symptons being worse under 3000rpm indicates fault noticeable when under heavier load i.e. on pick-up.
1. are HT leads in right way, especially #2 & #3?
2. is the distributor vacuum advance pipe in place, fixed, and clear of obstructions?
3. re-check condensor install/operation.
4. are dizzi plate + advance springs in good condition
5. clean all internals of dizzi with wd40 - check for ease of assembly/movement
6. if now running lumenition you may like to open spark plug gaps a little for better combustion efficiency; say 1/10th increase
if all other electrical/timing areas are good then over to fuel...
1. any crud in float chambers?
2. re-check fast idle settings/balance between carbs +++ check linkage settings/tightness/balance as if somehow out of sync can throw up some interesting faults
3. piston springs and dashpot oil...are they both in good condition? change oil to lighter viscosity and/or 50-50 mix of 3in1+engine oil
4. any air leaks in and around manifolds...intermittent air leaks can give similar symptons to timing/ignition faults.
Q. are you running SU contactor pump or 12v constant unit??
1. are HT leads in right way, especially #2 & #3?
2. is the distributor vacuum advance pipe in place, fixed, and clear of obstructions?
3. re-check condensor install/operation.
4. are dizzi plate + advance springs in good condition
5. clean all internals of dizzi with wd40 - check for ease of assembly/movement
6. if now running lumenition you may like to open spark plug gaps a little for better combustion efficiency; say 1/10th increase
if all other electrical/timing areas are good then over to fuel...
1. any crud in float chambers?
2. re-check fast idle settings/balance between carbs +++ check linkage settings/tightness/balance as if somehow out of sync can throw up some interesting faults
3. piston springs and dashpot oil...are they both in good condition? change oil to lighter viscosity and/or 50-50 mix of 3in1+engine oil
4. any air leaks in and around manifolds...intermittent air leaks can give similar symptons to timing/ignition faults.
Q. are you running SU contactor pump or 12v constant unit??
v8250 said:
okay, if not ignition/timing side it can only be fuel. with symptons being worse under 3000rpm indicates fault noticeable when under heavier load i.e. on pick-up.
1. are HT leads in right way, especially #2 & #3?
2. is the distributor vacuum advance pipe in place, fixed, and clear of obstructions?
3. re-check condensor install/operation.
4. are dizzi plate + advance springs in good condition
5. clean all internals of dizzi with wd40 - check for ease of assembly/movement
6. if now running lumenition you may like to open spark plug gaps a little for better combustion efficiency; say 1/10th increase
if all other electrical/timing areas are good then over to fuel...
1. any crud in float chambers?
2. re-check fast idle settings/balance between carbs +++ check linkage settings/tightness/balance as if somehow out of sync can throw up some interesting faults
3. piston springs and dashpot oil...are they both in good condition? change oil to lighter viscosity and/or 50-50 mix of 3in1+engine oil
4. any air leaks in and around manifolds...intermittent air leaks can give similar symptons to timing/ignition faults.
Q. are you running SU contactor pump or 12v constant unit??
thanks. i will get out to the old girl this week and go over everything again.1. are HT leads in right way, especially #2 & #3?
2. is the distributor vacuum advance pipe in place, fixed, and clear of obstructions?
3. re-check condensor install/operation.
4. are dizzi plate + advance springs in good condition
5. clean all internals of dizzi with wd40 - check for ease of assembly/movement
6. if now running lumenition you may like to open spark plug gaps a little for better combustion efficiency; say 1/10th increase
if all other electrical/timing areas are good then over to fuel...
1. any crud in float chambers?
2. re-check fast idle settings/balance between carbs +++ check linkage settings/tightness/balance as if somehow out of sync can throw up some interesting faults
3. piston springs and dashpot oil...are they both in good condition? change oil to lighter viscosity and/or 50-50 mix of 3in1+engine oil
4. any air leaks in and around manifolds...intermittent air leaks can give similar symptons to timing/ignition faults.
Q. are you running SU contactor pump or 12v constant unit??
i am running an SU fuel pump. the thing has me convinced it is the ignition side is that the weekend before, i checked the mixture, balanced the carbs and checked the timing. it was running pretty nicely (i know)
the only things changed were tha alternator and the ingnition.
ooh - except, it did get pretty hot coming back to London on that warm weekend. not boiled, steam pi55ing out hot, but close to the red. she 'left her mark' when i parked up.
i will go over the carbs, as it does feel a bit like the choke has been left on (not that i've ever done that, of course!), or an air leak but i a, pretty sure they are sound.
thanks again, chaps.
It sounds as if it could be a failing rotor arm, possibly accelerated by increased voltage from the lumenition system -see http://www.distributordoctor.com/rotor_arms.html
benjj said:
It is probably not this but I suffered the exact same symptoms on a rally recently. After a bit of diffing around it was the simplest of things: the choke was not fully disengaging and it was running on about 1/8th choke. Worth a quick look at the very least...
Heh! I've done this too. Car came back from the garage having been serviced and adjusted. I used the choke as I used to and it drove like a dog. I have to remember to push the choke back in rather than just letting it go.Before. It has always overheated when warm and in traffic.
I have replaced everything apart from the fan and the heater core and have a new fan to fit this weekend.
I drove back from Sussex to London and got stuck in a traffic jam, and pulled over when it got to the red. It didn't boil. Two years ago, I was stuck in the famous silverstone traffic and watched it boil and spray yoghurt everywhere, so i am a bit paranoid about replacing a head gasket again.
I did drive it the next day, and it all seemed fine. I am certain the misfire developed after fitting the lumenition, but i am of course open to chcking everything.
I have replaced everything apart from the fan and the heater core and have a new fan to fit this weekend.
I drove back from Sussex to London and got stuck in a traffic jam, and pulled over when it got to the red. It didn't boil. Two years ago, I was stuck in the famous silverstone traffic and watched it boil and spray yoghurt everywhere, so i am a bit paranoid about replacing a head gasket again.
I did drive it the next day, and it all seemed fine. I am certain the misfire developed after fitting the lumenition, but i am of course open to chcking everything.
Richie,
a few things to cover so numbers sorry
a) if you still have a condenser(?) then new modern made replacements can be poor quality so buy new from somewhere like the Distributor Doctor
b) don’t spray WD40 inside the dissy cap, in fact use these instead of WD40 only have WD40 as a back up at home or small can in the boot:
electrical contact cleaner
· (thin) spray lubricant
· dry spray lubricant
· penetrating/releasing fluid (such as PlusGas)
· silicone lubricant (for rubber and plastics)
· carb cleaning spray
· anti-seize assembly compound (like Copper Ease)
· electrical sealing/protecting products (go find)
· light oil (3-in-one type)
· all purpose grease (and gun)
· cheap small brushes - to apply Copper Ease, grease, ect.
personally I like the lubricating sprays with PTFE
c) never assume new parts can’t be faulty and that the parts fitted are correct or original type
d) check the choke out, except perhaps for the last 1/8” it should pull itself back that’s why you have to twist to lock it
if you could also do me a favour and let me know if the performanceleads make any difference even if they don’t cure the misfire – to do this of course they must be changed in isolation to determine that it’s them and not any other thing you’ve changed
a few things to cover so numbers sorry
a) if you still have a condenser(?) then new modern made replacements can be poor quality so buy new from somewhere like the Distributor Doctor
b) don’t spray WD40 inside the dissy cap, in fact use these instead of WD40 only have WD40 as a back up at home or small can in the boot:
electrical contact cleaner
· (thin) spray lubricant
· dry spray lubricant
· penetrating/releasing fluid (such as PlusGas)
· silicone lubricant (for rubber and plastics)
· carb cleaning spray
· anti-seize assembly compound (like Copper Ease)
· electrical sealing/protecting products (go find)
· light oil (3-in-one type)
· all purpose grease (and gun)
· cheap small brushes - to apply Copper Ease, grease, ect.
personally I like the lubricating sprays with PTFE
c) never assume new parts can’t be faulty and that the parts fitted are correct or original type
d) check the choke out, except perhaps for the last 1/8” it should pull itself back that’s why you have to twist to lock it
if you could also do me a favour and let me know if the performanceleads make any difference even if they don’t cure the misfire – to do this of course they must be changed in isolation to determine that it’s them and not any other thing you’ve changed
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