Can't remember the last time I saw a coil buried under a dashboard though, Love to know why it was put there in the first place ?
Hi All,
I have a Ginetta G27 that has developed a misfire (I am assuming / hoping it is electrical at the moment).
It has a silver top with twin 40 webbers... The tickover has dropped with a petrol rich smell coming from the exhaust and it is not pulling as well as
it was. The car is not running as hot as it used to as well.
The spark plugs are new. I have replaced the misab plates as the were old and leaking a few months ago. The car passed the MOT a month ago and this
has only developed since and I have only drive around 80 miles since due to the crap weather we have had.
One of my first thoughts was to look at the leads (after checking the spark plugs to see which cylinder was the culprit). The leads lead through the
engine bulkhead and I cant easily see where they go... how easy is it to access this area to change the plug leads?
Alex
I would do a compression test first then check the ignition over. Then check the carbs.
I assume they were balanced after misabs were changed, but sometimes they need more than one tune.
Will check the compression as you suggest... but can not see the ignition as it runs through the b'head
Further to this I replaced the misabs after the tune as the leaks were only very minor and appeared when the engine was very hot.
Agreed it could be compression problems however the failure would need to be severe as it seems to be not firing at all on one cylinder from the smell
of petrol in the exhaust and this led me to ting it is ignition.
Alex
I went to a friends to balance the webers on his Tiger this week and it was a bit rough. So tinkered with it a bit but decided to check the compressions. All plugs out, started to test number 1 and had a solid jet of water shoot out number 4! Whipped the head off and the gasket was broke between waterway and combustion chamber. Always pays to know the compressions are right first, can save a lot of time.
good point and will test this weekend
Tested the compression and they are all the same within 5psi anyway.
Also seem to get a good spark from all the leads - or seems like it as I can hear sparks coming from the leads to the plugs on all of them.
The culprit is the most forward piston. I pulled the lead of this spark plug and there is no difference to the misfire.
One thing I did notice is that there is considerable water at lower temps... so possibly the thermostat could need replacing however I do not think
it
Any suggestions??
Alex
You took the plugs out to do the compression test, did you notice any difference in colour between the plugs? If you feel the problem is number 1 cylinder, swap that plug for number 4 and see if the problem is still number 1. What were the compression readings?
The compression readings were all around 90psi +/- 5 however this was not a "real" number as I do not have a valve on the extension for the
compression tester.
No 1 plug was very black... good idea on swapping the plug. They are only a few months ol and the were changed when the car was tunned at on a RR but
I guess this plug could be faulty. I was told the engine was in good nick by the guy tuning it and I was seeing 145hp at the wheels (170ish at the
engine).
Alex
So if you swap number 1 plug with number 4, is there a difference? does number 4 become the 'weak' cylinder. The compression pressures, I would expect to be significantly higher than 90. Both my ST170 and Pinto are over 150.
First step with a single cylinder misifre on twin DCOE's is always clean the jets for the affected cylinder also check the cold start
mechanism (choke) is working and returning fully ***** even if it is not connected to a cable *****.
Next step is to check the plug leads, plug and coil properly. Ford use extremely wide spark plug gas the result is spark voltages of up to 35kv at
full throttle in contrast with the 15kv which was typical back in the day. 35kv puts immense electrical stress on the insulation.
The rule of thumb is in normal air at atmospheric pressure 1mm = 1kv so you need to actually see the spark jump 30+mm at the end of the
plug lead, even if the lead and coil pass this test you should do a continuity and ressistance test on the lead with a multimeter -- see official
NGK method here https://www.ngk.de/en/technology-in-detail/ignition-cables/diagnosis/testing-of-ignition-cables/
The other spark lead tests are shown on this page http://www.wikihow.com/Test-Spark-Plug-Wires
[Edited on 16/7/16 by britishtrident]
Thanks for the suggestion
Will check the choke (it has one fitted) though I do not use it at all.
Any guides on how to clean out the jets? If they were blocked would it run lean rather than what feels like flooding.... I am getting pops from the
air intakes and the exhaust smells of petrol.
Just on feel I would say that the around 30mm ish sparks from the leads. It is really hard to check the leads as they run through the engine bulkhead
and at the moment I have no idea on how I replace them - I can only just reach the coil when lying in the foot well and I suspect i will need to
discontent the dash to get proper access.
Right found the solution after the following:
Changed the fuel lines (were perished and leaking fuel) - I know that it might not make any difference but they were perished and leaking like a
sieve!
Changed the thermostat - was sticking open and I am sure it was not helping the eng get to temp. Drilled a hole in the new one to help it get to temp
with my fuel rail.
Cleaned carbs out with IPA and sucked and deposits out
swapped plugs around and noticed that I was getting a popping sound that followed the movement of the plugs.
One of the plugs was faulty even though it was one a couple of months old and with 300 miles on it :=(
The original were fitted by the tuning company and were std NGK TR5A10... Are these OK plugs? The new one I replaced it with was PTR5A10 (Platinum)
Thanks for the help BTW!
Cheers
Alex
ok - so I thought I had fixed the misfire but I had not.
Overview of the situation
- Silver Top with twin 40 webers and fast road cams
- manual choke - that does not get used
- all the spark plug gaps aree at 0.7mm - had a dodgy new one that was replaced
- misabs have been replaced
- Has been RR'ed last year at around 145 to 155hp at the engine and at the same time had the webers balanced etc
- I have replaced the leads and plugs
- Cleaned out the carbs and jets with Isopropyl alcohol
The engine starts OK and for the first 10mins or so the tickover is OK at around 900rpm
When driving the car seems to be running fine and does seem to pull well - which it should with this hp.
As the engine gets fully warm it seems to tickover OK at 900rpm but this slowly reduces until it dies.
Odd thing on the compression is that all the cylinders are reading 85 to 90psi...! Thought is was the testing kit was not measuring correctly.
Picture of spark plugs is as below with the upper plug the aft plug and the lower one(blacker) is the front plug
https://photos.google.com/share/AF1QipP3QSKwJVHm4Lp7pReo0e3aKo7_gVbo1UPYuyX-cctKLsc8gs-xKUn7IDrVDtaGCA?key=ZGxmWjZjYlUzVXd1ZEtmUUltcjF1WGtJQkQ4bHNR
Any ideas?? What is odd to me is that all the pressures are low. If it was worn rings or valves they would be all different - wouldn't they??
Could the timing be out? But is this is the case, how come it is still performing OK on the RR.
Could it still be I am not getting correct pressure reading and it needs tuning again...
I am not convinced a new plug can be faulty - they are simple as can be - made from a lump of insulating ceramic with some metal through it - so what
can possibly go wrong?. More than likely it is contaminated with soot due to not firing, but that's neither here not there.
Tell us more about the ignition - is it distributor - points or electronic? One coil or multiple e.g. EDIS?
How is timing set?
Your latest post is 6 months after the "fixed it" post so what you see now may be a different problem?
[Edited on 30/1/17 by 02GF74]
I think it is the same problem and I was just persuading my self that it was fixed... also only did runs on faster roads and not in traffic / town
till the weekend when it was obvious all was not right.
Timing is electronic...sorry no idea if multiple or single coil. How can I tell?
I am getting what feels like good sparks from each lead
No mention of a coil pack being or new leads
checked if it's a std ford one they fail regularly and carb dirty / balance issue
quote:
Originally posted by AlexXtreme
Timing is electronic...sorry no idea if multiple or single coil. How can I tell?
quote:
Originally posted by AlexXtreme
I am getting what feels like good sparks from each lead
- for combustion the engine needs fuel, air and a spark - if it is not firing, then there is issue with one of
those. Will post a picture of coil - the coil is under the dash and access is not easy. The leads are new
The problem happens when the car reaches normal temp around 90c
It always occurs and seems to be at the front of the engine - as you can see from the plugs it looks as though the plugs get darker from no 4 to no
1
Once the misfire has started I can restart the engine and it continues to misfire
[Edited on 30/1/17 by AlexXtreme]
these are the best pics of what I assume is the coil.... I can not get to it without either taking the steering wheel off or removing the dash
https://goo.gl/photos/xye394GLEojMCWQS7
https://goo.gl/photos/rZUrJitAfW42nei89
Alex
It looks like a standard Ford coil pack from what I can see , they are sometimes problematic but cheap enough to replace if suspect . When you tested the compressions did you remove all plugs from a hot engine and crank it over with the throttle fully open ? Also after finding low compressions put a teaspoon full of engine oil down the plug hole and repeat the compression test, anything over about a 10% increase indicates worn rings etc . I had problems years ago with a silver top engine that had a rough idle when hot , the compressions had been tested several times all showed up as good . A simple cylinder leakage test showed up a leaking inlet valve. Another problem I've had was the hydraulic tappets pumping up do to excessive oil pressure caused by a pressure relief valve fault. Incorrect oil can cause problems , what oil are you using? It might be worth checking the valve timing?
Yes the engine was hot and all plugs remove.... but the throttle was closed! I guess that will be the reason!
I use 3 w 30 oil and will try a drop if the throttle makes the difference.
I thought about the timing however I would not the power I am seeing if the timing was out.
Thanks Rusty!
I suspect it is something to do with the carbs and have provisionally book the car into a tuner I know on the 21st Feb... does anyone have any
recommendations for a tuner who knows their carbs around the Southampton area? The guy I know lives in New Milton
New plugs new leads so try a replacement coil pack, and check all wiring, remove plugs clean contacts, squirt a drop of wd40 and reconnect. Also check and clean all earths.
Was going to say leads as they can be a problem on these
If its playing up when the engine is warm/hot, try a new coil first
Changing the coil is going to be the last report as it is so much work to do!
Are coils really that un-reliable? I can imagine in the engine bay where it gets warm I can imagine it not lasting long, however mine is under the
dash board, only sen 16k miles over 16 years and by the looks of it has been garaged!
The only way your going to know for sure if the coil pack is the problem is to change it.
quote:
Originally posted by AlexXtreme
Changing the coil is going to be the last report as it is so much work to do!
Are coils really that un-reliable? I can imagine in the engine bay where it gets warm I can imagine it not lasting long, however mine is under the dash board, only sen 16k miles over 16 years and by the looks of it has been garaged!
quote:
Originally posted by perksy
Typical symptom of a faulty coil is it 'breaking down' under load when the engine is hot
The
coil dissipates a fair amount of heat and will get hot enough so you cannot hold it in your hand. That's what I meant, Honest
Can't remember the last time I saw a coil buried under a dashboard though, Love to know why it was put there in the first place ?
the leads were part custom.. the spark plug end was supplied fitted and i made up the other end my self under the dash. They route through a hole in
the dash which I sealed with silicon to stop the rubbing / getting damaged. It was a long job and when I had finished - no difference.
The only reason I can think of that the coil is under the dash is that the engine is mounted further back that std with which left little room to
mount the coil other than under the carbs which would give an even longer route for the leads and keeping out of the eng compt would keep it cool.
Will have a think about changing the coil.. :-(.
ok. my last comments on this.
Basically I suggest you get the spanners, screwdriver and drill out and relocate the ignition module to the engine bay where it belongs. I find it
hard to believe there is no room in the engine bay and having 15 kV zapping about in the occupants' compartment is not the best idea 
. If
necessary, relocate the battery into the passenger footwell to make space, unless already done. I don't believe there will be any issue with
temperature, after all, isn't the engine bay the place where car manufacturers put the engine's ignition gubbins?!?!?!? It should make it
more accessible so will be easier for you and the AA man to work on.
You may find that you can use off the shelf ready made spark plugs - this will rule out any problems with the custom made ones - are you 100% sure
they are fully working? Furthermore they will not need to pass through any bulkhead hole - I assume they are bunched together to pass through one
hole (again photos of your set up would really help) - which is not great - you do not want ignition leads to closely run parallel to each
other.
I am more than happy to be corrected here but I do not believe your problem is due to carbs being affected by engine heat. The carbs flow cold air,
pass cold fuel, not to mention the latent heat of evaporation as the petrol is atomised so are kept cool. I need to check but am pretty sure there
should be an insulator between the manifold and the carbs - is there one? And petrol resistant o-rings are fitted correctly so there are no air
leaks?
So my recommendation is to spend a bit of time and money on replacing the coil pack, fitting pukka leads, relocating the coil pack, cleaning out the
carb jets, check the sensor for the ignition is working correctly, check electrical connections for the ignition before spending oodles of cash at the
tuning place, that should be the last resort if the problem is not resolved.
Good luck and report back on the cause of the problem.
quote:
Originally posted by AlexXtreme
the leads were part custom.. the spark plug end was supplied fitted and i made up the other end my self under the dash. They route through a hole in the dash which I sealed with silicon to stop the rubbing / getting damaged. It was a long job and when I had finished - no difference.
The only reason I can think of that the coil is under the dash is that the engine is mounted further back that std with which left little room to mount the coil other than under the carbs which would give an even longer route for the leads and keeping out of the eng compt would keep it cool.
Will have a think about changing the coil.. :-(.
Exactly as Mr 02GF74 says Imo.
ford coils are not known for being bullet proof and the whole custom plug lead situation sets alarm bells ringing. In my humble experience misfires
are 90%+ plugs, lead or coil related. Usually the last one I end up changing....
Firstly thanks for your helpfully suggestions.
I have brought a new coil and will tackle changing it as a first option and see if it makes any difference... if no difference will re-locate.
Agreed having the leads going through the bulkhead is not ideal however as the pic below shows, there is not much room... don't want to position
around the exhaust side as the whole area gets pretty warm - previous owner clad the shell in this area with insulation due to heat issues. On the
other side, the coil would have to go under the carbs which would require extra long leads...
max gap around the back of the engine is not much!
https://goo.gl/photos/D3QwCxwyJtk4hq21A
To be fair it does look a bit tight
Difficult to see in the photo, but if you made a bracket up to suit could you not mount the coil between the carbs and the bulkhead ?
Just my 2p but i'm not a great fan of 'homemade' plug leads so if you can alter things so that you can use standard ones it would be
more reliable in the future
If your HT leads use a screw on fitting at the coil end they could well be your problem as could badly crimped fittings.
the thing is that I when I changed the leads it made no difference so so not think it is the leads.
there is not more than 30 mm gap between the carbs, the rod for the bonnet release and the bulkhead... I can not get my hand or feel the hole where
the leads go through the bulkhead and definitely no room for a coil.
it was not a screw fitting at the coil - I had to crimp them on.
Alex
.... one month on, what's the story now?
right ... meant to give an update but no time.
- brought new Weber distributor
- looked at moving it but this would been loom extension and the mounting bolts for the bracket were not accessible without moving the engine.. in the
end it was easier to work on it under the dash - bloody horrible
- as I could not take the bracket off the b'head I had to take the dist. off the bracket... this took a complete weekend for 4 bolts after buying
new short stubby ratchet and flexible drive new LED inspection light (the best thing I have brought for years!). Still could only either look or feel
and not do both at the same time.
- the last bolt took approx 3 hours with lots of swearing.
- anyway it is replaced and sealed the leads with silicone where they went through the b'head to minimise the chance of chaffing.
what i did notice straight away was the car started much easier than previously - I guess much better spark so it looks as though distributor was on
the way - thanks everyone for this advice.
Car runs better in general although still lumpyish. I think I need to run it at higher ticker (1000 rpm) as when for an example radiator fan cuts in
the load almost stalls the engine. Something still not 100% right so as this would be the second time I have had to raise this... but much happier
than before.
I think I will get the carbs looked at again as something is not quite right there... does anyone know a small garage who knows their carbs in
Southampton. The guy I know is in New Milton which is quite a pain for me.