Misfire and then stop until cool

Talk about the E-Type Series 3
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andrewh
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#1 Misfire and then stop until cool

Post by andrewh » Sun Apr 22, 2018 2:51 pm

Chaps, I have a 1973 4 x stromberg carb XJ12. So pretty much identical to the series 3 V12. It has developed an annoying habit of starting to misfire and stop after about 5 miles ( when hot ) and will not go properly until its pretty cool again. I am fairly sure it will be ignition, but not sure which bit to test and what a test schedule should be. Its had the SNG Barratt upgraded opus replacement about 10 years ago. Is there a test schedule for the Ballast resistor, amplifier and coil? I am sure there is one of you experts will have the solution I feel sure. thanks in advance.
1962 3.8 Series One FHC

http://etype860897.blogspot.com/

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lowact
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#2 Re: Misfire and then stop until cool

Post by lowact » Sun Apr 22, 2018 3:05 pm

On V12E you can get these exact symptoms if yr fuel filter is blocked. All the crud collects on the inside so u can't tell by looking, have to pull the filter apart.
Regards,
ColinL
'72 OTS manual V12

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#3 Re: Misfire and then stop until cool

Post by andrewh » Sun Apr 22, 2018 4:09 pm

ok, well thats an idea. I shall take a look at the filter, its quite possible and would be cheaper than any of the ignition units. Although quite hard to fathom out why it would manifest itself when warm and run again when its cooled down. thanks for the suggestion, and definitely worth checking and changing anyway i guess.
1962 3.8 Series One FHC

http://etype860897.blogspot.com/

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lowact
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#4 Re: Misfire and then stop until cool

Post by lowact » Mon Apr 23, 2018 12:37 am

If the problem is fuel filter the temperature is coincidence, it takes about the same time to warm up as it does for the fuel flow to pick up loose crud in the filter bowl and seal off the filter enough to effect performance at normal speeds, or at least that is the theory I came up with when it happened to me. Stop for a bit and it settles and clears. Overnight trip from Melbourne to Canberra, stop, wait, start, drive for a bit repeat, convinced it was ignition temperature, how stupid I felt on finding it was just the filter! On the plus side, fuel consumption was fantastic …
Here is filter cut open to show the crud
Image

If it is igniion, it also may be temp is coincidence, supposedly only the original Opus had temp issues, the replacments from SNGB, Reopus or the later CEI based, should be ok? Helpful if u knew exactly what iginition u have, or photos?
Regards,
ColinL
'72 OTS manual V12

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christopher storey
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#5 Re: Misfire and then stop until cool

Post by christopher storey » Mon Apr 23, 2018 8:48 am

It sounds typical of the conductive rotor arm problem which has been around for some years, where as it heats up the bakelite in the arm becomes conductive and shorts the HT to earth. I should try a new rotor from the Distributor Doctor - make sure you get it from him and not one of the fakes ( unbelievable isn't it ) which have sprung up

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#6 Re: Misfire and then stop until cool

Post by andrewh » Mon Apr 23, 2018 4:30 pm

Ah, ok. Thats an idea but it has worked fine for a long while. I hate these sort of issues, can take for ever and cost a small fortune! thx Christopher.
1962 3.8 Series One FHC

http://etype860897.blogspot.com/

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Woolfi
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#7 Re: Misfire and then stop until cool

Post by Woolfi » Mon Apr 23, 2018 4:40 pm

A friend in Germany hat exactly the same proble last friday. Working and testig all saturday, he found a corroded cable connection in the ignition system. He cleaned this and all was okay.
Maybe this is also your problem, but this is far away to be shure.
Regards Wolfgang Gatza

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#8 Re: Misfire and then stop until cool

Post by andrewh » Mon Apr 23, 2018 4:42 pm

ok, thanks. Yes I think I need to go through a few things. Its just annoying as you have to go for a drive to see whether it breaks down or not, then you have to wait for 20 minutes to come home!!
1962 3.8 Series One FHC

http://etype860897.blogspot.com/

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christopher storey
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#9 Re: Misfire and then stop until cool

Post by christopher storey » Mon Apr 23, 2018 5:26 pm

Andrew : you can often test the rotor arm for conductivity by temporarily interposing a layer or two of cling film between the arm and the distributor shaft . If this cures the problem, then it is very suggestive of the arm having become conductive. Incidentally, the fact that it has worked for a while before this problem arose does not necessarily mean that it is ok : I don't know the chemistry involved, but the problem is not always instantaneous, and can develop over a period , presumably with repeated heat cycling

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#10 Re: Misfire and then stop until cool

Post by andrewh » Sat Apr 28, 2018 11:59 am

thanks Christopher. Sorry for the late reply. I shall have a look. To be honest, I have not done anything to it since its failure to proceed on drive it day! Have dug my manual out and there is quite a bit about resistances etc on the amp and ballast resistor. I hope its broadly similar to the SNG kit, as they didnt get back to me about that. I can try out my new ( old ) AVOmeter.
1962 3.8 Series One FHC

http://etype860897.blogspot.com/

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