Head scratcher.

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Post by SRF » Sat Sep 22, 2018 6:44 pm

My SE5 has had a mysterious fault. When it starts it doesn't run on all cylinders for several minutes. I have done a cylinder compression test they are all within 5 psi of each other. valve clearances spot on. I have replaced the distributor cap rotor arm, spark plugs and the leads are almost new. I have rebuilt the carb and replaced the W plate which was cracked. Before I pull the heads off is there something I am missing.


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Post by rebel alliance » Sat Sep 22, 2018 6:57 pm

What are you hopeing to find by pulling the heads off ? If you have good compression the valves and rings would appear to be ok..Try pulling different plug leads off first to see if its the same cylinders not fireing every time you start it.Which Rapier have you ?



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Post by scimjim » Sat Sep 22, 2018 6:59 pm

Any play in the dizzy shaft? Do you know which cylinders aren’t firing?


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Post by kapri » Sat Sep 22, 2018 7:14 pm

" leads are almost new" ...don't let that fool you :(



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Post by Old and Slow » Sat Sep 22, 2018 9:04 pm

Sounds to me like an electrical problem;
Do the plug caps need replacing?
Have you checked the plugs? One should be wet if it isn't firing on that cylinder; are they "warm" plugs or cold? Close all the plug gaps and see if this makes a difference (i.e. a weak spark?)
The wobbly dizzy shaft is worth checking.
Lubricate the pivot for the points, it might be sticking.
Fingers crossed you get to the bottom of this - very annoying.


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Post by philhoward » Sat Sep 22, 2018 9:24 pm

I’d guess the autochoke isn’t doing quite what it should?


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Post by SRF » Sat Sep 22, 2018 9:27 pm

No points, electronic module. I had a 3a Rapier, the only car I regret selling. I will try pulling each lead in turn, some how forgot to do that. Manual choke Phil


Ray

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Post by philhoward » Sat Sep 22, 2018 9:43 pm

DGMS or a converted DGAS - and if converted, how was it achieved?


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Post by rebel alliance » Sat Sep 22, 2018 9:53 pm

3a nice, series 5,s were my favourite, know what you mean about regreting selling....sod it i'm buying another 😊



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Post by SRF » Sun Sep 23, 2018 3:11 pm

well I never, I removed the air cleaner to get a better view of the ht leads and the fault cleared. I think what is happening is that the original air cleaner sits very close to the top of the distributor especially no 5 lead, somehow this is grounding the spark before it gets to the plug. I am going to make a thicker rubber gasket and stick some rubber on the underside of the filter canister where is gets close to the dizzie. I have had enough under bonnet pyrotechnics thank you.


Ray

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Post by Scimher » Sun Sep 23, 2018 3:26 pm

Hope that sorts it, Ray......



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Post by Coupe Racing » Sun Sep 23, 2018 3:54 pm

Ive seen something similar before too


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Post by SRF » Sun Sep 23, 2018 4:44 pm

Does anyone know of an aftermarket filter that would fit easily.


Ray

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Post by AJL Electronics » Sun Sep 23, 2018 7:02 pm

SRF wrote:
Sun Sep 23, 2018 4:44 pm
Does anyone know of an aftermarket filter that would fit easily.
You are masking the symptoms. Replace the HT leads with some quality ones, or if you can't run to that, at least the lead that has been tracking as it is now u/s.


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Post by Coupe Racing » Sun Sep 23, 2018 8:26 pm

I made a small spacer to raise the filter and also isolated the underside of the filter


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